TAsao iJt'iiJiHJtlJi^H;;)!;*". ■,■■)'!, ir;^!a,ti-i^^^!Si*!i;i<;u!;v Military Sketching and^ Map Reading (jrr leves aiatmll MnimtBitis ffiibrarg Jlt^aca, Sfem fncit BOUGHT WITH THE INCOME OP THE SAGE ENDOWMENT FUND THE GIFT OF HENRY W. SAGE 1891 Cornell University Library TA 590.G84 1917 Military sketching and map reading, 3 1924 004 669 408 Cornell University Library The original of tiiis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924004669408 MILITARY SKETCHING AND MAP READING BY Capt. Loren C. Grieves INFANTRY Third Edition Revised and Eni^ahged WASHINGTON United States Infantry Association 1917 Copyright 1918 By Capt. Loren C. Grieves TABLE OF CONTENTS INTRODUCTION PART I.— MAP READING Lesson I Page Length of Pace or Stride 5-6 Lesson II Individual Scale of Paces or Strides 7-13 Lesson III Solution of Scale Problems 14-16 Lesson IV Miscellaneous Scale Problems .... 17-18 Lesson V Orientation, Distance and Direction 19-27 Lesson VI Conventional Signs 28-35 Lesson VII Relief Maps 36-42 Lesson VIII Method of Determining Difference of Elevation 43-48 Lesson IX Exercises in Contouring 49-52 Lesson X Visibility . 53-56 PART II.— MILITARY SKETCHING Lesson XI Flat Sketch 62-71 Lesson XTI Road Sketch . ... 72-76 lii vi Table of Contents Lesson XITI Position and Outpost Sketches 77-82 Lesson XIV Place Sketch 83-85 Lesson XV Miscellaneous 86-90 PART III.— PANORAMIC OR LANDSCAPE SKETCHING Introduction 91 Lesson XVI Delineations 92-94 Lesson XVII Delineations (Continued) 95-99 Lesson XVIII Outdoor Exercises ... 100-107 Lesson XIX Sub-sketch 108-110 Lesson XX Range Data 111-115 Appendix Suggestions for Training Camps . 116-120 PREFACE In writing this book an effort has been made to produce a text-book on Military Sketching and Map Reading meeting the requirements of the curriculum prescribed for educational institutions operating under the pro- visions of the War Department, also to meet the require- ments prescribed in the examination of candidates for commissions in the Regular Army and the Reserve OflScer's Training Corps, and to provide a suitable course for the officers of the National Guard, and thus stand- ardize the instruction throughout the service. In view of the above, attention is invited to War Department orders prescribing text-books. It has been the aim to produce a suitable text-book at the minimum price, free from all extraneous matter and yet completely fulfilling the requirements. The author acknowledges with thanks the valuable assistance rendered by Captain A. W. Bjornstad in co-ordinating the subject matter of the text to meet the requirements of the various branches of the military establishment. INTRODUCTION The first duty of the instructor is to eradicate from the mind of the student the mistaken idea of many that this is a difficult subject. Many have the idea that one must possess artistic abilities in order to become proficient. That is not true. Simply master the basic principles and apply them. Some may be able to turn in neater and more artistic sketches than others, but the reader is looking for facts, and, if the facts are shown, the sketch answers the purpose. The subject, in so far as this text is concerned, is divided into two parts. Part I treats of Military Map Reading, or, the classification of maps; the natural and artificial objects represented on the map; methods of interpretation and military uses of maps. Part II treats of Military Topographical Sketching, or the means and methods employed in making military road and area sketcheSj and the reports pertaining to them. It is enjoined upon the instructor to employ the means and methods suggested, and to anticipate the require- ments of each lesson as to equipment. Large classes may be instructed successfully by one instructor if the right methods are pursued. The suggestions given in the Appendix which pertains to training camps apply in so far as the equipment is concerned to the work in organizations and educational institutions. PART I LESSON I LENGTH OF PACE OR STRIDE Before taking up the subject of scales, the student should determine the length of his pace or stride. An accurately measured course of at least one thousand yards should be selected. A thousand yards on the target range will answer the purpose, or, if a target range is not available, a course may be measured, prefer- ably on turf rather than on a macadamized road or side- walk. While pacing, one should take an easy, natural, and uniform gait. This is important as there is always a tendency on the part of the beginner to consider pacing and his natural gait as entirely distinct, which usually results in his first scale of paces or strides being too long. This may be obviated by pacing a sufficiently long course several times (four times is suggested), first impressing upon the student's mind the necessity of taking a natural and uniform gait. Let us assume that each student has paced the course four tim^s, and that his four results of pacing a course 1,000 yards long are: 1118 paces. 1109 " 1120 " 1117 " Total 4464 paces. 4464 -e- 4 = 1116 paces (average number of his paces for 1,000 yards) . To determine the length of his pace in inches : 1,000 yards = 36,000 inches. 36,000-7-1116 = 32.2 inches, the length of his pace. Before computing the length of his pace, each student should present his results of pacing to the instructor for verification, and, if any wide discrepancies exist, the stu- dent should be required to pace the course again. To avoid error in pacing, the student should keep a record G Military Sketching of the number of paces by making a mark for each 100 paces. A pace tally may be used if available. A hand instrument known as a "Tallying Register" may be used in recording the number of strides, if a scale of strides is desired. To accurately determine the length of pace or stride of each student, without doubt, will occupy the time avail- able for the first lesson, and the construction of scales will be taken up in the next lesson. Review Explain, as to a beginner, exactly how to determine the length of one's pace or stride. LESSON II INDIVIDUAL SCALE OF PACES OR STRIDES. READING SCALES Having determined the length of our pace or stride, let us now consider the subject of scales of maps. It is very clear that the ground and all of the objects upon it cannot be represented as large on the map as they ac- tually are. They must be reduced in size. In other words, any distance on the map is a certain fixed part of the corresponding distance on the ground, and this re- lation between map distance and ground distance is called the scale of the map. The scale should be no larger than is necessary to bring out all of the required details. For example, it has been found that the scale, 3 inches = 1 mile (meaning that 3 inches on the map represents 1 mile on the ground), is the proper scale for "Road Sketches." It gives just enough room to insert all of the details of military impor- tance, while, if we were to use the scale, 1 inch = 1 mile, for "Road Sketches," there would not be enough room, and by using the scale 6 inches = 1 mile, we would burden our- selves and those reading the map with an unnecessary amount of paper. There are three ways in which the scale of a map may be represented. 1st. A plain statement, as, for example, 3 inches equals 1 mile. 2nd. Represented by a fraction. To determine the fraction representing any scale, as 3 inches = 1 mile, let the map distance be the numerator and the ground dis- tance the denominator, BOTH TERMS OF THE FRACTION BEING OF THE SAME DENOMINA- TION, then reduce the fraction so that the numerator will be unity, as, for example: 3 inches on map 3 inches 1 Representative Fraction 1 mile on ground "63360 inches" 21120" (abbreviated R. F.) 8 Military Sketching 3rd. Graphically, in which the scale is actually repre- sented on the map, or on a ruler by a line divided into equal parts, each division being marked by the distance which it represents on the ground. There are two kinds of graphical scales: one for mak- ing the map, called a working scale, and one for reading the map, called a reading scale. If the same units of measure were used for both map making and map read- ing, one scale would answer for both purposes; but this is seldom the case, as we may obtain our distances in terms of paces or strides of various lengths depending upon the individual, while the party reading the map neces- sarily must have the distances expressed in terms of well- known units such as yards or miles. To CONSTKUCT A WoKKING ScALE OF PaCES Let us assume that a student has paced a course of a thousand yards four times with the following results: 1st result, 1118 paces. 2nd result, 1109 paces. 3rd result, 1120 paces. 4th result, 1117 paces. He wishes to construct a working scale, 3 inches on the scale representing 1 mile on the ground. To do so he should proceed as follows: 1st. Find the length of his pace. 2nd. Find how many of his paces will be represented by one inch on the map/. 3rd. Find the length in inches of his working scale. 4th. Construct the scale. 1st To Find the Length op His Pace (See Lesson I) 2nd To Find How Many of His Paces Will be Repre- sented BY One Inch on the Map 8 inches on the map = 63360 inches on the ground. 1 inch on the map =21120 inches on the ground. 21,120-7-32 = 660 of his paces. Individual Scale of Paces or Strides 9 3rd To Find the Length in Inches of a Convenient Working Scale Representing Say 2,400 Paces 660 paces = 1 inch. 2,400-5-660=3.63 inches, length of scale. To Construct the Scale Lay off the line AB (Fig. 1), 3.63 inches long, which represents 2,400 paces. Divide this line into 24 equal divisions representing 100 paces each. Divide the first one of these divisions on the left into five equal parts repre- senting 20 paces each. Transfer these divisions to a suit- able straight-edge ruler and the working scale is com- pleted. Working scales of 1", Q", and 12" to the mile may be constructed in a similar manner, also working scales of strides. To divide the line AB (Fig. 1) into 24 equal divisions^ lay off any line AC that can be conveniently divided into 24 equal parts. Draw a straight line connecting B and C, then draw lines parallel to BC as shown in the figure. These lines will divide AB into 24 equal divisions of 100 paces each. Use the same method for the divisions repre- senting 20 paces. The ruler shown in Fig. 2 is the most suitable for sketch- ing. It is made of a triangular, straight-edged piece of hard wood. A hole 3/8 inch in diameter and 2 inches deep may be bored into each end of the ruler and filled with lead to give it weight. This form of ruler furnishes a well-defined sighting line, and is the most convenient of any working scale yet devised. The material may be obtained by the instructor and cut into 6-inch strips, and, if practicable, filled with lead; or they may be obtained at a nominal price from the Book Department, Army Service Schools, providing the Book Department is fur- nished with the necessary data as to the various lengths of paces or strides desired. , After determining the length of your pace or stride, the working scale may be transferred to the ruler directly 10 Military Sketching Individual Scale of Paces or Strides 11 from the consolidated scales shown in Fig. 3 by placing the edge of the ruler on the proper line or interpolating between lines. This is sometimes found to be more practicable with certain non-commissioned officers than attempting to require them to solve the problems. A 1 I 1 1 I 1 I I 1 1 1 1 I 1 1 M 1 1 1 M 1 2 / 1 r r r / / 10 •90 20 200 71 <-?' / / / / Sg- '^^»?? N / A / / / / > \ \ \ \ V \ \ v^,^"- FicuQ Orientation, Distance, and Dibection 27 the needle is at N, then follow in prolongation of a line drawn through the pivot of the needle and the 63-degree point. The course is kept by an occasional reference to the compass which is held in front of you or placed upon the ground. Maps of various scales should be issued to members of the class, who should determine the distance in terms of yards, miles, or paces, and the magnetic azimuth between designated points in accordance with instructions given in this lesson. Questions for Review 1. What is meant by the expression, "orienting the map?" 2. What is meant by the true and magnetic meridians.? 3. What is meant by the declination of the needle? 4. What is the agonic line? 5. What are isogonic lines? 6. What is the declination of the needle to the east of the agonic line? To the west? 7. Describe three methods of determining approxi- mately the true meridian. 8. Describe two methods of orienting the map. 9. Describe two methods of locating your position on the map. 10. Describe the methods of scaling distances on the map. 11. What is meant by the magnetic azimuth of a line? The true azimuth of a line? 12. What is a protractor? 13. Describe the use of the protractor in determining the true and magnetic azimuth of lines. 14. Practical problems in determining distance and azimuth of points on the map should be given the class. LESSON VI CONVENTIONAL SIGNS Having learned how to read distances and directions on the map, we will now consider the many natural and artificial ground features of importance and the method of representing them on the map. In order that all may be able to read the map when completed, we must have some fixed method of repre- senting these ground features. With this in view the United States Geographic Board adopted, in 1912, a system of conventional signs for the use of all map- making departments of the government. At the close of the lesson are those that pertain to the work to be covered by this book. Members of the class should be required to reproduce these signs as neatly as possible, and this lesson should be devoted to that purpose. The instructor should superintend and criticise the work; especially should he avoid the usual tendency of making the signs too large. The ability to neatly reproduce these conventional signs should be included in the examination over this subject. When you find some idle moments with a pencil and paper at hand, your time may be profitably employed by practicing the con- struction of conventional signs. Just a few words about pencils would not be amiss at this particular point. The best for plotting are the hard kinds corresponding to Faber's Siberian HHHH and HHHHHH, especially for drawing fine lines and making points. For most kinds of work, a sharp-pointed pencil is used. For drawing long, straight lines, a chisel-pointed pencil should be used to produce a line of uniform breadth. For sketching and filling in conventional signs, softer pencils are preferable, such as correspond to Faber's HB. To keep the point always in good condition one should have a piece of fine sandpaper at hand for that purpose, 28 Conventional Signs <« u 8- I a I s I tf) §• .8 8 1 <« u j ^ ■i ° 5 « o e Jt : EH * I S I S I I I So 5 fi ig ft: 30 Mttjtary Sketching 1 1 'I o s 4 ! So J H i • "■ ,i i- i! i a i c c I a 5 c a Q c «0 » o c ■5 o 1^ k ^ ■5 c I, « I. *»0 « □ *0 c "a •*= S £ «k o a: (g S « .o € o s is ® I I I G o Conventional Signs 31 ^':>.<^ I >4 S t: ■^)h'^. ^ ^.- '.,4- •» - -5.' 5 g «f s I I • s • I I I e •a r "3 i r> ■8 MiuTAKY Sketching I o' o . c t o c. <* ■.b°oO „°c. 3' "O o .90 ."p: 00-, -;i^r feiif ;ii; fr ^ *■ -c- • «- <- f <0 o V3 o I ■0 O- A ^ "*■ -t-j^ ♦ + * "«- -f "<- 4 " *-^ lis a U * £» § •* ^ f r * ^ 6 1^ + ■<■ ♦ + i i i ' . ' ' ' £ ' <9 u ■« o c •D C 4) ■g c 5 2 t2 Conventional Signs 33 ^ St ^ {JtHiHHl Jl HJBOBBD =- o •« 3 ■g- I I I £ I I I! I o O o c I o u .5 f t" ^ ^ 5 6 § e 2 6 c J 9> t \ I ■S 5 «3 •B 2 o 3" ^ «0 « .c '5 2 c «3 4 3 E E o I* 4 m 11 3^ M J^^i-v; ,,<=!^pri .^ js- ,-.«.-■- 1 s I CO 3 'I I (0 ' o •4 34 MiLiTAKT Sketching «9 ^ m ■ 10 1j C 10 •S T •;= a. o o £ o '*: c ex,;; ^'-'fi---^^^ ooo.s'So^-oiooSoio;:;; Szzaao.cLOQ:iro:a>u}(Oco(Oio E J » m (9 -£ a « o t- — s» ? « ^1^ 10 CO X J _i 3 £ Z c a o J O ^ d a. o.' £ &0Z a tc iri n CO CO « I- I- N s o X < %l o - 5 < 01 CQ E •^. e H • » tr Ou i-nioaot.3 mmiDUuouou CO — -t: ?^':; CO '-'-2 S ■- 3"CJ*Jc'DWC(9_^ S £ £ cS S CO ± 5 T 5 C O XO -K '^ c a a a ? CO ♦; .. . ^ ^ i .-i'o •^ CO u Z .^. OC-U-VOOC.D..ID m1 • •- ' < a <^|D j)0^cj u ii LiO oouj uj^'u.co ^lOc*) : _• -? ji -I -J -1 /Z. «! JL o O S. « I 0) O L A 5 S -5 o .1 ? 10 w i « s s "8 o c « Conventional Signs 35 being careful to remove any lead dust from the point before using. Much more depends upon the proper sharpening, of a pencil, and afterwards keeping it so, than is commonly supposed. Most drawings to be inked are first constructed in pencil, the lines being made with as little pressure and as fine as is possible to show distinctly. LESSON vn RELIEF MAPS We have learned how to determine from the map the horizontal distances between points on the ground, the direction of one point from another, and the conventional signs representing the various terrain features, but, in order to have a better knowledge of the earth's surface, we must have some method of rapidly determining eleva- tions. In other words, we must know how high the hills are and how deep the valleys are. This is done by means of CONTOURS, which are lines cut from the earth's surface by imaginary horizontal planes at equal intervals from each other. Suppose that the territory represented by map. Fig. 8, were submerged, and later the water begins to subside by a succession of falls of the water level of 20 feet, each time leaving a deposit of silt at the water line. Even- tually the whole terrain emerges, and would appear roughly as shown in Fig. 9. The silt deposits of the various water lines would represent actual contours on the terrain itself. The whole subject of contours may be made absolutely clear by the construction of relief maps. The method which will be described is a decided departure from previous methods. Instead of the sand box, moulder's wax is used. This material lends itself admirably to this class of work, due to the fact that it is very plastic, retains its consistency, and, when the relief is completed, permits of vivid representation of all terrain features by means of indentations in the wax. In order to be successful in this work the moulder's wax must be used. Do not attempt to use the sand table. The latter answers the purpose very well for indoor work in field fortifications, but it will not do for topographical work. Every organization and military institution should secure enough of the wax for relief 36 Relief Maps 37 map construction in connection with map reading and instruction in Minor Tactics. Construction of Relief Maps The first necessity is a table constructed as shown in Fig. 7. The two enclosures on top of the table are 18" square, interior measurements (the same dimensions as the Gettysburg- Antietam 12" sheets). The flange en- closing the squares is one-fifth of an inch thick and an inch and a half in width. The top of the table should be perfectly level, and the flange of uniform thickness and planed. Also secure a rolling pin of hard wood, Fig. 7 22" long and about 4" in diameter. A suflBcient amount of moulder's wax should be secured. This may be purchased from Stewart & Company, 24 Broadway, New York City, and presumedly from other dealers. The wax comes in different colors; the olive-green is preferable for this work. The price of the wax in small orders is about twenty cents per pound, and, when ordered in large quantities, it may be secured at a reduced rate. It takes about twenty pounds to construct one of the Gettysburg- Antietam 12" sheets, but is well worth the investment. As, without doubt, you will have need to use the Gettysburg-Antietam 12" sheets in connection with studies of minor tactics, such as "Studies in Minor Tactics, 1915," and "Small Problems," etc., let us construct a relief map of one of those sheets. The necessary 12" sheets, unmounted, included in the texts 38 MiLiTAKT Sketching referred to above may be secured from the Book Depart- ment, Army Service Schools, Fort Leavenworth, at a surprisingly cheap price. The table, moulder's wax, and maps having been se- cured, the actual method of construction is as follows : Fig. 8 Place a suflScient amount of wax in each of the squares, and roll off flush with the top of the squares, so that you now have two sheets of wax each one-fifth of an inch thick. If the wax sticks to the tray and roller, apply a little talcum powder Place the map over one of the Relief Maps 39 squares, and, with a blunt stylus, trace over^the' lowest heavy contour (20 feet) on the map, leaving an impres- sion of same on the wax. Cut out that portion of the wax the surface of which, according to the map. Fia. 9 would be below the contour just traced. Take the remainder of the sheet of wax and place it upon the fease -established in the other square. Refill. the square from which the wax has just been removed, roll as before. 40 MiuTAKT Sketching and trace the next heavy contour. Continue this opera- tion, which will result in an incomplete relief map similar to that shown in Fig. 9. Fig. 10 Next, slope off abrupt surfaces between the heavy contours by moulding in small pieces of wax by hand, and the map is then completed in so far as the reUef is concerned. Next, all of the natural and artificial features of the terrain are represented by indentations in the wax. This is easily done Reuep Maps 41 by whittling out small, soft pine sticks to represent the vari- ous conventional signs, as, for example, a square end stick for buildings, a round end for trees, etc. Roads and railroads may be draw in by means of a stylus and a straight-edge. Let- ters and figures may be drawn in, or, better, stamped in with rubber stamps or steel type. Every feature is easily repre- sented, and quickly indented on the surface of the wax. When you have no further use for a particular relief map, it may be torn up and another one constructed from the same material. Fig. 10 represents the completed relief map. With the mechanical means explained above, the student is absolutely sure of constructing the relief map correctly. Hav- ing done this work, it follows automatically that he is able to read a military map. The following principles of contouring may be noted in con- nection with Fig. 9 : 1. That all points on a contour line have the same elevation above the datum plane. 2. That, where the contours are equally spaced, the slope is uniform. 3. That, where contours are straight and evenly spaced, the ground is a sloping plane. 4. That the contours of a vertical surface lie on top of one another as in palisades. 5. That, if the slope in rocky formations is over the base, then only can contours cross. 6. That every contour closes upon itself or extends entirely across the map. 7. That on water-sheds the contours are convexed toward the base of the slopes. 8. That in water courses the contours are convex toward the sources of the stream. 9. That contours far apart indicate gentle slopes. 10. That contours near together indicate steep slopes. Suggestions to Instbuctors As a knowledge of map reading goes hand in hand with the study of tactics, it is believed that a few words at this 42 MiLiTABT Sketching point regarding the co-ordination of the work would not be amiss. It has been found by the author that pleasing results with beginners may be obtained by constructing relief maps of the terrain involved in small tactical problems. Attention is invited to Sketch No. 1, page 5, "Studies in Minor Tactics, 1915." Select the 12" sheets comprised in this section; build up each sheet as above described; join the sheets together and you have the desired area for the first part of the prob- lem. Then, with the war game set, you are ready to proceed with the text. Detail two or three students each day to con- struct the area for the following day. The relief map work, after the class has been properly instructed, should be con- ducted by detail outside of the class, and eventually all will have an opportunity ' to construct a relief map without seri- ously interfering with their work or recitations. Having all of the paraphernalia necessary for the work at hand, two men should be able to construct a relief map of one of the 12" sheets in about two hours. Assuming that Part I of the text referred to will constitute part of the course: it deals with an infantry regiment that detrains, advances, reconnoiters, and attacks an enemy in position, pursues, halts for the night, establishes outposts, pre- pares and occupies a defensive position, withdraws therefrom and retreats. All of these dispositions are clearly and vividly brought before the mind of the beginner by the aid of the relief map, and gains his interest at the start. Later, when all have become more proficient in map reading and tactical disposi- tions, the ordinary map may be substituted. This is considered an important lesson, and, to obtain suc- cessful results, much depends upon the demonstrations and explanations of the instructor. LESSON VIII METHODS OF DETERMINING DIFFERENCES OF ELEVATION Prom the relief map constructed in the previous lesson, the student should now understand what contour lines are, and the necessity of placing contour lines on maps in order to form a correct idea of the locations and extent of elevations and depressions of the earth's surface. The surface of the ground is either level or sloping. As one walks along a level course, his elevation naturally remains the same, while, if he walks along a sloping course, his elevation increases or decreases according as he is going up or down hill. It has been found that the up-hill end of a line 57.3 feet long which has a slope of one degree is one foot higher than the down-hill end. Computing from these figures, we are able to determine the difference of elevation between any two points if we know the distance and the angle of slope between them. The angle of slope may be determined by various instruments especially prepared for that purpose. A very practicable method of ascertaining angles of slope is by means of the slope-board, which is inexpensive, easy of construction, and never gets out of adjustment. Construction of Slope-Board On your drawing board (see Fig. 11), construct DC per- pendicular to AB, then when a point is sighted along the straight-edge AB, the plumb line attached at D makes the same angle with the perpendicular DC that AB makes with the horizontal. This, of course, assumes that your drawing board is perfectly square. Lay off DE 5. 7S inches long on DC, then, with the radius DE describe the semicircle PEG. Lay off from E toward F and G successive distances of one-tenth inch along the arc. These divisions represent degrees, because one degree in a circle of 5.73 inches radius gives a chord of one-tenth inch. 48 44 Military Sketching Extend these degree marks to the foot of the board with a ruler as shown in Fig. 11. To read slopes, attach a plumb line at D, sight along AB at the object, keeping the board in a vertical plane. When the plumb line comes to rest, press the string against the edge of the board with the fingers and read the angle marked. Other Leveling Instruments There are several varieties of clinometers (hand instruments for reading angles of elevation) . These instruments, although more convenient than the slope-board, are rather expensive to issue to a large class, or for individuals to purchase. If purchased, full directions accompany them. Scales op Map Distances and Their Use Before taking up the subject of scales of map distances, a few terms which will be used frequently in the future will bear explanation at this point. V. I. means the vertical interval between contours. H. E. (Horizontal Equivalent) means the horizontal distance on the ground between two contours. M. D. (Map Distance) means the horizontal distance be- tween two contours on the map. A Normal System of scales has been prescribed for the U. S. Army field sketches as follows : Sketches of large areas ... 1 inch = 1 mile, V. I., 60 feet. Road sketches 3 inches = 1 mile, V. I., 20 feet. Position sketches 6 inches = 1 mile, V. I., 10 feet. Fortification sketches 12 inches = 1 mile, V. I., 5 feet. It will be seen that as the scale is increased the vertical inter- val between contours is proportionally decreased, so that by this system the M. D. is always the same for the same angle of slope whatever the scale of the map may be. The M. D. for any angle of slope may be computed from the following equation : 688XR.F.XV.I. _j^j D Angle of slope. In which 688 equals the horizontal distance in inches on a one-degree slope necessary to give a rise of one foot. Determining Differences of Elevation 45 The V. I. is expressed in terms of feet. However, its func- tion in the equation is only a relative one without regard to denomination. 20 IS 10 5 li mill nlnnliw Ke P 5 1 1 111 lin ,0 ,5 Fig. 11 If the R. F. and V. I. for any sketch made in accordance with the Normal System be substituted in the above equation, the M. D. will be the same for any particular angle. In view of this let us substitute: T> Tjl _ 1 63360' V.I. = 60. Angle of slope = 1 degree. and we have the following: 688 X 1 63360 X60 - = .65 inch X (the M. D. for one degree slope for any sketch under the Normal System). 46 MiLiTART Sketching f Dividing .65 by -» -r' -r> 1, 2, 3, 4, etc., we have the M. D. for 113 4 K 4 T 2' 4' ^' ^' ^' ^* ^^■' *1®&'"^^3 from which data a scale may be easily constructed. (See Fig. 12.) _L *. 01 0) *4 00*05 I 'I °r °i°n°i'i Fig. 12 As we have reading and working scales of distances, the same applies with elevations. Fig. 12 is a reading scale of M. D.'s (Map Distances). By applying this scale to any contoured map under the Normal System, we can readily determine the degree of slope between contours, and, by means of the table below, decide upon the practicability of military operations for the various degrees of slope. Students should be given an opportunity to study contoured maps in connection with the reading scale of M. D.'s and the table given below. The scale shown in Fig. 12 may also be used as a working scale, but a more convenient working scale will be explained later in the lesson. Degrees of slope. Operations. '2 14 to 15 Maximum for railroads. Maximum for first-class roads. Practicable for all arms. Somewhat difficult for cavalry to charge descending. Maximum for cavalry to charge in mass ascending. Infantry in close order descends with some difficulty. Cavalry can descend at a trot. Not practicable for heavily loaded vehicles. Field artillery can no longer maneuver. Maximum up to which all arms can move. Light vehicles can ascend. Foot troops can ascend or descend aided by hands. Working Scale of Elevations We have learned that a horizontal distance of 57.3 feet for 1 degree slope gives a rise of 1 foot. or 5730 feet= 100 feet rise, 5730 feet =69760 inches = 100 feet rise. Determining Differences op Elevation 47 Suppose that we are using a scale 3" = 1 mile, then 1 inch on the map equals 21120 inches on the ground. 68760H- 21120= Sjci inches on the map. Lay off a line 3J4 inches long and divide it into ten equal parts of 10 feet each, and subdivide each of the ten feet divi- sions into five equal parts of 2 feet each. Place this scale on the same ruler as your working scale of paces or strides, the left of this scale immediately below the left of your working scale of paces or strides. (See Fig. 13.) r~5iiii\ui 1(1 in (1 111(11 n (I Ml (11 11(11 H|i 1 11 |n 11(1111(1 1 ii|iiu(un|i 111(1111(1 1 11(111111111(111 1(1111(1111 |iui|un(N ^ O 2 4 6 8 10*12 1^ IS IB 30 39 ZftOO) _M Sin. = Imi. " ".PACES 7\^ O 10 20 30 40 so 60 70 80 eO 100 Fi ^ \ I I 1 I 1 I I 1 I I I I I . 1 I I I 1 I I I . I 1 I . I I 1 I 1 I 1 1 1 I . I 1 I I ■ I I I I I I 1 Fig. 13 Now suppose that you have paced a course 500 paces long with a 3-degree slope. Lay off your distance of 500 paces from your working scale of paces (the upper scale), then glance at your working scale of elevations immediately below the 500- point on the upper scale, and you have the elevation for a one- degree slope; multiply this result by three, and you have the difference in elevation between the two points considered. In a similar manner a reading scale of elevations may be con- structed under your 6-inch scale of paces or strides. This will cover two faces of your triangular working scale. On the third face should be inscribed a scale of yards for 3 and 6 inches to the mile to be used when the distances are estimated, as may frequently be the case in hasty sketching. The scale shown in Fig. 13 has been found to be much more practicable at the Army Service Schools as a working scale than the one shown in Fig. 12. Slopes may be expressed in three ways: 1. In Degrees: A one degree slope indicates that the angle between the horizontal and the given line is 1 degree. 2. In Percentages: A slope is said to be 1, 2, 3, etc., per cent when 100 horizontal units correspond to a rise of 1, 2, 3, etc., of the same vertical units. 48 MiLiTAEY Sketching 3. In Gradients: Expressed as a fraction in which the numerator represents the difference in elevation, and the denominator the horizontal distance between the two points. Degrees of slopes are used mostly in military matters, percentages for highway and railway construction purposes, and gradients for trench construction. Approximately, 1 degree slope = 1.7 per cent slope = ^ gradient. Questions fob Review 1. Explain how to construct an attachment to your drawing board for reading angles of slopes. 2. Explain vertical interval, horizontal equivalent, map distance. S. What is the Normal System of scales for use in the U. S. Army? 4. By making proper substitutions, determine the map dis- tance for 34, }/2, %, 1 up to 10 degrees of slope, and construct a scale of M. D's. for same. 5. A contoured map is given to you. From this map deter- mine the various degrees of slope, and decide upon the prac- ticability of these slopes for military operations. 6. Construct a working scale of elevations for 3" = 1 mile and 6" = 1 mile, each to read to an elevation of 100 feet. Inscribe these scales on your triangular rule as explained in this lesson. (See Fig. 13.) 7. In what three ways may slopes be expressed? Illustrate. 8. Express a 5-degree slope (a) in percentage; (6) in gradient. LESSON IX EXERCISES IN CONTOURING We should now have a very good idea of what contours are and how to determine the elevations of locations by means of our scale of elevations. Before taking up the subject of sketching, much may be learned about contouring the ground to be sketched by working out the exercises suggested in this lesson. In actual sketching, the contour lines are entirely drawn in by eye, first having given or assumed the elevation of a certain location of the ground to be sketched as a datum plane, and also having outlined the drainage by means of stream lines and elevations of certain controlling points. These controlling points are commonly called CRITICAL POINTS. Critical points, as applied to contours, are points indicating an abrupt change of elevation, as the top of a hill, or an abrupt change in the slope of the hill, also the head and foot of a ravine or water course, the junction of stream lines, etc. Having previously located on your sketch the stream lines and critical points — in other words, thoroughly outlined the drainage of the area — you should proceed to as many of these critical points as will be necessary to obtain a view of the entire area; usually two or three will prove suflScient, and you will find that from these points all of the contour lines may be drawn in by eye with a surprising degree of accuracy. Figure 14 illustrates the idea. Without even seeing the area, one is able, by means of the stream lines, dry water courses, and elevations given, to draw in the contours about as they would appear if this sketch were actually completed on the ground. In drawing in the contour lines, the student should bear in mind the principles of contouring given in Lesson VII. Each student should draw in the contours on this sketch with a soft pencil and then compare the results. This exercise will impress upon the mind the importance in sketching of first carefully outlining the drainage of the area to be sketched. 49 50 MiLiTABT Sketching Students should be given tracing paper and contoured miaps with instructions to trace upon the paper the stream lines and elevations of critical points, then remove the tracing paper from the map, and interpolate the contours, afterwards com- paring the contours interpolated with those of the original map. One may obtain a great variety of these control sketches from the Book Department, Army Service Schools. Order a complete set of them which will cost but a few cents, and then make mimeograph copies for use of the class. It will be found that, by the methods suggested above, the student will soon obtain a very accurate idea of what points are really critical in correctly contouring an area, and, when he begins to sketch, these points will stand out vividly on the terrain before him. Problem The point A, on a 3-inch map, has an elevation of 780 feet. Given the azimuth and a distance from A, and the elevation of the following points: Azimuth, Distance from A, Elevation, 'oint degrees yards feet B 20 1,000 920 C 35 500 865 D 60 800 820 E 70 300 820 F 75 1,200 920 6 90 800 840 H 110 500 785 I 115 1,000 890 J 125 700 780 K 150 400 745 L 160 1,100 700 M 180 600 780 N 200 900 845 220 400 800 P 245 1,000 895 Q 270 900 860 R 290 400 None given. s 320 800 880 T 340 300 810 U 355 900 840 Exercises in Contotjhinq 51 e7o S/O ^lace lO' CanfoUrs on ihe above shefch The fiqures qive e/ei/eih'ans in feei- FlQ. 14 52 MiMTABT Sketching A stream flows in the general direction TJ-A-K-L. A branch of this stream flows in the general direction D-K, passing mid- way between E and H. Another branch in the direction ti-A flowing for some distance in the same general direction. The latter branch has a uniform slope of one degree. From the notes given above, plot the stream lines and critical points given and interpolate the contours so as to make a pos- sible representation of the relief under the conditions given. Remember that a 3-inch map under the normal system has a V. I. of 20 feet. Note, — ^All information necessary in the solution of this problem has been given in this lesson and in the lessons preceding it. LESSON X VISIBILITY It is often necessary in military operations to determine from the map whether one point is visible from another; whether a certain line of march is concealed from the enemy; how much of a certain area can be seen from a given point; and whether slopes are uniform, concave, or convex. If the map is cor- rect, the above information may be determined very accurately, but it must be remembered that most maps have more or less minor errors in rehef so that the visibility of points, lines, and areas cannot be determined to the degree of accuracy that many may assume; also the natural and artificial objects upon the earth's surface interfere in many cases, so when there is a reasonable doubt, and if the opportunity permits, the better method would be to actually verify the visibility by visiting the'points concerned. VisiBiuTT BY Inspection By studying the relief map. Fig. 9, the following principles of visibility are obvious: (a) Contours closely spaced on the top of a hill, and grad- ually getting farther apart toward the bottom, show a con- cave slope, and all points of the intervening surface are visible from both the top and bottom of the slope. (6) Contours spaced far apart at the top and gradually closer toward the bottom show a convex slope, and neither end of the slope is visible from the other. (c) Contours equally spaced indicate a plane surface, and all intervening points are visible from top to bottom of the slope. Bearing the above principles in mind, one is often able to tell at a glance whether or not one point may be seen from another. Visibility by Pbopoetion The line of sight is determined by drawing a line from the observing point tangent to the point of probable obstruction. S3 54 MiLiTABY Sketching The visibility of any point, whether determined by proportion or graphically, depends upon the following simple proportion: Difference in Difference in Horizontal Horizontal elevation of observing point and point of obstruction. elevation of observing point and elevation necessary for point in question to be seen. distance be- tween ob- serving point and point of obstruction. distance be- tween ob- serving point and point in question. The second term of the above proportion is the unknown quantity, and will be represented by "X." Example An observing point has an elevation of 600 feet, the point of probable obstruction an elevation of 400 feet. These points are 800 yards apart. 800 yards in prolongation of this line is a hill 300 feet high. Can this hill be seen from the observing point? Following out the proportion given above we have: 200' :Z':: 800': 1600' or X= 400 feet. 600—400 = 200 feet, the necessary elevation of the point in question in order to be visible from the observing point, con- sequently the point may be seen. So it is clear that in many cases the visibility of a point may be determined by a mental calculation of the horizontal dis- tances and the difference in elevation between the observing point, and the point of obstruction. The student should assume points and distances and construct a diagram illus- trating the above proportion. By a few exercises of this nature from a contoured map, the student should be able, from inspection, to solve the more simple problems in visibility. Profile Method The more complicated problems in visibility may be readily solved by the profile method. A profile is a line supposed to be cut from the earth's surface by an imaginary vertical plane. To construct the profile, project this line to scale upon a vertical Visibility 55 plane. (See Fig. 17.) You wish to construct a profile of the line ABC. Place the lower edge of a piece of cross-section paper along the line ABC. Pick out the lowest contour lines along ABC. Naturally they are along the two streams, and both have an elevation of 500 feet. Mark dots on the lo^er edge of the paper indicating these lowest contours. Guided by the parallel and perpendicular lines of the cross- section paper, dot in the elevations of the remaining contours, allowing one horizontal space for each contour interval. Connect these dots l^y smooth curved lines, and you have the irregular line shown in Fig. 17. This is the profile of the line ABC. Then, by drawing lines of sight from the observing point tangent to the points of obstruction, the visible portions of the line ABC are determined. Visibility problems may be divided into three classes : 1. To determine whether or not one point is visible from another. 2. To determine how much of the ground line connecting the two points is visible from either point. 3. To determine how much of a certain area is visible from a given point. Visibility op a Point See Fig. 15. Let A be the observing point, B the point of probable obstruction. To determine whether the point C is visible from A. (Note that the contour interval is 20'.) As shown in Fig. 16, place the lower edge of the cross-section paper on the line ABC. Observing the points. A, B, and C, we find that A is the lowest point, B is 40 feet higher, and C is 115 feet higher than A. Let the space between the parallel lines on the cross-section paper represent one contour interval, so B will be two spaces higher than A, and C will be 5^ spaces higher than A. As .4 is the lowest of the three points, its profile position will be at the lower edge of the cross-section paper, or is identical with its map position. The profile position of B is 6, two spaces directly over B\ the profile location of C is c, 5^ spaces directly over C. Draw the line of sight from a tangent to h. It is found to pass beneath c. consequently C is visible from A. The visibility of any 56 MiUTAET Sketching point may be determined in a similar manner. If there are several points of probable obstruction, locate the profile positions of each point, and, from the point of observation, draw tangents to each profile location and, if these lines fall below the profile location of the point in question, that point is visible. Visibility of a Line Construct the profile of the Kne as previously explained. From a. Fig. 17, draw lines tangent to the points of obstruc- tion, X and b. (These are the lines of sight.) From the extremities of the visible portions of the profile, drop per- pendiculars to the line ABC, and we find, of the line ABC, that AX, YB, and ZC are visible portions. VisiBiLiTT OP Areas From the point of observation, draw several radiating hnes through the critical points of the area in question. Find the visible portions of these lines by method suggested above, and connect their extremities, and you have approximately the visible area. (See Fig. 18.) If the student is provided with a well-contoured map, some cross-section paper, and a pencil, he should be able in an hour's time, by the careful study of this lesson, to master the subject of visibility. Review Each student should be given a contoured map, and required to solve the following problems : 1. To determine the visibility of a point by observation. 2. To determine the visibility of a point by proportion. 3. To determine the visibiUty of a point by the profile method. 4. To determine the visible portion of a straight line by the profile method, the point of observation being in the same straight line. 5. To determine the visible portion of an irregular line, such as a crooked road, the point of observation being outside the irregular line. 6. To determine the visible portion of a given area. ■" " ■" ^ ^ ■■• ■" "^ ^ /^\^_^ ^^^-^ ""^nT^''^^--^ %?s>— =:r i=l " -^ "Z^ -— -Z ■ ^^^J^^s\. ::^N^^v\oO*' ^^$$^$^.?^\ ^^^:^^^^ ^ o^°5-,'°\ \ yvj )^ '^^)/JJ)/y^i'^ ^^^^yw///y^ 'x^y^/ 1 1 // /y y^ / / // / / '—^yJJ/y/ -ii^^v/V// ^^^^^V/V/ =^^^^^^^^$-^^/ x; - <:::^^-^^^<:^/ ^ mwi 0M > )> rvusrvL>rMJsrvu^^5 Fig. 29 94 MiuTART Sketching Fig. 30 LESSON XVII DELINEATIONS (Continued) Indoor Work The student having become adept in the delineations in Lesson I, will now be given a number of model sketches with instructions to copy them to the best of his ability. He should be cautioned not to hurry but to study the given sketch care- fully in order to determine the most essential features. Note the form of the skyline. Draw this in lightly after first mak- ing light pencil marks where the most marked features appear to lie. Now draw in the hues that show the ground shapes, hills and ravines, being careful to make the lines somewhat heavier as the objects get nearer until the immediate fore- ground is reached near the bottom of the sketch which may be made by using the side of the pencil point to get proper weight. An illustration of the development of the copy of a sketch is given in Fig. 31 and Fig. 32. Starting with the skyline, the sketch finally develops into a very good copy in the sixth stage at (f). In some cases it may be necessary to erase parts of the lines already made, where nearer objects interrupt or obscure them. The student should be cautioned that the essential features only, are to be represented in the sketch. In other words, things of no military value should be omitted or simply out- lined and shaded in. It is here where a well made sketch is of more importance than a landscape photograph. The camera has no sense of selection but represents the whole truth and those in the foreground most accurately and care- fully. It will, for example, picture accurately each head of wheat for a hundred yards in front of the camera, while the sunken road bed will be slurred over almost unnoticed. The sketch would here dismiss the wheat field with four lines, with probably the word "wheat" written in, and give most careful detail to the sunken road and fences at the other end of the field. Keeping the above instruction in mind, let the student 05 96 Military Sketching make sketches from such photographs as are given in Figs. 33, 35 and 36. Fig. 34 is an example of sketch covering the same ground as that shown in Fig. 33. Note the prominence of the fence and observation tower in the sketch and compare with the camera's effort. For this lesson the student should be provided with the following: 1. Pencil, Faber's HB. 2. Improvised drawing board. 3. Four thumb tacks. 4. Good grade unglazed white paper. 5. Lead pencil eraser. Delineations 97 Fig. 31 98 MiMTAHT Sketching Fig. 32 Mliiiiiii T - ^l-iiUI^ 5^^^^^^^JHH|Bj^H|^^^^^^^^^H ■HHK^^^S'i f^^^ % y^^MeiMfS^^^^iH^'feMM—iaHt "^ HltHUI "^»*/?.&»;S:^'^;£.ii>^.':%!*3.:..- __ ..... :■ ..... ..^^,_- ^. ... .1... Fig, 33 Fig. 34 Fig. 35 Fro. S6 LESSON XVIII OUTDOOR EXERCISES Explanation of Mil Scale and Improvised Aids Having completed the preliminary exercises in "Delinea- tions" the student is now ready to proceed to outdoor sketch- ing as far as making representations on paper of the objects before him. There is, however, one important phase of mili- tary sketching that must not be lost sight of. A military sketch, when completed, should be of such a nature as to be readily understood by any other person. The information portrayed on the sketch includes not only the objects them- selves, but their relative positions, not only in distance, but often of more importance is the horizontal or lateral relation. It is also convenient to have all sketches drawn to the same scale, so that these relative distances will be portrayed in- stantly to the eye without the assistance of a special scale for each individual sketch. As the Mil system of measuring angles has already been introduced to our service, the student is presumed to understand its principles. For those who may not have had instruction with Mil measurement instruments, the following explanation may be of value. One Mil is that angle whose tangent is jt^^ or in other words, it is the angle formed at the eye by two Hues that exactly subtend one yard at 1,000 yards away from the eye, or, by similar triangles, it subtends one-half yard at 500 yards. It wiU thus be seen that the Unear distance of the tangent varies in proportion to the length of the radius, although the angle remains the same. If we were to interpose a ruler ex- actly one yard in front of the eye in the above case, the tangent would be rjwj^ of a yard in length, or .036 inch. The Musketry Rule is an instrument issued by the Ord- nance Department, designed to measure Mils when held at a fixed distance from the eye. The smallest divisions indicated measure angles of 5 Mils. The actual length of this division 100 Outdoor Exercises 101 is dependent on the length of the string, which determines the distance at which it is to be held from the eye. If, therefore, we fix the distance the ruler is held from the eye to 15 inches, the angle will vary in proportion to the number of divisions we would subtend on the rule by the legs. This is the principle that is piade use of in landscape sketching for locating promi- nent features of the ground on the landscape sketch. There has been developed, at the Infantry School of Arms, what is known as the "Sketching Pad." It is a pad of speci- ally ruled paper for the convenience of the sketcher. (See Fig. 37, which represents one of the sheets on a reduced scale). In practical use, the sheet should be 83^ by 5}/2 inches. Ver- tical lines should be very light, preferably blue, or even un- inked, simply leaving a light crease. These vertical lines are of value as guides in dropping features of the landscape, located over the top of the paper, down to the sketch strip. The intercept between these vertical hues equals the 50 Mils divi- sion of the Musketry Rule. The pad should, therefore, be provided with a string so arranged through an eyelet near the center of the top, as to insure that the paper is held exactly 15 inches from the eye each time the pad is held up for orien- tation. With this length of string, the interval between the vertical lines subtends 50 Mils. The four horizontal lines drawn just below the center of the sheet should be of the same weight as the vertical lines just described. These horizontal lines are of value as guides in placing features of the land- scape located by means of the vertical edge of the pad. The highest point of the sky-line must be located somewhere on the top line of these four horizontal lines. At the top of the paper are two heavy orientation marks and three horizontal black lines defining divisions marked for the Target, Range and Deflection. At the bottom, on the left, is a place for a description of the position from which the sketch was made. In the center is a circle to contain the number of the sketch. By the side of the circle will be drawn an arrow with one barb, to show the magnetic north. On the right are spaces for the time, date, name, rank and organiza- tion of the sketcher. 10!4 MlUTABT SkETCHINCT The use of the sketching pad may perhaps be illustrated to the beginner by its analogy to a window, through which an observer is looking at a landscape. If the observer is stand- ing back from the window at a certain distance, each window pane will contain a certain section of the landscape, and the width of each pane wiU also correspond to a certain nmnber of Mils. Therefore, if the size and shape, of the window panes were altered to correspond to the section described on the sketching pad by the vertical and horizontal Hnes, it would serve as a transparent sketching pad. Now if, instead of the transparent window panes, we were to place a paper on which we could outline the landscape as seen through each pane, the result would be a landscape sketch covering the area seen through the window. The idea above expressed may be more readily understood by referring to Fig. 38. T A RN or SKETC MADE FROI- { o V ( IME_. ATE_. lAMf- lANK-C RGANI2 ATION. '■-^^ >■• Fig. 37 Various methods analogous to the window have been" im- provised to assist beginners in landscape sketching, as, for instance, the wire screen illustrated in Fig. 39. This screen Outdoor Exercises 103 could be improvised by almost any one, and by fixing the eye notch at a fixed distance perpendicular to the screen, the in- tercepts between any two wires may readily be made to cor- Fig. 38 respond to a certain fixed number of Mils. The appearance to the observer will be something like that illustrated in Fig. 40, and by having cross-section paper with the lines corre- 104 Military Sketching sponding to the screen wires, the view may very readily be transposed to paper by the sketcher. When this wire screen is used, it should, of course, be set up on a stake and remain stationary until the sketcher has completed his sketch for the area covered. In the absence of standard sketching pad blanks, the sketch may still be made to the same scale by other improvisations. Any ruler marked with uniform divisions held at a determined distance in front of the eye so that the prominent divisions will intercept a given number of Mils — ^for example, let us assume that the ruler is marked in J^ inches, and we desire that one of the divisions shall equal 25 Mils. If we remember that one Mil equals one yard at 1,000 yards, at what distance will 3^ inch equal 25 Mils? This can be determined by simply substituting values in the formula R = — jt? , which for- mula expresses the whole principle of the Mil system. In this case, W = 3^ inch, M = 25 Mils. Solving the formula with these values, R = 10 inches, therefore, if we make a cord 10 inches long, and always hold the ruler at cord's length from the eye, it will in fact be a true Mil rule. Of course, if no cord is used, the rule may be held approximately at the required distance from the eye, but it will then be only approximately correct in Mil measurement. This use is illustrated in Fig. 41. Another simple expedient that has long been in use by sketchers and painters is that of using a lead pencil, held at a uniform distance from the eye, to measure lateral distances between objects in the landscape that is being sketched. When the pencil is so used, it is usual to use the thumb as a sUding in- dicator. Examples of this use of a lead pencil are given in Figs. 42 and 43. For this lesson, the student should be provided with the following: 1. Sketch pad, with a stiff back and cord. 2. Pencil, Faber's HB. 3. Lead pencil eraser. 4. Any improvised instruments, such as screen mentioned above, and ruler for use as Mil scale. 5. Compass. Outdoor Exercises 105 FiG.r39 Fig. 40 106 Military .Training Pig. 42 OUTDOOB^EXBRCISES 107 Fig. 43 LESSON XIX SUB-SKETCH Up to the present, the student has been concerned only with the making of the sketch proper. It may often happfen that the scale of the sketch does not permit certain objects to be shown in sufficient detail. To draw the whole sketch to larger scale would entail unnecessary time and labor. It is, therefore, found convenient to draw a sub-sketch of very important features. The method shown in Fig. 41 is self-explanatory. The field glasses should be used for such sketching. In conjunction with road sketching, it is frequently of ut- most military importance to show the appearance of the land- scape from given points on the road, even though such features will actually be beyond the limit of the road sketch itself. This method is illustrated in Fig. 45. Usually, these sub- sketches are made to a standard scale, though somethnes it is permissible to exaggerate the vertical dimensions slightly. The sub-sketches made in conjunction with the road sketch are usually made by an assistant, numbers being placed at points on the road to correspond with the numbers placed on the sub-sketch. However, if there is no assistant for this purpose, the sketches may be placed on the road sketch paper itself, as illustrated in Fig. 45, lines being drawn to represent the approximate angle subtended by the view. Usually these views are made to include important features on the road itself, such as bridges, and cuts or fills. The student should equip himself the same as in Lesson III. 108 Sub-Sketch 109 Fig. 44 ROAD SKETCH NEAR UANGFORD BRIDGE June 16,1916 By 1st. Lieut. F.B.SMITH.IOth.lnf. Scale 3" = I mile le* o seo looo le* o si= M.D. V.I. 20' Fig. 45 LESSON XX RANGE DATA The student should now be required to complete sketches on the standard sketch pad in the manner shown in Fig. 46, that is, all important military features should be shown, not only on the sketch itself, but a line should be drawn vertically from the sketch itself till it intersects the three horizontal lines near the top, and on this line should be written in the proper place, the target, the range to that target, and the deflection to that target from a given reference point. In all cases, the reference point will be similarly indicated with a zero deflection. Care should always be taken that the name of the place from which the sketch was made is not omitted from the lower left hand corner and that the single barbed arrow, giving the magnetic north, appears near the circle at the center. The number near the cii'cle should always indicate the relative position of sketches from enemy right to enemy left. The range should, when practicable, be measured with a standard range finder. Frequently, when the principal thing needed is the military information of the sketch, the sketch itself may be omitted for the purpose of saving time, and direction lines only are then drawn from the small circle towards the targets. At an approximate distance (sometimes, but not always measured to scale), is drawn a quick sketch representing the target only, or sometimes only an X is placed on the line and a word written, such as " ford," " tree," etc., near this mark. An exampile of this case is given in Fig. 47, which represents what is called the range card, for the same ground given in Fig. 46. It is thus seen that a range card is a simplified landscape sketch which does not require any pictorial ability on the part of the sketcher. The necessary fire data are placed on the upper left-hand corner of the range card ia the place provided on the blank. The deflection, however, is given near the top, and is measured in • Mils from the reference point. The range is also frequently written along the direction line toward any target. Th« 111 112 Military Sketching targets are also numbered from enemy right to enemy left, and the firing data for each target are recorded in the space provided. The illustration given in Fig. 47 is that of a ma- chine-gun range card. These cards are made out for each individual gun, and the number in the circle may be supple- mented by such additional data as the particular case may require, for example, "No. 1 Gun, Company A, 335 M. G. Bat." The machine-gun range card remains at the position of the gun when the machine-gun crew is relieved. The sketch given in Fig. 48 is another illustration showing how firing data are expressed on a landscape sketch. Though it is deskable that all sketches should be uniform in appearance, the only essential feature that must be adhered to is that the firing data must be expressed directly above the target and near the top of the sketch. Ford T'aJ'-ro/ F/afrop Trench 'Tord RN n Tr'anae: 7f/yae # / Giyn iftour& Patp 4-:oo7?M. /Yo*/. /<7^ /y/y Name /-nf i>n dT . (5 f/ s i/ej Rank & Organ, y^a/ror Jr7fo/7/'ry Fig. 47 114 Military Sketching should already be computed and entered before opening fire, but that data should be changed after delivering fire so as to show the actual data determined by fire. The space below the six horizontal lines and above the body of the sketch is used for noting the angular distances from the reference point to prominent points on targets shown. These angles should be recorded immediately below the lower of the six horizontal lines. Other data pertaining to targets, notes, reference to sub-sketches, etc., may also be placed in this space. The sketch proper is usually confined below the top dim horizontal line, in the same manner as in the sketch previously discussed. The space below the sketch proper should have the same nota- tion as the previous sketches discussed, adding condition of the weather, which is needed in calculating artillery data, and of course such other miscellaneous notations as may be necessary in any particular case. The student should equip himself the same as in Lesson III. Place :^ 3pv)yitjdale. S<^^oo/ House Fig. 48 WEATHER- Cleekrr NAME- J. C. Wt'/hMMf, Syir Range Data 115 ^-'So Place: Hex for e( DATE- \ ■Sept' 17 t-\OVFrX"'PH NVEATHER- Clear- NAME- V/ir A/icAey. JL* It- Fig. 49 APPENDIX SUGGESTIONS FOR INSTRUCTION AT TRAINING CAMPS The author has had considerable experience in instruction pertaining to this subject at training camps, and the following suggestions may prove of some value to those upon whom this duty may fall in the future. With the intensified course of training pursued at training camps, the time usually allotted to this subject is very limited, possibly not more than a half dozen periods of two hours each, so that it is a foregone conclusion that the instructor must work against time throughout the course. Another handicap is the limited number of instructors proportionate to those imdergoing instruction, but, regardless of these serious disad- vantages, much may be accomplished if the right methods are pursued. Let us first consider the necessary preparations to be made by the instructor previous to the first instruction period. Aside from the authorized text-book, the student will require the following articles: 1. Drawing board with slope board attachment. 2. Compass. 3. Triangular ruler. 4. PencU, Faber's HB. 5. Eraser. 6. Four thumb tacks. 7. Drawing paper. Drawing Board With large classes it is obvious that it would not be practi- cable to provide Engineer drawing boards. The tripod, al- though a convenience for the beginner, is not essential. The following plan proved successful at the Plattsburg Training Camps of 1915: purchase a suflScient amount of soft pine material 12" by 1" and saw into boards about a foot square. The drawing board may be suspended around the neck by 116 Suggestions for Instruction at Training Camps 117 means of a strong cord attached to the sides of- the board in such a manner as to hold it in a horizontal position at the proper height for sketching. Compass Write to the Keuffel & Esser Cmpany, or any other reliable dealer, for samples, and select some good round compass that may be set into the drawing board by means of boring a hole of the same diameter as the compass, and of a sufficient depth to make the top of the compass flush with the surface of the board. By purchasing the compasses in lot, a considerable reduction may be obtained. Attachment for Reading Slopes With the many duties incident to training camp life, the men will not have the time nor the paraphernalia for construc- ing the slope board attachment. These should be placed on the boards before the camp begins. (See Fig. 11.) The process is simple, and with the aid of a few trained enlisted men, the work can soon be accomplished. Triangular Ruler Go to some plaining mill and secure a sufficient number of triangular rulers similar to one shown in Fig. 2. Only the plain triangular pieces 6 inches long need be obtained. Pencils, Erasers, Thumb Tacks, and Paper These articles should all be secured in advance by the camp exchange officer. The Faber HB penfcil is recommended, or any other pencil of about the same degree of hardness. As to the paper, transparent sheets may be obtained at a reasonable rate. This class of paper is of advantage as the rain will not affect it to any great extent, and prints may be made directly from the field sketches; however, for instruction purposes, the ordinary sheets of drawing paper will answer the purpose. Do not fail to have the equipment as outlined ready for issue at the first period of instruction or previous to that time. The cost of the entire equipment as given above will not amount to 118 Military Sketching much. The compass will be the largest item, but, as a matter of fact, it is a very essential part of a soldier's equipment. Pos- sibly, funds allotted for training camp purposes may be avail- able, especially for the drawing boards and the labor in con- nection with the attachment for reading angles of slope. Do not attempt to have several work at the same drawing board. The plan has not proven successful. One or two will do the work and the remaining men will accomplish little. Each must do the work individually. FiBST Pebiod This period may be employed as follows : Having assembled the class a conference may be held involving the principles outlined in Lessons I and II, also pointing out the necessity of being able to make a sketch and read a military map. Then take the entire class to the target range, if one is available; if not, then to some suitable course previously measured, and let each man determine the length of his pace or stride as described in Lesson I. When this has been done, without doubt the time allotted will have been used up, and the class mat be dismissed with instructions to inscribe on their tri- angular ruler, aided by Figs. 2 and 3, a working scale of paces or strides for 3" equals one mile and 6" equals one mile. The following text references for the second period should also be given out : Lessons VI and XL There will probably be very little time for any preparation, but those who do find a few minutes to read over the text references for the following day will be in a more receptive mood to grasp the practical work. , Second Period Explain by the aid of the blackboard the following basic principles of sketching: orientation, distance, direction, inter- section, resection, and conventional signs. Students may consult the text freely regarding the latter until they become familiar with the various signs. Then assign some short, irregular course, not over a mile and a half in length, and, if practicable, a closed course. With a large class it will be found better to divide the class into sections, appointing such Suggestions fob Instruction at Training Camps 119 assistants as you may have in charge of the various sections, and prescribing several courses. Many members of the camp will be found to be experienced engineers, although not familiar with the hasty sketching methods followed out in the army. Such men should be distributed among the various sections, as they naturally acquire a knowledge of the work more readily and will render valuable assistance in helping the less fortunate over difficulties. Third Period Relief Map and Contours Before the opening of the camp, secure a sufficient amount of moulder's wax and construct a relief map similar to the one shown in Fig. 9, exhibiting the original map along with the relief map. These maps may be displayed in a vertical and elevated position at the conference, and the nature and object of contours explained therefrom. Following this explanation, mimeographed copies of Fig. 14 or some similar illustration should be issued to the class, and each member should be required to interpolate the contours. In other words, impress on the student's mind the importance of first outlining the drainage. An explanation of the auxiliary scale of elevations shown in Fig. 13 and its use should be given. Each man should place this scale for 3" and 6" equals one mile on his triangular work- ing scale. Fig. 13 is a correct scale of elevations for 3" equals one mile. By using every other division, a scale of elevations for 6" equals one mile may be constructed. Also explain the use of the slope-board. This entire period is devoted to conference. Text reference for following period: read over Lesson XII. Fourth Period Road Sketch Pick out about one and a half miles of road, preferably with as much relief as possible. If practicable, select several routes so that the roads will not be too congested with sketchers. Text reference for following period : read over Lesson XIII. 120 Military Sketching Fifth Period Position and Outpost Sketch Select several areas of about half of a square mile, and assign sections to their tasks, first explaining basic principles as outlined in Lesson XIII. Text reference for following period : read over Lesson XIV. Sixth Period Place Sketch Deploy the entire class along some crest, and require each to sketch a prescribed sector, first explaining basic principles as outlined in Lesson XIV. It was found at the Plattsburg Training Camps that, after a course of six periods as outlined above, nearly gvery man was able to turn in very creditable road, position, and place sketches. Their idea of drainage was good, and, along with the practical work, they had automatically learned much about reading a military map.