  MAP READING AND MILITARY SKETCHING
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The following additional points about contours should be remembered:
(a) A Water Shed or Spur, along with rain water divides, flowing away from it on both sides, is indicated by the higher contours bulging out toward the lower ones (F-H, Fig. 6).
(b) A Water Course or Valley, along which rain falling on both sides of it joins in one stream, is indicated by the lower contours curving in toward the higher ones (M-N, Fig. 6).
(c) The contours of different heights which unite and become a single line, represent a vertical cliff (K, Fig. 6).
(d) Two contours which cross each other represent an overhanging cliff.
(e) A closed contour without another contour in it, represents either in elevation or a depression, depending on whether its reference number is greater or smaller than that of the outer contour. A hilltop is shown when the closed contour is higher than the contour next to it; a depression is shown when the closed contour is lower than the one next to it.
If the student will first examine the drainage system, as shown by the courses of the streams on the map, he can readily locate all the val
For example: On the Elementary Map, Woods Creek flows north and York Creek flows south. They rise very close to each other, and the ground between the points at which they rise must be higher ground, sloping north on one side and south on the other, as the streams flow north and south, respectively (see the ridge running west from Twin Hills).
The course of Sandy Creek indicates a long valley, extending almost the entire length of the map. Meadow Creek follows another valley, and Deep Run another. When these streams happen to join other streams, the valleys must open into each other.
| Slope (degrees) | Rise (feet) | Horizontal Distance (inches) |
|---|---|---|
| 1 deg. | 1 | 688 |
| 2 deg. | 1 | 688/2 = 344 |
| 3 deg. | 1 | 688/3 = 229 |
| 4 deg. | 1 | 688/4 = 172 |
| 5 deg. | 1 | 688/5 = 138 |
It is a fact that 688 inches horizontally on a 1 degree slope gives a vertical rise of one foot; 1376 inches, two feet, 2064 inches, three feet, etc., from which we see that on a slope of 1 degree, 688 inches multiplied by vertical rises of 1 foot, 2 feet, 3 feet, etc., gives us the corresponding horizontal distance in inches. For example, if the contour interval (Vertical Interval, V. I.) of a map is 10 feet, then 688 inches × 10 equals 6880 inches, gives the horizontal ground distance corresponding to a rise
Let us assume the R. F. to be 1/15840—that is to say, 15,840 inches on the ground equals 1 inch on the map, consequently, 6880 inches on the ground equals 6880/15840, equals .44 inch on the map. And in the case of 2 degrees, 3 degrees, etc., we would have:
M. D. for 2° = 6880/15840 × 2 = .22 inch;
M. D. for 3° = 6880/15840 × 3 = .15 inch, etc.
From the above, we have this rule:
To construct a scale of M. D. for a map, multiply 688 by the contour interval (in feet) and the R. F. of the map, and divide the results by 1, 2, 3, 4, etc., and then lay off these distances as shown in Fig. 11, Par. 1867a.
FORMULA
M. D. (inches) = 688 × V. I. (feet) × R. F./Degrees (1, 2, 3, 4, etc.)
The left-hand division is marked 1/2°; the next division (one-half as long) 1°; the next division (one-half the length of the 1° division) 2°, and so on. The 1/2° division means that where adjacent contours on the map are just that distance apart, the ground has a slope of 1/2 a degree between these two contours, and slopes up toward the contour with the higher reference number; a space between adjacent contours equal to the 1° space shown on the scale means a 1° slope, and so on.
What is a slope of 1°? By a slope of 1° we mean that the surface of the ground makes an angle of 1° with the horizontal (a level surface. See Fig. 10, Par. 1867). The student should find out the slope of some hill or street and thus get a concrete idea of what the different degrees of slope mean. A road having a 5° slope is very steep.
By means of this scale of M. D.'s on the map, the map reader can determine the slope of any portion of the ground represented, that is, as steep as 1/2° or steeper. Ground having a slope of less than 1/2° is practically level.
1st. A one degree slope means that the angle between the horizontal and the given line is 1 degree (1°). See Fig. 10, Par. 1867.
3d. A slope is said to be one on one (1/1), two on three, (2/3), etc., when one unit horizontal corresponds to 1 vertical; three horizontal correspond to two vertical, etc. The numerator usually refers to the vertical distance, and the denominator to the horizontal distance.
Degrees of slope are usually used in military matters; percentages are often used for roads, almost always of railroads; gradients are used of steep slopes, and usually of dimensions of trenches.
- 60 degrees or 7/4 inaccessible for infantry;
- 45 degrees or 1/1 difficult for infantry;
- 30 degrees or 4/7 inaccessible for cavalry;
- 15 degrees or 1/4 inaccessible for artillery;
- 5 degrees or 1/12 accessible for wagons.
The normal system of scales prescribed for U. S. Army field sketches is as follows: For road sketches, 3 inches = 1 mile, vertical
They are pointing in the direction that is north on the map. The arrow with a full barb points toward the north pole (the True North Pole) of the earth, and is called the True Meridian.
The arrow with but half a barb points toward what is known as the Magnetic Pole of the earth, and is called the Magnetic Meridian.
The Magnetic Pole is a point up in the arctic regions, near the geographical or True North Pole, which, on account of its magnetic qualities, attracts one end of all compass needles and causes them to point towards it, and as it is near the True North Pole, this serves to indicate the direction of north to a person using a compass.
Of course, the angle which the Magnetic needle makes with the True Meridian (called the Magnetic Declination) varies at different points on the earth. In some places it points east of the True Meridian and in others it points west of it.
It is important to know this relation because maps usually show the True Meridian and an observer is generally supplied with a magnetic compass. Fig. 15 shows the usual type of Box Compass. It has 4 cardinal points, N, E, S and W marked, as well as a circle graduated in degrees from zero to 360°, clockwise around the circle. To read the magnetic angle (called magnetic azimuth) of any point from the observer's position the north point of the compass circle is pointed toward the object and the angle indicated by the north end of the needle is read.
You now know from the meridians, for example, in going from York to Oxford (see Elementary Map) that you travel north; from Boling to Salem you must travel south; going from Salem to York requires you to
Having once discovered the direction of north on the ground, you can go to any point shown on your map without other assistance. If you stand at York, facing north and refer to your map, you need no guide to tell you that Salem lies directly to your right; Oxford straight in front of you; Boling in a direction about halfway between the directions of Salem and Oxford, and so on.
The scale of the map enables us to determine the distance; the contours, the height; and the time meridian, the direction.
Thus (see map in pocket at back of book), Pope Hill (sm') is 800 yards from Grant Hill (um') (using graphical scale), and it is 30 feet higher than Grant Hill, since it is on contour 870 and Grant Hill is on contour 840; Pope Hill is also due north of Grant Hill, that is, the north and south line through Grant Hill passes through Pope Hill. Therefore, the position of Pope Hill is fully determined with respect to Grant Hill.
Orientation
Methods of Orienting a Map
1st. By magnetic needle: If the map has a magnetic meridian marked on it as is on the Leavenworth map (in pocket at back of book), place the sighting line, a-b, of the compass (Fig. 15) on the magnetic meridian of the map and move the map around horizontally until the north end of the needle points toward the north of its circle, whereupon the map is oriented. If there is a true meridian on the map, but not a magnetic meridian, one may be constructed as follows, if the magnetic declination is known:
(Figure 16): Place the true meridian of the map directly under the magnetic needle of the compass and then move the compass box until
2d. If neither the magnetic nor the true meridian is on the map, but the observer's position on the ground is known: Move the map horizontally until the direction of some definite point on the ground is the same as its direction on the map; the map is then oriented. For example, suppose you are standing on the ground at 8, q k' (Fort Leaven worth Map), and can see the U. S. penitentiary off to the south. Hold the map in front of you and face toward the U. S. penitentiary, moving the map until the line joining 8 and the U. S. penitentiary (on the map) lies in the same direction as the line joining those two points on the ground. The map is now oriented.
Having learned to orient a map and to locate his position on the map, one should then practice moving over the ground and at the same time keeping his map oriented and noting each ground feature on the map as it is passed. This practice is of the greatest value in learning to read a map accurately and to estimate distances, directions and slopes correctly.
True Meridian
The line joining the "pointers" of the Great Bear or Dipper, prolonged about five times its length passes nearly through the North Star, which can be recognized by its brilliancy.
For example, the roads on the Elementary Map can be easily distinguished. They are represented by parallel lines (======). The student should be able to trace out the route of the Valley Pike, the Chester Pike, the County Road, and the direct road from Salem to Boling.
Private or farm lanes, and unimproved roads are represented by broken lines (= = = =). Such a road or lane can be seen running from the Barton farm to the Chester Pike. Another lane runs from the Mills farm to the same Pike. The small crossmarks on the road lines indicate barbed wire fences; the round circles indicate smooth wire; the small, connected ovals (as shown around the cemetery) indicate stone walls, and the zigzag lines (as shown one mile south of Boling) represent wooden fences.
Near the center of the map, by the Chester Pike, is an orchard. The small circles, regularly placed, give the idea of trees planted in regular rows. Each circle does not indicate a tree, but the area covered by the small circles does indicate accurately the area covered by the orchard on the ground.
Just southwest of Boling a large woods (Boling Woods) is shown. Other clumps of woods, of varying extent, are indicated on the map.
The course of Sandy Creek can be readily traced, and the arrows placed along it, indicate the direction in which it flows. Its steep banks are indicated by successive dashes, termed hachures. A few trees are shown strung along its banks. Baker's Pond receives its water from the little creek which rises in the small clump of timber just south of
A railroad is shown running southeast from Oxford to Salem. The hachures, unconnected at their outer extremities, indicate the fills or embankments over which the track runs. Notice the fills or embankments on which the railroad runs just northwest of Salem; near the crossing of Sandy Creek; north of Baker's Pond; and where it approaches the outskirts of Oxford. The hachures, connected along their outer extremities, represent the cut through which the railroad passes. There is only one railroad cut shown on the Elementary Map—about one-quarter of a mile northeast of Baker's Pond—where it cuts through the northern extremity of the long range of hills, starting just east of York. The wagon roads pass through numerous cuts—west of Twin Hills, northern end of Sandy Ridge, southeastern end of Long Ridge, and so on. The small T's along the railroad and some of the wagon roads, indicate telegraph or telephone lines.
The conventional sign for a bridge is shown where the railroad crosses Sandy Creek on a trestle. Other bridges are shown at the points the wagon roads cross this creek. Houses or buildings are shown in Oxford, Salem, York and Boling. They are also shown in the case of a number of farms represented—Barton farm, Wells farm, Mason's, Brown's, Baker's and others. The houses shown in solid black are substantial structures of brick or stone; the buildings indicated by rectangular outlines are "out buildings," barns, sheds, etc.
Plates I and II give the Conventional Signs used on military maps and they should be thoroughly learned.
In hasty sketching, in order to save time, instead of using the regulation Conventional Signs, very often simply the outline of the object, such as a wood, a vineyard, a lake, etc., is indicated, with the name of the object written within the outline, thus:
Such means are used very frequently in rapid sketching, on account of the time that they save.
Visibility
On account of the necessary inaccuracy of all maps it is impossible to determine exactly how much ground is visible from any given point—that is, if a correct reading of the map shows a certain point to be just barely visible, then it would be unsafe to say positively that on the ground this point could be seen or could not be seen. It is, however, of great importance for one to be able to determine at a glance, within about one contour interval, whether or not such and such a point is visible; or whether a given road is generally visible to a certain scout, etc. For this reason no effort is made to give an exact mathematical solution of problems in visibility further than would be useful in practical work with a map in the solution of map problems in patrolling.
In the solution of visibility problems, it is necessary that one should thoroughly understand the meaning of profiles and their construction. A profile is the line supposed to be cut from the surface of the earth by an imaginary vertical (up and down) plane. (See Fig. 21.) The representation of this line to scale on a sheet of paper is also called a profile. Figure 21 shows a profile on the line D—y (Figure 20) in which the horizontal scale is the same as that of the map (Figure 20) and the vertical scale is 1 inch = 40 feet. It is customary to draw a profile with a greater vertical than horizontal scale in order to make the slopes on the profile appear to the eye as they exist on the ground. Consequently, always note especially the vertical scale in examining any profile; the horizontal scale is usually that of the map from which the profile is taken.
A profile is constructed as follows: (Fig. 21): Draw a line D'—y' equal in length to D—y on the map. Lay off on this line from D' distances equal to the distances of the successive contours from D on the map. At each of these contour points erect a perpendicular equal to the elevation of this particular contour, as shown by the vertical scale (960, 940, 920, etc.) on the left. Join successively these verticals by a smooth curve, which is the required profile. Cross section paper with lines printed
The above method of determining visibility by means of a profile is valuable practice for learning slopes of ground, and the forms of the ground corresponding to different contour spacings.
Visibility of Areas
This method is a rapid approximation of the solution shown in the profile. In general it will not be practicable to determine the visibility of a point by this method closer than to say the line of sight pierces the ground between two adjoining contours.
MILITARY SKETCHING
(While this chapter presents the principal features of military sketching in a simple, clear manner, attention is invited to the fact that the only way that any one who has never done any sketching can follow properly the statements made, is to do so with the instruments and the sketching material mentioned at hand. In fact, the only way to learn how to sketch is to sketch.)
Military sketching is the art of making such a military sketch.
Military sketches are of three kinds:
- Position sketches, Fig. 1;
- Outpost sketches;
- Road sketches.
All kinds of military sketches are intended to give a military commander detailed information of the ground to be operated over, when this is not given by the existing maps, or when there are no maps of the area.
The general methods of sketching are:
(1) The location of points by intersection.
(2) The location of points by resection.
(a) From the known or assumed elevation of a located station as A, Fig. 1 Y, (elevation 890), the elevations of all hill tops, stream junctures, stream sources, etc, are determined.
(b) Having found the elevations of these critical points the contours are put in by spacing them so as to show the slope of the ground along each line such as (a)-(b), (a)-(c), etc., Fig. 1 Y, as these slopes actually are on the ground.
To find the elevation of any point, say C (shown on sketch as c), proceed as follows:
Read the vertical angle with slope board, Fig. 2, or with a clinometer, Fig. 4. Suppose this is found to be 2 degrees; lay the scale of M. D.
The above is the entire principle of contouring in making sketches and if thoroughly learned by careful repetition under different conditions, will enable the student to soon be able to carry the contours with the horizontal locations.
In a particular locality that is to be sketched there is generally some point the elevation of which is known. These points may be bench marks of a survey, elevation of a railroad station above sea level, etc. By using such points as the reference point for contours the proper elevations above sea level will be shown.
In case no point of known elevation is at hand the elevation of some point will have to be assumed and the contours referred to it.
If the sketcher desires he may omit determining the slopes of the stream lines and instead determine the elevations of a number of critical points (points where the slope changes) in the area and then draw in the contours remembering that contours bulge downward on slopes and upward on streams lines and ravines.
If time permits both the slopes of the stream lines and the elevation of the critical points may be determined and the resulting sketch will gain in accuracy.
Figs. 5, 6, 7, 8, and 9 show these methods of determining and sketching in contours.
Road sketches and extended positions; scale 3 inches to a mile, vertical (or contour) interval, 20 feet.
Position or outpost sketches; scale 6 inches to a mile, vertical (or contour) interval, 10 feet.
This uniform system is a great help in sketching as a given map distance, Par. 1867a, represents the same degree of slope for both the 3 inch to the mile or the 6 inch to the mile scale. The map distances once learned can be applied to a map of either scale and this is of great value in sketching.
Construction of Working Scales
In going up and down slopes one's pace varies. On level ground careful pacing will give you distances correct to within 3% or less.
The following tables give length of pace on slopes of 5 degrees to 30 degrees, corresponding to a normal pace on a level of 30.4 inches:
| Slopes | 0° | 5° | 10° | 15° | 20° | 25° | 30° |
|---|---|---|---|---|---|---|---|
| Length of step ascending | 30.4 | 27.6 | 24.4 | 22.1 | 19.7 | 17.8 | 15.0 |
| Length of step descending | 30.4 | 29.2 | 28.3 | 27.6 | 26.4 | 23.6 | 19.7 |
For the same person, the length of step decreases as he becomes tired. To overcome this, ascertain the length of pace when fresh and when tired and use the first scale in the morning and the latter in the afternoon.
The result of the shortening of the pace due to fatigue or going over a slope, is to make the map larger than it should be for a given scale. This is apparent when we consider that we take more paces in covering a given distance than we would were it on a horizontal plane and we were taking our normal pace.
In going up or down a slope of 3 or 4 we actually walk 5 units, but cover only 4 in a horizontal direction. Therefore, we must make allowance when pacing slopes.
In practice it has been found that the scale of strides is far more satisfactory than a scale of paces.
1st method. The so-called "One thousand unit rule" method is as follows:
Multiply the R. F. (representative fraction) by the number of inches in the unit of measure multiplied by 1000; the result will be the length of line in inches necessary to show 1000 units.
For example, let us suppose that we desire a graphic scale showing 1000 yards, the scale of the map being 3 inches equal 1 mile:
Multiply 1/21120 (R. F.) by 36 (36 inches in 1 yard, the unit of measure) by 1000,—that is,
(1/21120) × 36 × 1000 = 36000/21120 = 1.7046 inches.
Therefore, a line or graphic scale 1.7 inches in length will represent 1000 yards.
If we desire a working scale of paces at 3 inches to the mile, and we have determined that our pace is 31 inches long, we would have (1/21120) × 31 × 1000 = 31000/21120 = 1.467 inches.
We can now lay off this distance and divide it into ten equal parts, and each will give us a 100-pace division.
2nd method. Lay off 100 yards; ascertain how many of your paces are necessary to cover this distance; multiply R. F. by 7,200,000, and divide by the number of paces you take in going 100 yards. The result will be the length of line in inches which will show 2000 of your paces.
3rd method. Construct a scale of convenient length, about 6 inches, as described in Par. 1863, to read in the units you intend to measure your distance with (your stride, pace, stride of a horse, etc.), to the scale on which you intend to make your sketch.
For example, suppose your stride is 66 inches long (33 inch pace) and you wish to make a sketch on a scale of 3 inches = 1 mile. The R. F. of this scale is 3 inches/1 mile = 3 inches/63360 inches = 1/21120. That is 1 inch on your sketch is to represent 21120 inches on the ground. As you intend to measure your ground distances by counting your strides of 66 inches length, 1 inch on the sketch will represent as many of your strides on the ground as 66 is contained into 21120 = 320 strides. For convenience in sketching you wish to make your scale about 6 inches long. Since 1
- Drawing board with attached compass (Fig. 2);
- Loose ruler, on board (Fig. 2);
- Rough tripod or camera tripod;
- Scale of M. D.'s (shown on ruler, Fig. 2);
- Scale of sketchers, strides or paces (at six inches to one mile), on ruler;
- Clinometer (not necessary if board has slope board, Fig. 6);
- Scale of hundreds of yards shown on ruler;
- Scale of paces.
Methods to be used
(1) Select a base line,—that is, a central line 1/4 to 1/2 mile long in the area to be sketched. It should have at its ends some plainly marked objects, such as telegraph poles, trees, corners of buildings, etc., and from its ends, and intermediate points, a good view of the area should be possible. The base line selected should be capable of being measured.
(2) Set up, level and orient the drawing board at one end of the base (A), Fig. 1, Y, for example. Draw a meridian on the sheet parallel to the position of the magnetic needle. Assume a point (A), Fig. 1, Y, corresponding to the ground point (A), 890, on the sheet, in such a position that the area to be sketched will lie on the sheet.
(3) Sight at hilltops, stream junctures, stream heads, etc., to begin the locations of these points by intersection, labelling each ray so as to be able to identify it later.
(4) Traverse to (b) and complete the locations by intersection as previously explained. If the base line is not accurately measured, the map will be correct within itself in all of its proportions, but its scale will not necessarily be the scale desired.
(5) Draw the details of the country between A and B and in the vicinity of this line, using the conventional signs for roads, houses, etc.
(6) The lines from station (b), Fig. 1, X, to any of the other located points may now be used as a new base line to carry the work over additional area.
(7) In case parts of the area are not visible from a base line, these parts are located by traversing as before explained.
(8) Having learned by several repetitions the above steps, the sketcher will then combine contouring with his horizontal locations.
- Drawing board or sketching case;
- Loose ruler;
- Scale of strides, or paces, if made dismounted; scale of time trotting or walking, if mounted;
- Scale of hundreds of yards, at three inches to 1 mile;
- Scale of M. D.'s;
- Slope board (if clinometer is not available).
Methods to be used
(1) At station 1, Fig. 10, orient the board as described in par. 1872, holding the board in the hands, in front of the body of the sketcher, who faces toward station 2.
(2) Important points in the vicinity, such as the railroad bridge, the stream juncture, hilltops, are sighted for intersections, lines drawn as shown and the sketcher traverses to station 2.
(3) At station 2 he locates and draws in all details between station 1 and 2, to include about 300 yards on each side of the road.
(4) The traverse is then continued forward as described for 1 and 2.
(5) After some practice of horizontal sketching, as just described,
(6) When the traverse runs off the paper as at A, Fig. 10, the following method is followed: Reorient the board so that the road forward will lie across the long dimensions of the paper; draw a meridian parallel to the compass needle and assume a point on the new sheet corresponding to the last point (A) plotted on the first sheet.
(7) On completion of the sketch various sections will be pasted together, so that all the meridians are parallel.
A logical step would be to carefully plot the line a' b', and then the lines c' c" and c" d.
If the area is densely wooded we run "line of level" by using the slope board or clinometer and by taking elevations at points arbitrarily selected. Our lines will look something like this:
Each party will be given its rectangle with the traverses sketched in. They will each then run similar traverses over the other two sides of their area and then fill in. In this manner the whole work is tied up to the original lines.
Another method
The line A B, Fig. 12, is carefully plotted. Each of the four sketching parties has two sketching groups. One group of party No. 1 traverses line a' Y; then the other group of the party traverses the line a" y'. The first group of party of No. 2 accompanies them. The second group of party No. 2 traverses the line c" d, accompanied by the first group of party No. 3; the second group of party No. 3, and the first group of party No. 4 traverse b" z', and the second group of party No. 4 traverses b' Z. When the first group of party No. 1 arrives at Y, it traverses Y y'. The second group of party No. 1, arriving at y', cuts the sheet along traverse and gives the first group of party No. 2 the part which shows their area; and then traverses toward Y from y'. Upon meeting the first group of party No. 1, they join forces and proceed to fill in their area.
In the same manner areas W X a' b' are filled in.
The method described above is useful in working over country which is densely wooded, and in which a general view cannot be obtained, for example, in mapping jungles.
An additional article of the sketcher's equipment is a holder for his pencils, alidade, eraser, knife, pins, etc. This consists of a series of small pockets sewed on to a piece of canvas about 7 inches by 4 inches. This can be attached to the left breast of the sketcher's coat or shirt by means of two pins. In addition to keeping all of his implements in a handy place the holder prevents the loss of the several articles. Nothing is so discouraging to the sketcher as to look for his pencil, eraser, knife or even alidade and find that he has left it several hundred yards back where he sat down last to sketch in details. By using the holder the sketcher gets into the habit of replacing articles after they are used and consequently always has them with him when needed. These holders ready made can be obtained from the Secretary, Army Service Schools at Fort Leavenworth, Kansas.
In sketching a good quality of paper should always be used as erasures will be frequent. A specially prepared paper that has the appearance of oiled paper can be obtained commercially and is excellent for sketching in damp weather. It has considerable resistance to rain. Sheets of celluloid prepared for sketching are invaluable in sketching in the rain. These are a part of the equipment of the case of sketching instruments supplied battalions in the regular army. These sheets may be procured at most any dealers.
Points for Beginners to Remember
2. Use hard pencils when learning to sketch—4H to 6H—and go over your work afterwards with a softer pencil—2H.
3. Do not try to put down on your sketch a mass of small details that are too small to be shown on the scale at which you are sketching. For example, if you are making a sketch on a scale of 3 inches = 1 mile, do not try to show each house in a row of houses; simply indicate that there is a row of houses, by putting down several distinct conventional signs for houses in a row; nor should you try to show every little "cut" through which the road may run. Only use about one sign to the inch of telegraph or telephone lines, for wire fences, etc.
4. When first practicing sketching only plot the route over which you walk, indicating it by a single line. When you can do this with facility, go back over one of these plotted routes and fill in the woods, houses, streams and the other large features.
5. The beginner should sketch the same ground several times over—at least three or four times. Practice alone will make perfect.
6. Always try to compare your finished sketch with an accurate map of the ground, if one is obtainable. Try to practice on ground of which you can obtain a map.
7. Make each course (the distance you go between points where the direction of your route changes) as long as possible.
8. Do not try to contour until you are expert at making a sketch showing all the flat details (roads, streams, woods, houses, etc.).
9. Never try to "sketch in" the contours until you have plotted the stream lines or the direction of the valleys, ravines, etc. The contours are fitted to or sketched around the drainage system; not the drainage system to the contours.
10. Always "size up" ground before you sketch it; that is, take a general view of it, noticing the drainage system (the direction in which the streams flow or ravines run), the prominent hills and ridges, the direction the roads run, etc.
11. Above all things, DON'T FAKE ANY PART OF YOUR MAP.
If the man using your map happens to strike the faked portion, he immediately condemns your whole map as incorrect. Every other part may be highly accurate, but your whole map is discredited because the user strikes the bad part first. You will naturally put little faith in the man who has told you something you know to be untrue. You will always suspect him. So it is with maps. Don't put down anything that you don't know to be correct. If any guess work is to be done, let the man using the map do it,—he knows that he is guessing and will be governed accordingly, but if you do the guessing, he doesn't know where the guessing begins and the accurate work leaves off. Don't fudge. Your name is on the map,—don't have any questionable work hitched up to your name.
