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.
CHAPTER II
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.)
[1878]. A military sketch is a rough map showing the features of the ground that are of military value.
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.