EMPLOYMENT OF BALLOONS.

In view of the above, the work most suitable for balloons is as follows:

GENERAL SURVEYANCE OF ENEMY’S ACTIVITIES.

(a) Reporting modifications of enemy defensive organization; detecting movements of convoys and trains. Their importance and itineraries, locating infantry signals, and all other activities such as revealed by fires, smokes, dust, trails, etc.

(b) Spotting active hostile batteries and reporting hostile shelling. Reporting hostile shelling is a duty for which balloons are especially suitable, as they are favorably situated to observe both the flash of the gun and the fall of the shell. From this information it is possible to direct not only neutralizing fire on the hostile battery, but often also to establish the caliber of the guns and the arc of fire of the battery.

RANGING AND ADJUSTING OF FIRE.

(a) Observing fire for destruction on all targets, counterbattery, or bombardment.

(b) Reporting fleeting targets and observing fire on them.

(d) Observing fire on the enemy’s communications.

(e) Cooperation with aeroplanes.

PART II.
WORK IN THE BASKET.

[Translation of French document, “Instructions au sujet du Travail en Nacelle,” a publication of French G. Q. G., 1918, by Lieut. Kellogg.]

The rapidity and precision of the work in the basket depend not only on the natural gifts of the observer, but also very largely on his methods of work.

The object of the following instructions is to tell the student observers the general methods they should follow and to explain the use of these methods.

The principal operations which they must be able to execute rapidly are as follows:

1. Orientation and general reconnaissance of the terrain.

2. Spotting points on the ground seen on the map and points on the map seen on the ground.

3. Observation of fire.

Chapter 1.
ORIENTATION AND GENERAL RECONNAISSANCE OF THE TERRAIN.

This is the operation which the observer executes on his first ascension in a new sector; this is how it should be conducted.

1. Rapidly look over the terrain around the ascensional point in order to orient the map.

This is done by finding in some direction from the ascensional point a line giving an easily identified direction (a road, an edge of woods, etc.). Orient the map so as to make this line on the map parallel to the line on the ground.

The map can also be oriented by means of the compass.

2. Locate the horizontal projection of the balloon.

The observer may know already the winch position, but the balloon is carried off horizontally from the winch sometimes as much as 400 or 500 meters (436 to 545 yards). Thus it is essential not to confuse the winch position with the horizontal projection of the balloon. If this is done, errors will be made in the operations which we are going to discuss later, where we make use of this known point.

It is pretty hard to materialize definitely the vertical line passing through the basket. The effect of the wind and the movements of the balloon make it impossible to use a plumb line. The observer has to find his projection on the ground by leaning first from one side of the basket and then from the other in order to diminish the chances of error. An approximation of 25 or 50 meters is sufficiently accurate for the general reconnaissance which it is necessary to make.

3. Leaving the region beneath the balloon, acquaint yourself, step by step, with the most prominent points in different directions—masses of woods, villages, etc.

There are two methods—by the process of cheminement or tracing landmarks and by the process of direct alignment.

The process of “cheminement” or tracing consists in following outlines, such as roads, streams, or hedges, identifying as you go along details of the terrain which these lines pass through or near. On account of the deformations due to the effect of perspective and to the unevenness of the ground, and particularly on account of the deformation of angles, if it is a winding road, this method often leads to errors; it should be employed only in certain cases defined below:

The process of “direct alignment” consists of studying the terrain by following successive directions from the balloon position.

We call the “alignment” of a point the trace, on the terrain, of the vertical plane passing through this point and through the eye of the observer; in perspective vision, when the observer determines the point in question, this alignment would appear to him a vertical line. On the map it is nothing more than the straight line joining the point under consideration to the vertical projection of the balloon.

The method of alignment, then, consists in first identifying the most prominent points near the balloon and finding, by cheminement or tracing, the lines running from these points. A point found directly by cheminement should not be considered as definitely determined until its alignment has been verified.

This first reconnaissance is not to study the terrain in all its details, but only to fix in the memory a certain number of prominent points scattered throughout the sector in order to facilitate later work.

These points should be very distinct, visible to the naked eye, and of characteristic forms, so that there will be no danger of confusing them with others—masses of woods, important villages, etc. Roads with borders of trees, large paths for hauling supplies, when taken together, are very valuable for quickly finding others.

Chapter II.
SPOTTING OF POINTS.

Generalities.—In all spotting operations, whether working from the map to the terrain or vice versa, the difficulty is due to the fact that the situation of the point has to be found on a two-dimension surface.

The best method of work will be, then, that which suppresses as quickly as possible one of these dimensions and to conduct the research on a straight line.

Any point can be placed on the terrain or on the map if you know the following elements:

1. Its “direction” or alignment.

2. Its situation on this alignment—that is, its “range.”

In oblique vision, a digression in direction is always much more apparent than a digression of the same size in range. Thus the direction of a point can be identified with more facility and precision than its range. For these reasons, the following methods consider two distinct phases in all spotting operations:

1. Investigation of direction.

2. Investigation of range.

The investigation in direction always comes first, as it is easier, and its result makes the investigation for range easier.