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.