FIGURE 1. Ground shot in "La Selva", Costa Rica. 
The lines in the field, identified by targets and transferred onto medium-scale 
photography were not difficult to find from the air. Both lines were overflown 
repeatedly as the characteristics of the radar altimeter were varied. Slight deviations 
from the line were not supposed to be critical because the strip surveyed in the field was 
120 m wide. 
Analysis of data 
The principal point of each 70 mm photograph obtained concurrently with the 
radar profiles (Figure 2) was plotted on mosaics prepared from 230 mm photography. 
This gave the radar's ground track which was then transferred onto the contour maps 
from which the "true" ground profile was determined. This profile as well as the radar 
profiles recorded on a strip chart were digitized and machine processed (Figures 3 and 4). 
To evaluate the tree canopy profile a photogrammetric profile of line ] was 
made by joining together a strip of seven stereo models of 230 mm format panchromatic 
aerial photographs obtained during the radar altimeter trials. The scale of the photos