5. Photographic overlap 
The need for stereo coverage depends on the ability to identify vegeta- 
tive forms, variability on ground cover, and stress characteristics on 
the photography. Frequently, recognition characteristics of cropland 
were adequate to recognize monoscopically (20 percent for coverage). 
Range shrubs, plants and forest types usually require stereoscopic 
interpretation for accurate delineation. 
RESULTS 
Quality of Classification 
  
Examination of the Goose Lake data revealed two sources of errors in the 
original classification which could be attributed to errors in ‘'ground- 
truth" data. These errors included pixels which were properly grouped 
(clustered), but not adequately or correctly described; and pixels which 
were incorrectly clustered. 
Statistical accuracy of this original classification varied from about 50 
percent to 90 percent. Reclassification of the selected plots revealed 
the two sources of errors. The revised classification was not applied to 
the complete study area, so a comparison of accuracy levels was not pos- 
sible. This will be closely followed on the Five-County Study. 
The improved classification was possible because individual pixels were 
located on the photos and on-the-ground. The location of individual 
pixels or pixel groups is made possible by transfer procedures described 
next. 
Data Transfer System 
  
Comparison of classification efforts on the Goose Lake project indicate 
that classifications based upon ground-truth data enhanced by low flight 
CIR photography resulted in correction of class descriptions and proper 
clustering of many pixels which were in error on the original classifica- 
tion.