Application of Orthophotomaps in Highway Work 
  
by W. Blaschke, Münster 
An orthophoto is an aerial photograph of the earth's 
surface. The scale and planimetric accuracy of an ortho- 
photo correspond so closely to an orthogonal projection 
that no relevant deviations may be noticed. 
An aerial photograph contains all information of the 
terrain and the objects visible from above. This is also 
valid for the orthophoto where this information can be 
located in plan to graphical accuracy. If the orthophoto 
contains contour lines and slope symbols this location 
can be done in height too. 
The orthophotomap differs from a conventional map in 
  
so far as the terrain is represented by an orthophoto. 
The cartographic additions to the orthophotomap can be 
limited to those details which cannot be recognized 
or interpreted in the orthophoto. The application of 
orthophotomaps is of particular interest in highway 
work, as all details visible from the air and important 
to highway design, construction or maintenance may be 
interpreted without the need for special modes of gene- 
ralisation.