10 
only be used, when supplementary details which are not 
visible from the air, such as culverts, subterranean 
drainage etc. are added. A sample of such an inventory 
map is shown in Appendix 3. 
The orthophoto inventory map has the advantage that 
nearly all details of the highway, such as traffic signs, 
road markings, guard rails, barriers, maintenance areas, 
parking lots etc. may be interpreted directly without 
special auxiliary means and if necessary may be supple- 
mented with descriptive data. An important feature of 
these photomaps for highway maintenance is the drawn-in 
boundary between the road property area and the neigh- 
bouring parcels. Further the control points used for 
the final photogrammetric cadastral survey may be re- 
corded in the orthophotomap. It would lead too far to 
describe here the methods of photogrammetric surveys 
for the established right-of-way and new property boun- 
daries, as practiced in Germany today, using the mani- 
fold possibilities of electronic data processing for 
improvement of the planimetric accuracy. Reference is 
made to the publications concerning these procedures 
(Ref. ' 5,9). 
In connection with the production of inventory maps as 
orthophotomaps various secondary purposes can be satis- 
fied, e.g. checking the correct execution of the project 
according to design and the determination of sections 
where the erection of screens against oncoming headlights 
is necessary. Also the limitation of sight distances by 
vegetation, fences, slopes etc. is easier to check on 
the orthophotomap than on line maps.