phase cartographique (VII-1) et de recherche d'instruments simples permettant à la fois une bonne 
identification, une mise en place par coincidence de la carte et de l'image photographique, et un 
tracé facile (par exemple IV-3). 
Conclusion 
Actuellement, nous n'avons pas de doctrime définie en matière de révision et il serait 
souhaitable de poursuivre certains essais pour mieux codifier certaines méthodes afin de les trans- 
former en éléments d'un processus régulier. Mais, de toutes façons, la variété des problèmes 
posés par les feuilles à réviser, en fonction du relief, de la quantité d'éléments à réviser et des 
particularités propres à l'histoire de la feuille (homogénéité, révisions successives) fait qu'il 
conviendra d'étudier chaque cas particulier afin de choisir la meilleure méthode. 
Abstract 
For the revision of our basic map 1:25 000, we take aerial photographs at scale 1:30000. In a hilly terrain, new 
details are plotted by a Poivilliers type D. When the terrain may be shared in plane facets, local rectification of a single 
photograph is used : a "Stereoreviser' gives a stereo view of a facet of the adapted photograph and of the other photo- 
graph of the stereo pair. 
A revision manuscript is drawn and completed on the field. Then it is used for scribing the corrections on the 
original printing plates. 
We have two problems : how to adapt our plotting to the existing map (so we prefer the "photo-on-map' technicsy 
to have stereo view during the topographic interpretation. 
We are testing a method using orthophotographs. We have rapidly tested the stereo-orthophotographic method 
which is depicted by M. Van Wijk in a appendix. 
Appendix 
STEREO-ORTHOPHOTOGRAPHY AND MAP REVISION 
M.C. VAN WIJK 
National Research Council of Canada, 
Ottawa. 
The orthophoto possesses certain potential in map revision as a result of the fact that it 
can be produced rapidly to offer practically up-to-date terrain information. The geometrical qua- 
lity of orthophotos simplifies map revision to the point that required changes only need be traced 
from the orthophoto image and incorporated into the map. 
One of the difficulties in using orthophotos is that certain information to be updated may 
be difficult to interpret on a single orthophoto image without the aid of stereoscopic viewing. Map- 
ping of features such as buildings may not be sufficiently accurate from a single orthophoto because 
of displacements in the orthophoto image of details located above ground elevation. Also changes 
in the terrain height, for example resulting from construction cannot be interpreted and recorded. 
It seems therefore that stereoscopic interpretation of the orthophoto image combined with 
derivation of height information is essential in a map updating system based on the use of orthophotos. 
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