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CADASTRE ET LEVÉS AUX GRANDES ÉCHELLES 
THE USE OF ORTHOPHOTOS FOR FOREST INVENTORY 
AND THE AUTOMATIC DRAWING OF FOREST MAPS 
R. KERSTING 
Mainz (Fed. Rep. of Germany) 
Introduction 
It is the acknowledged object of forestry to work out a plan for a sustained management. 
This plan has to be based on facts which are supplied by an inventory. To apply these facts 
easily maps are used to illustrate prospectively the data. 
In Germany a new inventory is made every 10 years. From this data, a new revised 
working plan is made. Before orthophotography was introduced in forest mapping, the maps 
were compiled from cadastral maps, which showed mostly only the boundaries. The forest 
situations such as roads, forest sections, landscaping, etc.. was surveyed from ground level. 
Later on aerial photographs and rectified mosaics were used to fill in the forest situation. But 
because of the vast mountainous regions of forest found in Germany, this procedure, although a 
great help, did not solve the problem satisfactorily. 
In 1971 a new situation arose : The forest administration of the Federal State of 
Rheinland- Pfalz was assigned in addition to her own states forests, the inventory and planning of 
the community forests. Because of this addition a yearly inventory has to be made over 60 000 ha. 
To master this new problem, new methods had to be introduced in forest inventory gathering 
data to produce effective forest maps. This situation was aggravated even more because the state 
of fundamental data and maps used by the community forests is rather poor compared to those of 
the state forests. 
At about this time the photogrammetric and data processing department of the state 
reallotment administration which is equipped with 3 stereoplanigraphs C8, including storage 
units SG 1, and 1 orthoprojector GZ 1 with a reading unit had ample capacity to produce 
orthophotos. So now we could start to introduce orthophotography into forest inventory and 
mapping. 
Orthophotography 
To meet the needs of the forest administration with a limited plotting capacity we had 
to choose a rather small photo scale of 1:33 000 to begin with. The photos are taken with a wide 
angle camera of 15/23 cm on panchromatic or infrared material depending on the season. From 
a model scale of 1:20 000 we produce orthophotos of 1:10 000 which later on are enlarged to 
1:5 000. In addition to our work for the reallotment department, we scan about 300 models a 
year at a rate of two models a day in one shift. 
The orthophotos have been a great success in forest inventory work. Without this new 
method the additional inventory of the community forests could not have been mastered with the 
limited personal on hand. The orthophoto combines in an ideal way the advantages of an aerial 
photo with those of an accurate map. It serves the forest surveyor defining and valuating the 
different sections of woods for a working sheet in the field. Because it is true to scale any 
boundary, once defined on the photo is surveyed at the same time. 
After completion in the field jt forms the base for producing or updating the forest maps. 
It makes it further possible to compute the area of the different sections before the final map is 
completed so that this data for the forest management plan may be compiled when still drawing 
the map. 
Last but not least the orthophoto, is used as a photo map in addition to a line map or as 
a sole forest map. 
This is not the time to elaborate on the advantages and disadvantages of a photo map 
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