Equipment for map revision 
  
The aforementioned equipment series also covers the field of map revision. Since it is 
here mainly a question of graphical plotting, the instruments primarily developed for this purpose - 
Planicart and Planitop - should be used. A few characteristics of these instruments are particu- 
larly valuable for this type of work. They will be discussed in the following. In addition, certain 
practical work will be mentioned in connection with the different instruments. 
Planicart 
1.- Internal tracing table - As has been mentioned before, one of the most important design fea- 
tures of the Planicart is its internal tracing table which is of the luminous type. The latter is par- 
ticularly important for scribing, a technique frequently used in map revision. 
  
The internal tracing table will be modified in the next manufacturing series. The surface for 
the tracing sheet (not the model range) has been slightly changed. It now measures 1.00 m x 1.10 m. 
Slots are provided at the sides of the tracing surface which allow overhanging parts of the manus- 
cript to project into the free space below the instrument orthe manuscript can be rolled into holders. 
The following operations of map revision be performed very economically on the internal tra- 
cing table : 
- Determining changes by comparing map and air photo in the instrument. 
- Partial orientation of model to remaining features. 
- Complete or partial plotting of new detail on the map sheet. 
- Graphical orientation of plot to unchanged features as well as cartographic treatment and com- 
pletion. ; 
2.- Model range - In the Planicart, as in the Planimat, single-arm guide rods are used. In other 
words, the image cardan is located between the perspective center and the space point of the model. 
This ensures a very wide range of magnification from air photo to model. For super-wide-angle 
photography, this range is 1.5 to 3.5 x and for wide-angle photography 1.3 to 3, 5 x. These wide 
ranges leave great freedom for selection of the model scale. The high magnification also allows 
larger scales such as 1:10 000 or 1:5 000 to be directly revised on the internal tracing table. 
Secondary enlargement of the model on an external tracing table is, of course, likewise pos- 
sible. In this case, an electrically connected coordinatograph with transmission by synchros is 
used. Maximum magnification from model to map is 8 x. 
3. - Guiding the floating mark - In the Planicart, the floating mark is guided via spindles by means 
of handwheels or a pedal disk. For freehanded guiding, the terrain carriage can be separately 
disengaged in the x and y-coordinates. 
  
4.- Viewing - The Planicart features right angle viewing with a stationary optical system. This 
ensures high viewing quality. In conjunction with 6 x eyepiece magnification, this viewing system 
reduces difficulties of identification to a minimum even in small-scale photography (1:50 000 and 
smaller). 
The map sheet itself is viewed through a wide-field magnifier. 
5. - Tracing device - Tracing tools for all types of plotting are available in the Planicart : pencil 
ball pen, ink-pen holder, pricking pin and sapphire pin for scribing. 
Planitop 
The main features which make the Planicart an ideal instrument for map revision also 
apply to the Planitop. This is a mechanical-projection instrument with a focal-length range from 
normal to ultra-wide angle and an internal tracing table. In addition, there are the following special 
features for plotting at topographic scales : 
1. - Model range - The Planitop has two-arm guide rods. In other words, the perspective center 
is located between the image cardan and the space point of the model. As a result, the magnifica- 
tion range is very favorably located for the operator. This design also allows lesser magnifica- 
tions, such as are needed for small-scale work at about 1:25 000 or 1:50 000. The magnification 
range is 0.5 to 1. 4 x for wide-angle and 0. 8 to 1. 5 x for super-wide-angle photography. The model 
can be further enlarged on an external tracing table. In this case, a straight two-arm pantograph 
is used giving enlargements of 6 x model to map.