91 
3. MAKING THE ANAGLYPH MAP 
Such stereo-map is possible to be observed in all its 
original colours but only with stereoscope. Smaller 
part can be observed with special viewing methods 
(parallel view method, cross-eye view method). 
Merging of two stereo-pairs is possible, if they are 
represented as an anaglyph. This method was first 
used in 1858 from Spaniard d'Almeida. Later on 
Rollman has introduced a method for projection of 
diapositives of the stereogram, which was 
successfully used by Louis Lumière in his stereo 
cinema projection (additive anaglyph method). 
3.1 Anaglyph Method 
The anaglyph method uses colour to encode the 
right and left image pairs. This method requires a 
wear of special glasses with colour filters over each 
eye. Best results we get, if used filters are of 
complementary colours. International Stereoscopic 
Union has chosen the red filter on left and the blue, 
cyan or green filter on right for standard disposal. It 
is also in coordination with the red used in 
international marking of ships, planes and 
politicians. 
3.2 Anaglyph Types 
The anaglyph image could be encode in three 
different ways: colour (colour anaglyph), gray (gray 
anaglyph*) and pure (pure anaglyph). 
The pure anaglyph method converts the original 
into a pure red/blue or red/green image 
(depending on the type of glasses you have) - 
with empty green or blue channel in RGB mode. 
This method gives the best 3D effect, but 
sacrifices the colour data and image intensity. 
Gray anaglyph as same as pure anaglyph 
represents the image but in grayscale version of 
the original image coloured in red and blue or 
green. Althought the colour information is not 
preserved, this type of an anaglyph is most 
common, because it is typically easier to view. 
Colour anaglyph uses red and yellow colour for 
the left stereopair and ussualy cyan for the right 
stereopair of the image. Colour anaglyph tries to 
preserve as much of the original image colour 
as possible. Not all images are suitable for a 
colour anaglyphs. Using of yellow colour allows 
us to present the image in colours. All colours 
can not be seen by observing an image with 
special glasses. 
Because of that, to present our map as colour 
anaglyph, we should carefully choose the colours for 
cartographical elements. With mixing the different 
values cyan, red and yellow and using the red/blue 
glasses a 3D impression of the map can be 
achieved in wanted colour tints. Pure red or cyan 
can not be used. 
3.3 Making the Anaglyph 
If we want to present a stereo-map as an anaglyph, 
both stereopairs should be merged. The easiest way 
to do it, is by help of computer: 
1. Rasterise both stereo-pairs and present it in RGB 
mode; 
2. Delete the red channel (contents) from the image 
of right stereo-pair; 
3. Copy the red channel from the image of left 
stereo-pair; 
4. Paste the red channel of the left image into red 
channel of the right image. 
The result is an anaglyph map. Because of the RGB 
mode this map could be observed with special 
glasses only on the computer screen or projected 
with datascope to the screen. 
Figure 4: The anaglyph map 
3.4 Reproduction the Anaglyph 
Teoreticaly we could print the anaglyph map with 
transformation of the image into CMYK mode. In 
practice is better to print the anaglyph map in three 
colours (red, green-blue and yellow for colour 
anaglyph), because anaglyphs are very delicate on