we have some cds with digitized old army maps (called RETM, some should be from NATO sources) - it consist of many seamless tiles - many TIFF files and TFW files defining the coordinates:
2.11506 0.0 0.0 -2.11506 420000 5500000
I searched in the documentation and found this (translated with Google):
(hope, that I removed all typos and illogical translations)
Codename segment files are created as follows:
t - codename RETM
pp - indicates 6 ° UTM meridian strip
xxxx - code coordinate N (North), in relation to the lower left corner of the segment
the marking coordinate system in which the segment was created (there are always w for the northern hemisphere)
yyy code to coordinate E (East), in relation to the lower left corner of the segment
Codename (t) type RETM is as follows:
f RETM 25 ("25" means 1 : 25 000 scale)
e RETM 50
d RETM 100
Marking 6 ° meridian strip (pp) consists of two digits of the band. Zones are numbered from 1 to 60th. Czech Republic is located in the 33rd and 34th zone.
Code for coordinate N, respectively. E (UTM) bottom left corner of the segment is designed so that the plane rectangular coordinates of a corner in meters divided by the actual size of the segment in meters (the RE scale 1: 100 000 by 10 000, RE 1: 50 000 number 5 000, RE 1: 25 000 number 2 500, etc.). If the result coordinates fewer characters, make up the left with zeros.
For example, for segment 50 in the 33rd RETM zone coordinates of the left lower corner:
x = 5 500 000
y = 500 000
5 500 000 / 5 000 = 1100
500 000 / 5 000 = 100
Name of the segment e331100w100.tif
Name e331100w100.tfw text file and the file contains six rows with values:
4.23012 pixel size in meters in the x-axis
0.0 Rotation in row
0.0 Rotation in column
4.23012 pixel size in meters in the y-axis
500,000 E-coordinates of upper left corner
5550000 N-coordinates of upper left corner
The segments are organized into zones. Zone means a coherent set of segments, covering an area of a 6 ° meridian strip. This space is extended to the east and west for an additional two full segments to overlap between adjacent zones is at least two segments.
I have problem with converting this to something with normal coordinates like X = 14,xxxxxx; Y = 50,xxxxxx common in our country and I did not find any way yet, how to recalculate the coordinates to get "normal" ones.
Manual georeferencing in QGis or SAGA works OK, but it distorts the image (while it should be already projected) and comparison of coordinates from RETM maps and Google maps (which I used for manual georeferencing) does not show any solution.
I would be grateful If someone could give me an advice.