1

For some reason, a vendor found it convenient to move from a Gauss–Krüger coordinate system (EPSG:31466) to something like WGS84 but then multiplied by one million. Hence lon = 6090805, lat = 50777584, should become 6.090805, 50.777584. Is there already a proj4 definition to transform this "coordinate system"? If not, could anyone help with a projection string?

  • If the units were defined as microdegrees the Esri WKT string would become UNIT[“Microdegree”,0.000000017453292519943295]. Not sure what proj4 would require – Vince Dec 12 '19 at 11:32
2

The answer by Gabriel de Luca is a good suggestion. However, the goal is to divide, not multiply, the coordinates with 1000000:

Proj 4.9.3:

> echo 6090805 50777584 | cs2cs -f %.6f +proj=eqc +R=57295779.5130823209 +to +proj=lonlat 
> 6.090805 50.777584 0.000000

Other options with later releases of Proj:

Using cct instead of cs2cs and the unit conversion that was introduced in Proj 5.0.0:

> echo 6090805 50777584 |  cct -d 6 -t 0 -z 0 +proj=pipeline +step +proj=unitconvert +xy_in=1 +xy_out=1000000 
> 6.090805 50.777584 0.000000 0.0000

Using cs2cs with the noop and affine projection options that are available since Proj 6.1.0:

> echo 6090805 50777584 | cs2cs -f %.6f +proj=noop +to +proj=affine +s11=.000001 +s22=.000001
> 6.090805  50.777584 0.000000
1

You could use the never well weighted Equidistant Cylindrical projection:

If you want a circumference of 360000000, you must use a radius of (C/2*PI=) 57295779.5130823209...

Ok, let's see:

C:\>cs2cs +to "+proj=eqc +R=57295779.5130823209"
90 90
90000000.00     90000000.00 0.00
30 60
30000000.00     60000000.00 0.00
180 1
180000000.00    1000000.00 0.00
10 10
10000000.00     10000000.00 0.00
45 45
45000000.00     45000000.00 0.00
90 45
90000000.00     45000000.00 0.00
180 90
180000000.00    90000000.00 0.00
-180 90
-180000000.00   90000000.00 0.00
181 90
-179000000.00   90000000.00 0.00
360 45
0.00    45000000.00 0.00  
  • Any hint? cs2cs +to "+proj=eqc +R=57295779.5130823209" Using to definition: proj=eqc +R=57295779.5130823209 Rel. 4.9.2, 08 September 2015 <cs2cs>: projection initialization failure cause: unknown projection id program abnormally terminated – Skinkie Dec 12 '19 at 15:00
  • proj Rel 6.2.1 here – Gabriel De Luca Dec 12 '19 at 15:06
  • I made a typo with egc vs eqc. But it doesn't work with proj 4.x. – Skinkie Dec 12 '19 at 15:09
  • In this topic of OSGeo mailing list the alias in proj4 seems to be eqd. – Gabriel De Luca Dec 12 '19 at 15:42

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