[Proj] Using EPSG codes with cs2cs

Tue May 8 02:55:11 PDT 2012

Amro wrote:

> PROJCS["DHDN / Germany zone 4",
> ...
> ... PARAMETER["central_meridian",12], ...
> ...
> EPSG=31495

That's not consistent. Zone 4 is indeed the one with central meridian 12,
but as Jose wrote, the EPSG code should be one of

> epsg: 31464    # DHDN / 3-degree Gauss zone 4 (deprecated)
> epsg: 31468    # DHDN / 3-degree Gauss-Kruger zone 4

However, strangely enough, there is a third, semi-possible code

epsg: 31494   "DHDN / Germany zone 4" (deleted)

but note that it should end with 94, not 95, for zone 4.

More generally, to handle EPSG codes 31491 to 31495, you must turn the 9 upside down!
But this is not an old typo. The codes with 9s used to be the EPSG codes for the German
zones, but they were deprecated in the olden days when EPSG had the unfortunate habit
of deleting erroneous entries from the database. (This was the practice before July 2001;
see http://www.epsg.org/guides/docs/G7-1.pdf , footnote on p. 33).

I think the reason at the time for deprecating/deleting them, was only to change the
names, replacing "Germany" by "3-degree Gauss".  Possibly also to correct the grammar
error in the datum name (your WKT has Deutsche instead of Deutsches in the datum
name).

But ESRI continued to support the deleted codes ( http://support.esri.de/files/support/FAQs.pdf ),
so you can still see them used, even though they are no longer in the EPSG database.
They are not supported by Proj.4 or listed on spatialreference.org. Hm, I wonder if supporting
them could be a violation of EPSG Terms of Use, paragraph 6.7:

> 6.7. No data that has been modified other than as permitted in these Terms of Use shall be attributed to the EPSG Dataset.

Anyway, in 2001, the EPSG codes 31461 to 31465 were deprecated, too. Code 31461, zone 1,
was deprecated because "ProjCRS zone not used", and wasn't replaced until much later.
Codes 31462 to 31465, zones 2 to 5, were deprecated because "ProjCRS related to
inappropriate Coordinate system resulting in incorrect axes and name", and replaced
with EPSG codes 31466 to 31469.
    (The deprecated entries were assigned the axes Easting (X) and Northing (Y)
in that order, so they are right-handed systems. The corrected entries have the axes
Northing (X) and Easting (Y) in that order, so they are left handed systems, and X goes north.)

Poor little zone 1 wasn't rehabilitated until July 2011, when epsg:5520 was added,
which is also as a left-handed system with Northing (X) followed by Easting (Y).

Finally, early in 2012, new right-handed variants of all these systems were reintroduced
(EPSG Change Request 2011.104), but the new ones are not yet in Proj.4 or spatialreference.org.
In the new right-handed variants, the axes are abbreviated E and N instead of X and Y.

epsg:5676   "DHDN / 3-degree Gauss-Kruger zone 2 (E-N)"
epsg:5677   "DHDN / 3-degree Gauss-Kruger zone 3 (E-N)"
epsg:5678   "DHDN / 3-degree Gauss-Kruger zone 4 (E-N)"
epsg:5679   "DHDN / 3-degree Gauss-Kruger zone 5 (E-N)"
epsg:5680   "DHDN / 3-degree Gauss-Kruger zone 1 (E-N)"

Best regards,

Mikael Rittri
Carmenta
Sweden
http://www.carmenta.com

________________________________
From: proj-bounces at lists.maptools.org [mailto:proj-bounces at lists.maptools.org] On Behalf Of Jose Gonçalves
Sent: den 7 maj 2012 15:21
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Using EPSG codes with cs2cs

Hi

Are you sure of EPSG code 31495? In my epsg file, installed with proj, I can find only:

epsg: 31461    # DHDN / 3-degree Gauss zone 1 (deprecated)
epsg: 31462    # DHDN / 3-degree Gauss zone 2 (deprecated)
epsg: 31463    # DHDN / 3-degree Gauss zone 3 (deprecated)
epsg: 31464    # DHDN / 3-degree Gauss zone 4 (deprecated)
epsg: 31465    # DHDN / 3-degree Gauss zone 5 (deprecated)
epsg: 5520      # DHDN / 3-degree Gauss-Kruger zone 1
epsg: 31466    # DHDN / 3-degree Gauss-Kruger zone 2
epsg: 31467    # DHDN / 3-degree Gauss-Kruger zone 3
epsg: 31468    # DHDN / 3-degree Gauss-Kruger zone 4
epsg: 31469    # DHDN / 3-degree Gauss-Kruger zone 5

If a projection ID is not in the file the expected answer is the one you got. It is not a configuration problem.
Check http://spatialreference.org to check the epsg code

Regards

Jose Gonçalves

2012/5/7 rps_rt <ec_eng01 at yahoo.com<mailto:ec_eng01 at yahoo.com>>
Dear Warmerdam and all members,

I have been browsing and reading for a while to convert my coordinates with
no hope until finding this Proj. 4.

Kindly, I seek your support here ... I am using Linux Ubuntu to convert from
long/lat (WGS84) to Cartesian (x/y) and vice versa. My need here is to get
as accurate as possible results (cm-level if possible).

I was reading this thread because I had a problem of getting a cs2cs results
for espg=31495, while I could get them for espg=31468. But the conversion
results with the later one were not accurate ~ almost 100 meters away.

e.g.,: echo "13.755944 51.054555" | cs2cs +init=epsg:4326 +to
+init=epsg:31468

but when I change it to: echo "13.755944 51.054555" | cs2cs +init=epsg:4326
+to +init=epsg:31495,
I get the message "projection initialization failure cause: no options found
in 'init' file".

I tried to change something based on this thread, to make sure that my
PROJ_LIB path is in place, but it seems I ruined everything. Afterwards, all
espg zones gave the below error:
"
pj_open_lib(epsg): call fopen(/usr/local/bin/cs2cs/epsg) - failed
Using from definition: init=epsg:31467
Rel. 4.8.0, 6 March 2012
<cs2cs>:
projection initialization cause: no system list, errno: 20
"

I tried to "make uninstall" and "make install" but nothing was fixed!!

Here are more details about my project:

My locations are in Dresden city, Germany, (DHDN4), and I have (I assume)
all what is needed to get my coordinates converted accurately, but no idea
how to process them in Proj. 4 (I am totally new here):

PROJCS["DHDN / Germany zone
4",GEOGCS["DHDN",DATUM["Deutsche_Hauptdreiecksnetz",
SPHEROID["Bessel 1841",6377397.155,299.1528128]],PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",12],
PARAMETER["scale_factor",1],PARAMETER["false_easting",4500000],
PARAMETER["false_northing",0],UNIT["metre",1]]
TOWGS84=582.0,105.0,414.0,5.042e-6,1.696e-6,-1.4932e-5,8.3
EPSG=31495

%Seven parameters:
% 582.00     - Translation dx in meter to WGS84
% 105.0      - Translation dy in meter to WGS84
% 414.50     - Translation dz in meter to WGS84
% 5.042e-6   - Rotation ro (omega) in Radiant to WGS84
% 1.696e-6   - Rotation rf (phi) in radiant to WGS84
% -1.4932e-5 - Rotation rk (Kappa) in Radiant to WGS84
% 8.3e-06    - Mapscale factor in ppm (parts per million) to WGS84(m)

Sorry for the long thread but did not want to miss any details, even in my
first ever thread in this forum.

I will be looking forward to reading form you.
Best regards,
Amro

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