[Proj] Using EPSG codes with cs2cs

Wed May 9 05:32:05 PDT 2012

PS.

Amro,
speaking about grid shift files: Dresden is in Saxony, right? I had a vague recollection
of other German grid shift files, and I have now managed to find one for you: the grid
shift file for Saxony, SAETA2010.gsb, which you can get from here

     http://www.landesvermessung.sachsen.de/inhalt/etrs/etrs.html

Follow the link to "Gitterdateien für den NTv2-Transformationsansatz".
The accuracy is claimed to be better than 4 cm.

However, a problem could be that this grid shift file transforms from the datum RD/83, not
from DHDN.  EPSG writes about RD/83 (the long/lat coordinate system, EPSG:4745):

   "Consistent with DHDN (CRS code 4314) at the 1-metre level.
    For low accuracy applications RD/83 can be considered the same as DHDN."

And about the underlying datum, Rauenberg Datum/83, (EPSG:6745), EPSG writes:

  "RD/83 is the realisation of DHDN in Saxony. It is the resultant of applying
   a transformation derived at 106 points throughout former East Germany to
   Pulkovo 1942/83 points in Saxony."

I must admit that I don't see how these remarks fit together. If RD/83 is the realisation of
DHDN in Saxony, I would expect that they coincide exactly, rather than at the 1 meter level.
But maybe someone else can explain this, or maybe you can find an answer on
the Saxony web site. (I am not very good at reading German documentation.)

Finally, I noticed that Saxony web site provides a free application, TRANS_SN (light),
which may be exactly what you need. It is probably easier to use than Proj.4.

Good luck!

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 Mikael Rittri
Sent: den 8 maj 2012 16:34
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Using EPSG codes with cs2cs

Amro,

Jose' is right, especially if you want agreement with other data that have been transformed
with those datum shift parameters.

But you wrote:

> My need here is to get as accurate as possible results (cm-level if possible).

Then, a better alternative could be to use the grid shift file BETA2007.gsb. It is not distributed with Proj.4,
but you can find a link at http://trac.osgeo.org/proj/ under Download, Datum shift grids.

If you download it to the directory where the other grid shift files are in Proj.4 (the nad directory),
then you can do

>cs2cs +init=epsg:4326 +to +ellps=bessel +proj=tmerc +lon_0=12 +x_0=4500000 +nadgrids=BETA2007.gsb

13.755944 51.054555

4623220.44      5659181.52 0.00

This result differs by about 1.7 meters from Jose's example.

The BETA2007.gsb file is claimed to give submeter accuracy,
"eine Koordinatengenauigkeit im Submeterbereich". (But maybe it
is still possible that the 7-parameter transformation you cite is more
accurate locally around Dresden.)

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 15:59
To: PROJ.4 and general Projections Discussions
Subject: Re: [Proj] Using EPSG codes with cs2cs

In addition to my previous e-mail, since you have your own datum shift parameters it is better to write the full proj string, instead of using an epsg predefinition. Your rotation angles are in radians but cs2cs expects arc-seconds. They become 1.04, 0.35, -3.08.
According to the map projection definition you give, the command line should be something like:
cs2cs +init=epsg:4326 +to +ellps=bessel +proj=tmerc +lon_0=12 +x_0=4500000 +towgs84=582,105,414,1.040,0.350,-3.080,8.3
13.755944 51.054555
4623218.81      5659181.06 -46.16

Regards

Jose'  Gonçalves

2012/5/7 Jose Gonçalves <jagoncal at gmail.com<mailto:jagoncal at gmail.com>>
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

--
View this message in context: http://osgeo-org.1560.n6.nabble.com/Using-EPSG-codes-with-cs2cs-tp3841592p4957639.html
Sent from the PROJ.4 mailing list archive at Nabble.com.
_______________________________________________
Proj mailing list
Proj at lists.maptools.org<mailto:Proj at lists.maptools.org>
http://lists.maptools.org/mailman/listinfo/proj

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/proj/attachments/20120509/91c600eb/attachment.html>