Bug#765463: gdal-bin: GDAL and proj4 disagree on some co-ordinate transformations

[Matthew Somerville]

Package: gdal-bin
Version: 1.9.0-3.1
Severity: normal

Hi,

On stable Debian, with gdal-bin 1.9.0-3.1 and proj-bin 4.7.0-2, different
results are returned for the same co-ordinate transformations:

$ echo '-1.3893433684943819 52.7297093932173411' | cs2cs +init=epsg:4326 +to +init=epsg:27700
441335.00   314849.00 -48.92
$ testepsg -t epsg:4326 epsg:27700 -1.3893433684943819 52.7297093932173411 0
(-1.389343,52.729709,0.000000) -> (441334.824686,314851.829623,-47.495477)

The results differ by a few metres. Looking at the internal definitions, we see
the following (testepsg comes from gdal-bin, cs2cs from proj-bin):

$ testepsg epsg:27700
...
    +towgs84=375,-111,431,0,0,0,0 +units=m +no_defs
...

$ cs2cs -v +init=epsg:27700
...
# +towgs84=446.448,-125.157,542.060,0.1502,0.2470,0.8421,-20.4894
...

The "towgs84" parameters are different - a 7-parameter version with proj4, but
a 3-parameter version with GDAL. I would have assumed that both packages both
used the same underlying data (which I believe is libgeotiff) on the same
system, but I assume different versions of the data are bundled inside one or
both of these packages, leading to this issue. I tracked the libgeotiff change
down to http://trac.osgeo.org/geotiff/changeset/2023/trunk/libgeotiff/csv/gcs.csv
- though I would have thought the 7-parameter version was more accurate (not
sure!)?

Anyway, I'm not sure if this has a solution, but it took long enough to track
down (PostgreSQL using proj4, Django using GDAL, so different results depending
where the transformation takes place) that I thought I'd open a report for it
in case anyone else came across the same issue.

ATB,
Matthew

-- System Information:
Debian Release: 7.6
  APT prefers stable-updates
  APT policy: (500, 'stable-updates'), (500, 'stable'), (50, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 3.2.0-4-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages gdal-bin depends on:
ii  libarmadillo3          1:3.2.3+dfsg-1
ii  libc6                  2.13-38+deb7u4
ii  libcurl3-gnutls        7.26.0-1+wheezy10
ii  libdap11               3.11.1-11
ii  libdapclient3          3.11.1-11
ii  libdapserver7          3.11.1-11
ii  libepsilon0            0.9.1-2
ii  libexpat1              2.1.0-1+deb7u1
ii  libfreexl1             1.0.0b-1
ii  libgcc1                1:4.7.2-5
ii  libgdal1               1.9.0-3.1
ii  libgeos-c1             3.3.3-1.1
ii  libgif4                4.1.6-10
ii  libhdf4-0-alt          4.2r4-13
ii  libhdf5-7 [libhdf5-7]  1.8.8-9+b1
ii  libjasper1             1.900.1-13
ii  libjpeg8               8d-1+deb7u1
ii  libkml0                1.3.0~r863-4.1
ii  liblzma5               5.1.1alpha+20120614-2
ii  libmysqlclient18       5.5.38-0+wheezy1
ii  libnetcdfc7            1:4.1.3-6+b1
ii  libodbc1               2.2.14p2-5
ii  libogdi3.2             3.2.0~beta2-7
ii  libpng12-0             1.2.49-1
ii  libpoppler19           0.18.4-6
ii  libpq5                 9.1.13-0wheezy1
ii  libproj0               4.7.0-2
ii  libspatialite3         3.0.0~beta20110817-3+deb7u1
ii  libsqlite3-0           3.7.13-1+deb7u1
ii  libstdc++6             4.7.2-5
ii  liburiparser1          0.7.5-1
ii  libxerces-c28          2.8.0+deb1-3
ii  odbcinst1debian2       2.2.14p2-5
ii  unixodbc               2.2.14p2-5
ii  zlib1g                 1:1.2.7.dfsg-13

gdal-bin recommends no packages.

Versions of packages gdal-bin suggests:
ii  python-gdal  1.9.0-3.1

-- no debconf information