[Proj] Misplaced SHP obtained with PROJ 4.8.0 called from gvSIG CE

[Jorge Arevalo]

On Sun, Aug 25, 2013 at 10:16 PM, Jorge Arevalo
<jorge.arevalo at geomati.co> wrote:
> On Wed, Aug 21, 2013 at 8:15 PM, Hermann Peifer <peifer at gmx.eu> wrote:
>> On 2013-08-21 17:04, Jorge Arevalo wrote:
>>>
>>> Hello,
>>>
>>> I'm trying to fix a bug related with PROJ in gvSIG CE. This desktop
>>> client creates its own JNI wrapper, based on PROJ sources. The
>>> reprojection of shapefiles using grid files works with the wrapper
>>> based on PROJ 4.5.0, but it fails if we construct the same wrapper
>>> based on any upper version of PROJ (PROJ 4.8.0, for example).
>>>
>>> Here, the use case that causes the problem:
>>>
>>> - We want to reproject this shapefile from epsg:23030 to epsg:25830:
>>> https://dl.dropboxusercontent.com/u/6599273/gis_data/EPSG23030_data.zip
>>>
>>> - We want to use this grid file to perform the operation:
>>> https://dl.dropboxusercontent.com/u/6599273/gis_data/sped2et.gsb
>>>
>>> The operation done with the JNI wrapper based on PROJ 4.5.0 works
>>> fine. But if we use PROJ 4.8.0 as base, we get a misplaced file. Here,
>>> a screenshot. In blue, the original shapefile. In green, the shapefile
>>> correctly reprojected (PROJ 4.5.0). In red, the misplaced shapefile
>>> (PROJ 4.8.0)
>>>
>>>
>>> https://dl.dropboxusercontent.com/u/6599273/errors/gvsigce/gvsigce_misplacing_reproj.png
>>>
>>> Debugging, we found the problem is in pj_transform.c. I guess it's
>>> related with the way we pass information to PROJ functions. I've made
>>> a diff between both versions (pj_transform in PROJ 4.5.0 and PROJ
>>> 4.8.0), but I see several changes, and I don't know where to focus.
>>> Any clue?
>>>
>>> Many thanks in advance, and best regards,
>>>
>>
>> I assume that this is your definition of the target SRS:
>>
>> +proj=utm +zone=30 +ellps=GRS80 +units=m +no_defs
>>
>> if yes, you'd have to change it to:
>>
>> +proj=utm +zone=30 +ellps=GRS80 +nadgrids=@null +units=m +no_defs
>>
>> Further reading: Why do I get different results with 4.5.0 and 4.6.0?
>> http://trac.osgeo.org/proj/wiki/FAQ#WhydoIgetdifferentresultswith4.5.0and4.6.0
>>
>> Hermann
>>
>>
>
> Hello Hermann,
>
> Yes, I think that is definitely related with my problem. My SRS
> definition string is incorrect. Now, I need to review the way it's
> built in gvSIG CE. Many thanks for putting me in the right track!
>
>
> --
> Jorge Arévalo
> http://geomati.co

Hello again,

Actually, my SRSs are:

source SRS: +proj=tmerc +lat_0=0.0 +lon_0=-3.0 +k=0.9996 +x_0=500000.0
+y_0=0.0 +ellps=intl +units=m +nadgrids=sped2et.gsb

target SRS: +proj=tmerc +lat_0=0.0 +lon_0=-3.0 +k=0.9996 +x_0=500000.0
+y_0=0.0 +ellps=GRS80 +units=m

First one is obtained from epsg:23030, and second one from epsg:25830.
I've specified sped2et.gsb as grid file (I know it should include the
@ before the grid's name to avoid errors if that file doesn't exist).
Basically, these PROJ4 strings are equivalents to yours, right? So,
the transformation should work with them

Best regards,

-- 
Jorge Arévalo
http://geomati.co