[Qgis-user] Assigning/warping projections

[Lee Mueller]

Jean-Claude,

I was able to compile the utility in question. Unfortunately, after
utilizing it I am doubting it is the answer to my question. At the very
least I was able to confirm the ecw file contains projection data:

>>> ecwhed WYANDOTTE_NE.ecw
Datum = NAD83
Projection = MICH_GEOREF
Origin = (731867.577255, 192959.525684)
Pixel Size = (1.000000, -1.000000)
Corner Coordinates:
Upper Left = (731867.577255, 192959.525684)
Upper Right = (737276.577255, 192959.525684)
Lower Left = (731867.577255, 185830.525684)
Lower Right = (737276.577255, 185830.525684)

Again, I utilized gdalwarp in an attempt to reproject this raster from
Michigan Georef (EPSG:3078) to UTM Zone 17 (ESPG:26917).
I receive the following error:

ERROR 1: Unable to compute a transformation between pixel/line
and georeferenced coordinates for
/home/lee/documents/gis/detroit/aerial/WYANDOTTE_NE/WYANDOTTE_NE.ecw.
There is no affine transformation and no GCPs

Additionally, in the QGIS layer if I choose to "set layer CRS" when opening
the dialog it says "this layer appears to have no projection specified. By
default, this layer will not have its projection set to that of the project,
but you may override this by selecting a different projection below."

Qgis automatically assigns:

+proj=omerc +lat_0=45.30916666666666 +lonc=-86 +alpha=337.25556 +k=0.9996
+x_0=2546731.496 +y_0=-4354009.816 +gamma=0 +ellps=GRS80
+towgs84=0,0,0,0,0,0,0 +units=m +no_defs


Which is essentially the correct projection. However, if I attempt to set
EPSG:3078, hit okay, and return the dialog, nothing has changed.


I'm assuming this all has to do with your suggestion to edit the ecw_cs.wkt.
I found and examined the file, and neither of the projections I need to use
seem to be in there. How would I go about correctly making entries for
EPSG:3078 and EPSG:26917? Google could not provide adequate results (or
operator error due to poor keyword choice --likely).

My apologies for elementary questions. My previous experience with GIS is
limited to mapmaking and usually my projections have behaved. I appreciate
any help or guidance you or others can offer.

all the best,
Lee


On Fri, Jul 1, 2011 at 3:47 AM, Jean-Claude Repetto <jcrml2 at mxm.eu> wrote:

> Le 30/06/2011 19:28, Lee Mueller a écrit :
>
>  First, will I be able to use EPSG values for the projection assignment
>> with this method?
>>
>
> Look at the file ecw_cs.wkt for the list of the datums and projections that
> GDAL supports. If needed, you can add other projections and datums to this
> file.
>
>
>  Second, I'm getting the following error on make. ECW sdk was previously
>> installed from source the same time as qgis.
>>
>
> I told you in my previous mail : The libtool file should probably be
> updated. Try to compile it manually :
>
> g++ -o ecwhed -l pthread  ecwhed.cpp /usr/lib64/libecwj2.a
>
> (the path for libecwj2 may be different on your system).
>
> Jean-Claude
>



-- 
all the best,

Lee Mueller
Natural Resource Consultant
 MuellerL at NorthwoodsResources.com
248.266.0659

Northwoods Natural Resources
www.northwoodsresources.com
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