Bug Exporting ECW-Data

schlenn

Hi,

I think there is a BUG when exporting ECW-Data with GM 10.01. Seems that the Projection isn't put correctly in the ECW-file.

I used an OziExplorer-Map with Mercator-Projection and WGS84 datum and export it with the same projection/datum. When I load the exported ECW-file with GPSMapEdit, I get the following error:

Loading data from file 'C:\Users\michael\Documents\Karten\Nepal\Kathmandu\kathmandu_street_teil2.ecw'...
Datum: WGS84.
WARNING: Unsupported projection: LOCAL.
Supported projections are Lat/Lon, Transverse Mercator, Mercator, UTM.
ERROR: loading has terminated.

I checked that with an HEX-Editor. The file exported with Globalmapper 10.01 has "LOCAL" at byte 09 (see screenshot).



When exporting the same map with Globalmapper 9.03 everything works fine. The HEX-Editor shows "MRAFRICA" at byte 09. This file loads perfectly with GPSMapEdit.



Bug or feature

Thanks,
Michael

global_mapper

Michael,

I just gave this a try in the latest build (soon to be v10.02) and the MRAFRICA projection was properly written out on export. Did you have your projection set up exactly as a Mercator projection with WGS84 as the datum, meters as the units, and all of the parameters at their defaults (i.e. a scale of 1.0 and zeroes for the rest)? It would have to be setup just like that for the MRAFRICA projection to apply.

I have placed a new build at http://www.globalmapper.com/global_mapper10.zip with the latest build that I am using for you to try. Simply download that file and extract the contents into your existing v10.xx installation folder to give it a try.

Let me know if I can be of further assistance.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

schlenn

Hi,

with the 10.02-Version everything works like a charme now. Seems to be a bug only in the 10.01

Thanks,
Michael

schlenn

Unfortunately I again have an issue with the ECW-export. But now I get an error with GM 9.03 and 10.02.

I have a map of Nepal here with Gauss Krueger 3° Zone 29. I rectify it using Transverse Mercator with the following settings:



I also use these settings when viewing the map. But when I export the data to an ECW-file, the projection is set to "LOCAL", as one can see when opening the ecw-file with an HEX-editor:



And GPSMapEdit fails to load the map with the following error:

Loading data from file 'C:\Users\michael\Desktop\test.ecw'...
WARNING: Unsupported datum: . The image position may be shifted.
WARNING: Unsupported projection: LOCAL.
Supported projections are Lat/Lon, Transverse Mercator, Mercator, UTM.
ERROR: loading has terminated.
2 warning(s).
Load time is 0.02 s.

Regards,
Michael

global_mapper

Michael,

The problem is that the ECW format only supports a finite set of known projection and datum names and does not support storing an arbitrary base projection (like Transverse Mercator) with some arbitrary set of parameters. So if the ECW projection and/or datum name tables don't have a known name for your projection and datum, then Global Mapper is forced to store 'LOCAL' as the value as there is not one defined to use for the ECW format.

If you choose to save a PRJ file with your export that will contain your full projection definition, although I'm not sure if GPSMapEdit supports that or not. Is it possible for you to use the GeoTIFF format instead as it supports a much more complete projection specification?

Let me know if I can be of further assistance.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

schlenn

Thanks for the hints.

I thought that ECW is capable to store Transverse Mercator, because GPSMapEdit said "Supported projections are Lat/Lon, Transverse Mercator, Mercator, UTM".

Unfortunately, GPSMapEdit don't read the PRJ-File - and the supported files for raster maps are only JPEG2000, ECW and OziExplorer.

So JPEG2000 and EWC seem not to work. Is it possible to convetr the Map into OziExplorer with GM?

Thanks,
Michael

global_mapper

Michael,

ECW does support some specific Transverse Mercator projection definitions, just not the one that you are using. Which OziExplorer format does GPSMapEdit support? I am surprised that it doesn't support the GeoTIFF format as it is by far the most common one out there.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

global_mapper

Michael,

You might also try setting your projection to Geographic/WGS84 and export your ECW file with that projection. It will get stored then and should be properly positioned in GPSMapedit as I suspect that is the projection that all of the map editing is done with in that application.

Thanks,

Mike
Global Mapper Support
support@globalmapper.com

schlenn

Mike,

thanks a lot - changing the projection to Geographic/WGS84 works fine with GPSMapEdit!

Another possibility is to switch to UTM/WGS84, which is very similar to the GaussKrueger-projection. UTM is also read by GPSMapEdit without any problems.

Thanks!

Michael