[GRASS-user] Coordinate systems?

GRASS GRASS user
1

I’ve been looking at GRASS for a few months now and for the most can’t determine if I can transform coordinate systems of vector data or not. I’m stuck. All of the data I use (shapefiles) have been in the same reference system (I think it’s the reference system I’m talking about). I’ve been trying to merge two file that are not in the same reference system with no luck. Here are links to them.

Any of these (Q3 FIRM Layer):

http://www.mcgi.state.mi.us/mgdl/?rel=thext&action=thmname&cid=6&cat=Flood+Insurance+Rate+Maps+%28Q3+FIRMs%29

Into this **(**National Flood Hazard Layer (NFHL) Database):

https://msc.fema.gov/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10001&storeId=10001&categoryId=12011&langId=-1&userType=G&type=12

Then select Michigan.

One appears to be in decimal and the other in lat/lon. One has projection file and the other doesn’t

If anyone can shed any light on the process to do this with GRASS or any other Open Source applications it would really be appreciated.

Regards,
Charles Deaton

2
···

You can certainly transform vector and raster data from one Coordinate Reference System to another. As you have probably already realized GRASS is more insistant than some other GIS software regarding CRS. When you first startup a GRASS session you must choose your LOCATION and MAPSET. The LOCATION is defined by a particular CRS, and all the layers in all the MAPSETs under that LOCATION must be in that particular CRS.
To load data into GRASS which is projected into some other CRS, you create a new LOCATION based on that other CRS, and load the new data there. Now switch over to the target LOCATION/MAPSET and run the command v.proj (In the GUI menu it’s Vector->Develop vector map->Reproject Vector map. You set the source LOCATION and MAPSET and the original vector name. Then a new, re-projected vector is created in the target LOCATION/MAPSET.

HTH

On 23/08/2012 18:52, Charles E. Deaton wrote:

I’ve been looking at GRASS for a few months now and for the most can’t determine if I can transform coordinate systems of vector data or not. I’m stuck. All of the data I use (shapefiles) have been in the same reference system (I think it’s the reference system I’m talking about). I’ve been trying to merge two file that are not in the same reference system with no luck. Here are links to them.

Any of these (Q3 FIRM Layer):

http://www.mcgi.state.mi.us/mgdl/?rel=thext&action=thmname&cid=6&cat=Flood+Insurance+Rate+Maps+%28Q3+FIRMs%29

Into this **(**National Flood Hazard Layer (NFHL) Database):

https://msc.fema.gov/webapp/wcs/stores/servlet/CategoryDisplay?catalogId=10001&storeId=10001&categoryId=12011&langId=-1&userType=G&type=12

Then select Michigan.

One appears to be in decimal and the other in lat/lon. One has projection file and the other doesn’t

If anyone can shed any light on the process to do this with GRASS or any other Open Source applications it would really be appreciated.

Regards,
Charles Deaton

This mail was received via Mail-SeCure System.

_______________________________________________
grass-user mailing list
[grass-user@lists.osgeo.org](mailto:grass-user@lists.osgeo.org)
[http://lists.osgeo.org/mailman/listinfo/grass-user](http://lists.osgeo.org/mailman/listinfo/grass-user)

This mail was received via Mail-SeCure System.