[GRASSLIST:5790] Re: GRASS Novice Needs Help

[John Ronan]

On 15 Feb 2005, at 18:49, Ian MacMillan wrote:

> John,
> I think your problem is that your Irish grid is in transverse 
> mercator, which means the units of measurement is meters, not degrees. 
>  Typically your coordinates will be measured in several hundred 
> thousand to millions of meters.  Latlong locations measure everything 
> in degrees (like you have).  Somehow, you will need to get the correct 
> coordinates in meters for your irish grid first, and then r.proj into 
> your latlong grid.  Or mebbe you can try to just go straight into your 
> latlong grid?  Not sure if this is super helpful but mebbe this can 
> help get you started.
>
Ok, I'm not following at all here...

Though I think I know what your getting at.. its not as simple 
converting from one projection system to another.

I've got the tiles in Irish Grid, and I can export them and gdalwarp 
them to unprojected lat/long which work fine (in xastir).  As I can 
figure out the correct co-ordinates in Irish Grid (I had to in order to 
reproject the tiles in the first place) I'm not sure exactly how that 
helps me?

Of course the question remains, is this the correct way to 'patch' two 
'tiles' together, which is my ultimate goal.

Regards
John
--
John Ronan <jronan at tssg dot org>, +353-51-302938
Telecommunications Software &  Systems Group,  http://www.tssg.org