[GRASSLIST:5798] Re: GRASS Novice Needs Help

[John Ronan]

>
> [as noted, there are wrong; what does "gdalinfo" say about the TIFF?
>  are you sure the TIFF isn't starting out in lat/lon already?]
Ok, the tiff generated by r.out.gdal give

gdalinfo os2410poly1.tif
Driver: GTiff/GeoTIFF
Size is 4724, 4724
Coordinate System is `'
Origin = (-7.415917,52.330316)
Pixel Size = (0.000063,-0.000038)
Corner Coordinates:
Upper Left  (  -7.4159169,  52.3303161)
Lower Left  (  -7.4159169,  52.1487398)
Upper Right (  -7.1200431,  52.3303161)
Lower Right (  -7.1200431,  52.1487398)
Center      (  -7.2679800,  52.2395280)

>> nsres:      0.15
>> ewres:      0.55
>> rows:       1
>> cols:       1
>
> so resolution is 15cm x 55cm and everything is contained in one single
> data cell.
>
When you explain it like that, it doesn't make much sense does it? Hmmm
>
[snip]

> 38462 rows X 76923 columns! You've chosen a very large area of land to
> map out a 5m resolution!
>
Well I was trying to make it large enough :)

> To patch:
>
> g.region rast=map1,map2
>  ## strech region to contain both maps
>
Ok, something funny going on here thats the output from g.region -p 
from both maps individually

GRASS 5.7.0:~ > g.region -p
projection: 99 (Transverse Mercator)
zone:       0
datum:      ire65
ellipsoid:  modif_airy
north:      52.33030351
south:      52.14872735
west:       -7.41558677
east:       -7.11971255
nsres:      0.00003844
ewres:      0.00006263
rows:       4724
cols:       4724

GRASS 5.7.0:~ > g.region -p
projection: 99 (Transverse Mercator)
zone:       0
datum:      ire65
ellipsoid:  modif_airy
north:      52.32853668
south:      52.14617722
west:       -7.12318884
east:       -6.8268459
nsres:      0.0000386
ewres:      0.00006273
rows:       4724
cols:       4724

Which doesn't at all agree with Tom's follow on email, Hmmm.

I suspect I've done something else stupid. When GRASS asked me for the 
tie points for the rasters, I supplied the eastings northings in 
latitude and longitude. Which I'm assuming now given that my 
co-ordinate system is in Meters that this is completely wrong. That 
wouldn't explain how they seem to display correctly though.

Tom, how did you work out the tie points in meters?

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