[GRASSLIST:2701] Re: stitching geotiffs

[Martin du Saire]

Outstanding!  Thank you Richard and  Glynn.  I think I may eventually have 
to r.patch the individual maps.  I was playing around with two maps within 
a single zone, and the r.stats -a -n map1,map2 output did not reflect what 
I expected to be the composite of the two (Actually, the numbers made no 
sense at all).  One last question:

Without having specific datum in my adjacent zones (14, 16), is there some 
way to make upper-bound estimates on the amount of distortion resulting 
from the r.proj method=nearest (the maps are land-use/cover)?

Thanks again.

Martin


At 10:06 AM 2/20/2004 -0700, you wrote:
>Martin du Saire wrote:
>
>>At 04:01 PM 2/19/2004 -0700, you wrote:
>>
>>>Martin du Saire wrote:
>>>
>>>>Hi,
>>>>I am a newbie to GRASS (XT, Cygwin/XFree86; GRASS5.0) and GIS trying to 
>>>>stitch together a set of NLCD Geo-Tiff  (USGS Landsat-5, etc.) data 
>>>>files for a set of contiguous states in the US.  I finally figured out 
>>>>how to import them using r.in.gdal -o.  (If there is some inherent 
>>>>problem with overriding the projection checking, please let me know.)
>>>
>>>
>>>If you are importing an image in UTM Zone X into a location defined as 
>>>UTM Zone X, then you are doing the correct thing by using -o. (You 
>>>should not use -o to import Zone X into a location of Zone Y). You may 
>>>also want to use -e, which extends the location if needed.
>>
>>So I can import a Zone X map into a Zone Y location?  Is this any 
>>better/worse than using r.proj?  The bulk of my area of interest is in a 
>>single UTM zone (Zone Y), so maybe the distortions generated by importing 
>>Zone X and Zone Z maps into a location of Zone Y will be small??
>
>No. Sorry I was not clear. You must use r.proj. Import Zone 14 maps into a 
>Zone 14 location. Zone 15 into a Zone 15 location, etc. And then use 
>r.proj to bring your Zone 14, and Zone 16 maps into your Zone 15 location.

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