[GRASSLIST:10653] Re: r.proj takes a very long time / does not complete

[Paul Kelly]

Hello Hamish

On Wed, 1 Mar 2006, Hamish wrote:

>>> That would be very handy if r.proj could estimate the best output
>>> resolution as well. I remember there was some discussion about
>>> completely replacing r.proj warper with gdal warper. Any news?
>>
>> The way I see it is that they perform two different, complementary
>> functions. gdalwarp is useful if you have a whole map/image you want
>> to  convert to a new projection and not lose any of the data. r.proj
>> is useful  if you already have a region of interest you're working on
>> in the GIS, and  want to import only the portion of the larger
>> map/image that covers this region, at the same resolution and with the
>> same boundaries etc. as your  existing maps in your location.
>>
>> Does that make sense?
>
> (again, sorry for very late responses)
>
> I don't know if this goes for r.proj method=nearest,bilinear,cubic as
> well, but for i.rectify the idea was to use the GDAL warp *API*, not
> the gdalwarp program.

Hmm yes. I suppose my point may have been (can't remember too well as was 
long ago!) that in the usage scenario for r.proj that I suggested, the 
less advanced r.proj algorithm would tend to be adequate for what would 
likely be a smaller area to be re-projected etc. The limitations came more 
into play when you were re-projecting a whole map, which gdalwarp was 
better suited for anyway.

But yeah no technical argment at all against improving the r.proj warping 
by using GDAL functions.

Paul