[Qgis-user] use raster + GCP points + ?? as data

[jr.morreale at enoreth.net]

 On Mon, 11 Jul 2011 23:27:14 -0700, Alex Mandel wrote:
> On 07/11/2011 10:30 PM, Richard Duivenvoorde wrote:
>> Hi all,
>>
>> I have these pile of scanned old maps and can georeference them with 
>> the
>> good working georeferencer plugin in qgis.
>>
>> But do NOT want to really warp the image. Why should we want to 
>> store
>> TWO huge rasters, maybe loosing 'data' contained in the 'original'?
>>
>> So my question: is it possible (for Qgis, but preferebly also with 
>> other
>> tools (wms's) to load data from the original raster, probably
>> accompanied with a txt file with GCP points (or maybe some other 
>> format
>> containing both gcp points and projection/transformation 
>> information)?
>>
>> Is there some 'common' way for the the world of gis?
>>
>> Thanks for any thoughts,
>>
>> Richard Duivenvoorde
>
>
> A world file is the common way. It describes the coordinates of the
> corners, how many units per pixel and what skew if any. See the
> wikipedia page for details.
>
> I believe the georef plugin can save the a world file for you.
>
> Thanks,
> Alex

 It doesn't enable for all the transformation methods.

 Richard > this choice has a huge trade-off with most formats, the time 
 to resample the raster each time the users move the canvas will not be 
 accepted by them. Storage is cheaper and does not interfere with your 
 users. If the size is a huge issue and not the quality of 
 representation, you can reduce the original resolution.