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I am trying to stitch together several GEO Tiffs that come in pairs (north -south) but when i load them into QGIS they display completely overlapped. That is the north south pair match up ok (display next to one another) but when I add a second north-south pair they completely overlap the previous layers rather than being positioned next to the previous pair.

I recently found a tutorial that had a command in qgis to lay them out of the canvas correctly but I cannot find it now for some reason.

Has anyone else had this problem ??

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the tiffs are not representing the same area..right? – vinayan Jul 5 '12 at 0:37
Also, are you sure the rasters are GEOtiffs? Run the command gdalinfo on the files to check their coordinate reference system. That's in the menu Raster->Misc->Information. Have a look at the PROJCS line in the output. – Micha Jul 5 '12 at 17:11
Yes they have TFW files associated with them. – MB. Jul 6 '12 at 12:43
No they are adjacent regions – MB. Jul 6 '12 at 12:44

1 Answer

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If they load at the same place, it is because they have the same coordinates ... or no coordinates ! are they in the good place (compare with vectors i.e.) or are they in (0,0), or degrees are loaded in meters (not the same projection), the tfw do not have exactly the same name, these are the most common errors. If not, open the 2 tfw with a text editor and compare the coordinates (the 2 last lines). You must have a difference between the two tfw in X (or Y)only which is the number of pixels by the resolution. That's to say if you have a raster of 542 pixels of 1 meter, the difference will be 542m.

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ALB N 63.6518920000 0.0000000000 0.0000000000 -63.6518920000 -423762.1870290463 253071.4202335640 ALB S 63.5907290000 0.0000000000 0.0000000000 -63.5907290000 -423542.4395738543 -5396.3742254743 Alt N 63.6486180000 0.0000000000 0.0000000000 -63.6486180000 -424268.6746073976 278748.8959633287 Alt S 63.6289870000 0.0000000000 0.0000000000 -63.6289870000 -420284.1132081475 18624.4939538786 – MB. Jul 8 '12 at 20:04
Above I have copied in the info from the TFW as you can see they should align the N / S items but the lat longs are quite different for ALT / ALB. and yet in QGIS on the screen they overlap. Could it be some setting in QGIS for the worksapce size needing to be expanded ??? – MB. Jul 8 '12 at 20:06
@MB, have you compared your TFW files to the output from gdalinfo (after temporarily moving the TFW files to another directory)? Could be any embedded georef is overriding your TFW files. – dakcarto Jul 8 '12 at 21:49
I'll give it a try thanks – MB. Jul 9 '12 at 2:02

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