QGIS Georeferencer quetion

[vorropohaiah]

This is probably a long-shot, but here goes.

I use QGIS to change the projections of my maps, using the Georeferencer functon. Normally I enter non-equirectangular projections, plot the co-ordinates and export the image in an equirectangular procjetion. This is useful for projecting a regional map onto a sphere to see what the 'real' projection looks like.

anyway. I'm trying to do the opposite - I'm drawing an equirectangular map and have imported it into the QGIS Georeferencer, entered the co-ordinates and am trying to export in a non-equirectangular (lambert equal area, if it matters), but it just keeps on exporting it was equirectangular. I'm not sure If im doing anything wrong. I've tried exporting in different projections and after rendering, the exported image is always identical to the original one.

Can anyone help?

EDIT: I;ve tried G projector, Winski.net, Wilbur and Fractal Terrains and none work in the resolution I need. I am sure that QGIS can do this, its just that I'm lacking the know-how to do it.

[Repporio]

Are you trying to export the layer directly (right click>export>save as) or using a print composer? I know exporting directly doesn't work for me.

[vorropohaiah]

I'm trying to export it in a different projection. The imported image is a .jpg, and the export is by default a .tif file.

here is what I am doing when saving the file.



Ive never had issues in the past when doing it the other way round - importing a non-equirectangular projection and exporting as an equirectangullar. But for some reason I'm trying to do the opposite now and all exports are remaining equirectangular, with no changes.

[Repporio]

Yeah, I can't seem to get it working either. I would suggest georeferencing your map into the project and then use the Raster>Projections>Warp(Reproject) to create a new raster with your desired projection and then export that raster. Not a frequent user of QGIS though. Someone with more experience might be able to give a better answer.

[vorropohaiah]

I would suggest georeferencing your map into the project and then use the Raster>Projections>Warp(Reproject) to create a new raster with your desired projection and then export that raster.

Ive only ever used the georeferencer function so the rest of it is chinese to me. Wouldnt i have to enter the coordinates though as otherwise how will it know how to reshape it? This is a regional map, not a full world map.

[Repporio]

Just to make sure I understood (english is not my main language) you have a regional map with the equirectangular projection you want to get in a lamberts equal area.


Something like this.


If that is the case then open it in the georeferencer and set the target and raster SRS to WGS 84 and define the extent.


You should then have it in the project like so, although without the background map.


You can then reprojected it using the warp function where you can set the desired target projection and save location.





Using a very low res image but I hope I got my point through
Hope I understood your problem correctly. If I did then this should get you what you want.

[vorropohaiah]

thanks - I do the first 2 steps all the time, the other way round (non equirectangular to equirectangular) but for some reason this is not working out - no matter what output projection i choose the rendered exported file always looks identical to the equirectangular one.

How do I get from the 2nd image to the third one please?

[Repporio]

In the bottom of the Transformation Settings you can toggle "Load in QGIS when done". After performing the output should be loaded in the main QGIS window

[vorropohaiah]

Grrr. I really thought that was going to be it, but no luck. I keep on getting this error. I'm sure I must be doing something wrong, but for the life of me I can't figure out what it is

[Ilanthar]

If I'm not wrong (I've not read everything, I must confess), you could just use Gprojector. It's using equirectangular projections to turn them into the projection you want (there's a wide range of them).

Available here.