Converting Equirectangular Map to Mercator Without Losing High Resolution

[Question-Asker]

Hello!

I was wondering if anyone knows how I can convert an Equirectangular projected map to a Mercator projected one without reducing the resolution (by too much). I've seen other posts on here about this but I haven't been able to figure it out yet. I've tried using G.Projector but it drastically reduces the resolution to the point of uselessness, and I've tried using flex projector but it doesn't appear to be able to import custom maps. If anyone knew of a program or a way to do it manually on a program like paint.NET I would be very appreciative.

[waldronate]

Please define "high resolution". Something like the GDAL tools should be able to handle it, but a lot will depend on what you have and how comfortable you are with command-line tools.

[Question-Asker]

Please define "high resolution". Something like the GDAL tools should be able to handle it, but a lot will depend on what you have and how comfortable you are with command-line tools.

Thanks for the reply! The resolution I'm talking about is a 43200 x 21600 pixel map. I'm willing to shrink that size a bit if absolutely necessary but I'd prefer not to. I don't have any experience with command-line tools but I'm willing to learn more about them to get this project done.

[waldronate]

Which 1km data set are you using for your input? Natural Earth?

What is it that you plan to do with the reprojected map?

https://gis.stackexchange.com/questi...ar-to-mercator might be of use to you as it shows how to take a whole-world raster image (ETOPO1 GeoTIFF) in the Equirectangular projection (epsg:4326) and convert it to a cropped GeoTIFF in the Mercator (EPSG:3857).
https://gdal.org is the home of the GDAL software (it has useful reference material). https://www.qgis.org/en/site/ is its GUI friend QGIS.
https://www.gisinternals.com/release.php is a good Windows GDAL distribution that you need to actually make the command-line things run. I recommend the x64 distribution if possible because there aren't really too many 32-bit OS versions left out there these days.
Your best bet is likely to be QGIS if you're not familiar with command-line tools, but then you get to learn QGIS as opposed to plunking down some commands for a one-shot activity.

The program should have no problems handling 43200x21600, but you'll probably need to handle the vertical extents because the north and south poles on Mercator are at infinity in its pure form. The stack exchange link above shows how to crop the input to a smaller shape.

[Question-Asker]

Which 1km data set are you using for your input? Natural Earth?

What is it that you plan to do with the reprojected map?

https://gis.stackexchange.com/questi...ar-to-mercator might be of use to you as it shows how to take a whole-world raster image (ETOPO1 GeoTIFF) in the Equirectangular projection (epsg:4326) and convert it to a cropped GeoTIFF in the Mercator (EPSG:3857).
https://gdal.org is the home of the GDAL software (it has useful reference material). https://www.qgis.org/en/site/ is its GUI friend QGIS.
https://www.gisinternals.com/release.php is a good Windows GDAL distribution that you need to actually make the command-line things run. I recommend the x64 distribution if possible because there aren't really too many 32-bit OS versions left out there these days.
Your best bet is likely to be QGIS if you're not familiar with command-line tools, but then you get to learn QGIS as opposed to plunking down some commands for a one-shot activity.

The program should have no problems handling 43200x21600, but you'll probably need to handle the vertical extents because the north and south poles on Mercator are at infinity in its pure form. The stack exchange link above shows how to crop the input to a smaller shape.

I'm using NASA's Blue Marble Topography Maps: https://visibleearth.nasa.gov/images...ography/84331l

And I plan on trying to 3D project the world's height.

I will look into QGIS and the others thank you for your help!

[Question-Asker]

Which 1km data set are you using for your input? Natural Earth?

What is it that you plan to do with the reprojected map?

https://gis.stackexchange.com/questi...ar-to-mercator might be of use to you as it shows how to take a whole-world raster image (ETOPO1 GeoTIFF) in the Equirectangular projection (epsg:4326) and convert it to a cropped GeoTIFF in the Mercator (EPSG:3857).
https://gdal.org is the home of the GDAL software (it has useful reference material). https://www.qgis.org/en/site/ is its GUI friend QGIS.
https://www.gisinternals.com/release.php is a good Windows GDAL distribution that you need to actually make the command-line things run. I recommend the x64 distribution if possible because there aren't really too many 32-bit OS versions left out there these days.
Your best bet is likely to be QGIS if you're not familiar with command-line tools, but then you get to learn QGIS as opposed to plunking down some commands for a one-shot activity.

The program should have no problems handling 43200x21600, but you'll probably need to handle the vertical extents because the north and south poles on Mercator are at infinity in its pure form. The stack exchange link above shows how to crop the input to a smaller shape.

QGIS is working like a charm, thank you again! The only problem I'm having is I'm confused how to export the image in the exact quality I imported it as. When I try and export it, it's quality is significantly reduced.

[johnvanvliet]

I work with planetary data all the time , but it has been a while since i used the QGis tools as a GUI for GDAL

As i recall you need to state the resolution of the output image ( some place in the qgis gui ) i can not recall at this time where it is .

[Question-Asker]

I work with planetary data all the time , but it has been a while since i used the QGis tools as a GUI for GDAL

As i recall you need to state the resolution of the output image ( some place in the qgis gui ) i can not recall at this time where it is .

Thanks for your reply. I seem to to able to export in the quality I want, but it seems like the fact I've changed the projection of the map is ignored by QGIS

This is what the cropped area on my QGIS looks like before being exported:

memrcator.PNG

But once it's exported its squashed back to resembling a Equirectangular projection

squashed.jpg

You wouldn't happen to know what I'm doing wrong?

[johnvanvliet]

i think you might be exporting the wrong layer of the image .
i will go and reinstall Qgis ( i run Linux OS only , NO microsoft ) in a little bit and have a go at the Whole Earth data i have and see what is going on

[waldronate]

Have you tried something like https://freegistutorial.com/how-to-e...ormat-on-qgis/ to see if it works?
QGIS and I have never really gotten along well the few times I've installed it, so I'm afraid I can't be a whole lot of help, regardless of the OS you install it on.