Converting between map projections?

[Brian Leybourne]

Hi all,

I'm pretty new to mapmaking. I have followed the Salderan tutorial a couple of times, and quite like what I have managed using it, but I have a quick question.

My world is very pole-centric, as the equator is hostile and essentially impassable (but not completely; that's the point of the story). So although I want to have a nice mercator or mollweide view of the planet, I would also like to be able to work on polar orthographic views (a round hemispheric view with with the pole in the middle and the equator at the edges).

Now, something like FT3 would let me draw a map and switch between the projections, but drawing in FT3 and making the map look even remotely reasonable is tedious, especially if you are making a non-standard looking world (FT3 is great if you want to just end up with a randomly generated earthish planet, but not so great if you want to start with a blank world and draw it). Drawing in photoshop (using Saldferan or similar) is a lot easier, but you're stuck with the one projection you are working in.

Is there an alternative? I thought about making a map in PS and importing it into FT, but it doesn't seem to allow importing. Is there any software that can take a map in one projection and allow you to view/save it in another, if you have drawn the map in a drawing program like PS?

Thanks,
Brian.

[waldronate]

There are many programs out there that can reproject an image. If you're using FT3, I recommend the following workflow (which is quite similar to Ralf Schemmann's old Jhendor tutorial at http://www.jhendor.de/tutorials/cc2-ft.pdf ):

1) Use FT3 ( http://profantasy.com/to produce a polar aspect map grid at the resolution that you desire (e.g. Lambert Azimuthal Equal Area projection output to a 4kx4k PNG file LambertAzEqArea_Polar5deg.png ).
2) Use this projection template as an overlay layer in Photoshop and paint your height map in the background. The extremely lazy among use might just rough it in and use something like the process described in http://www.cartographersguild.com/ma...und-lands.html to finalize things.
3) Use ReprojectImage ( http://www.ridgenet.net/~jslayton/ReprojectImage.zip ) to reproject the world data to the equirectangular projection that FT expects as its binary input.
4) Use Wilbur ( software ) to flip the image vertically and to convert the reprojected image into a .mdr file.
5) Use FT3 and create a new world (File>>New) using the binary mdr file saved in Wilbur.

If you just want to use a picture in FT3 but not height data, you can use the image overlays feature of FT3 to load the output of ReprojectImage directly.

[Brian Leybourne]

There are many programs out there that can reproject an image. If you're using FT3, I recommend the following workflow (which is quite similar to Ralf Schemmann's old Jhendor tutorial at http://www.jhendor.de/tutorials/cc2-ft.pdf ):

Awesome, thanks for the reply!

I will give this a go. I found g.projector last night from NASA, which is really good but it assumes you're starting with a rectangular mercator-type map; there doesn't seem to be any way of starting from a different projection, and I would rather start with an orthographic view and build from there, so your mini-tutorial looks to be just the ticket!

Thanks again,
Brian.

[Mogg01]

I'm trying to follow this process in an attempt to move the equator of a map that I'm working on (it was shifted about 45 degrees north), but ReprojectImage isn't available anymore. Does someone have a copy that they could send to me, or a working link?

[johnvanvliet]

Mogg01

without seeing YOUR map
I can only make guesses

GDAL remaps datums very well ( gdal_warp)

This is a commandline tool ( on windows "cmd.exe")

there is a kind of GUI
Qgis

has a point and click GUI for gdal
and a tool for Geo-referencing the original image

now sometimes for somethings a easier tool " MMPS" - also a commandline tool ( on windows "cmd.exe")
can remap the image
http://www.users.globalnet.co.uk/~arcus/mmps/

[waldronate]

I'm trying to follow this process in an attempt to move the equator of a map that I'm working on (it was shifted about 45 degrees north), but ReprojectImage isn't available anymore. Does someone have a copy that they could send to me, or a working link?

Try http://www.fracterra.com/ReprojectImage.zip to get ReprojectImage. My ISP killed the ridgenet.net domain without any particular warning and I eventually moved everything to a new host. Everything that was at http://www.ridgenet.net/~jslayton is now at http://www.fracterra.com for your convenience. I don't have any way to path all of the posted paths here on the guild.

[Mogg01]

Awesome, thanks for the super quick responses to a dead thread! ReprojectImage worked like a charm, and my project is back on track! I'll probably mess around with GDAL and MMPS at some point here to see what I can do with them, but I'm already trying to learn 4 new tools for this project, and was hoping to keep the beginning simple. I (obviously) made this account just to beg for ReprojectImage, but given how helpful people seem, I'm thinking I'll hang around and start trying to contribute.