Hi!
Originally I have a map that is rectangular along the latitude (original map). I want to map a map that can be more a square rather than a rectangle (desired map). Could you recommend me a projection for accomplishing this?
Many thanks in advance!
Cartesian projection? -JX?/?
Sorry, I was not specific enough. I am trying to use Mercator projection -JM, is it possible to do something like -JMX/Y?
Then do your plot normally and play around with psconvert. Though, semantic matters: it won’t be mercator 
If you want a square Mercator plot you will need to explore what w/e/s/n gives that projected area. See mapproject -I for help. But obviously cannot do things like -JMX/Y since those dimensions are not set separately.
Thanks!!!
Thanks Paul!!!
Here’s a brute-force way to do it.
I know the width is 10c - that’s specified by me.
So I use mapproject -Wh to give me the height of the plot, and tune my -R so that the height becomes as close to the specified width (= 10c) as possible, by iteration:
$ gmt mapproject -JM10c -R0/10/60/66 -Wh
13.2507630607
$ gmt mapproject -JM10c -R0/9/60/66 -Wh
14.7230700674 <-- oops, wrong direction
$ gmt mapproject -JM10c -R0/10/60/66 -Wh
13.2507630607
$ gmt mapproject -JM10c -R0/13/60/66 -Wh
10.1928946621
$ gmt mapproject -JM10c -R0/14/60/66 -Wh
9.46483075763
$ gmt mapproject -JM10c -R0/13.5/60/66 -Wh
9.81538004495
$ gmt mapproject -JM10c -R0/13.8/60/66 -Wh
9.60200221788
$ gmt mapproject -JM10c -R0/13.4/60/66 -Wh
9.88862914976
$ gmt mapproject -JM10c -R0/13.3/60/66 -Wh
9.96297974487
$ gmt mapproject -JM10c -R0/13.2/60/66 -Wh
10.0384568642
$ gmt mapproject -JM10c -R0/13.25/60/66 -Wh
10.0005758949 <-- close enough
Thanks Andreas!