Failed to specify the suffix for latitudes (i.e. N/S) in the polar coordinate system (-Jp, -JP)

[zhong-yy]

Description of the problem
I wanted to plot data that are given in polar coordinates (latitude, radius), so I chose the linear projection -JP. But I encountered the following problems:

1. The angle was treated as longitude by default rather than latitude, so the suffix was W or E.
2. The options +llabel and +uunit didn't work under the projection with polar coordinates -JP.

Full script that generated the error

Here is a minimum working example:

gmt begin Jp jpg E300
    gmt set FORMAT_GEO_MAP ddd:mm:ssF
    gmt basemap -JP5c+z+t0 -R-30/30/4371/6371 -Bxa15f+u" N" -Bya+l"Depth (km)" -BWNse
gmt end show

I have tried -JP3c+z+t0+a, but it didn't work.

Actual outcome

Expected outcome

I want to change W (E) to S (N), like this:

System information

• Operating system: Ubuntu20.04
• GMT version (gmt --version): 6.1.1

[PaulWessel]

Thanks for the post. I guess GMT cannot know what the angular measures are, so it will need to be told. It looks like it assumes these are always longitudes. I think we need to contemplate a situation where we can communicate to -JP the following

1. The angles are longitude: Formatting will be as for longitude.
2. The angles are latitude: Formatting will be as for latitude.
3. The angles are just angles: Formatting will be for angles with degree symbol only.

I am guessing we need to add a new modifier to -JP|p, e.g. +kkind, where kind may be x (longitude) or y (latitude). The default would just be degrees.

Alternatively, we use -f0x and -f0y instead to indicate the same information.

Other thoughts on this, @joa-quim, @meghanrjones and @seisman ?

[maxrjones]

Thanks for the post. I guess GMT cannot know what the angular measures are, so it will need to be told. It looks like it assumes these are always longitudes. I think we need to contemplate a situation where we can communicate to -JP the following

1. The angles are longitude: Formatting will be as for longitude.

2. The angles are latitude: Formatting will be as for latitude.

3. The angles are just angles: Formatting will be for angles with degree symbol only.

I am guessing we need to add a new modifier to -JP|p, e.g. +kkind, where kind may be x (longitude) or y (latitude). The default would just be degrees.

Alternatively, we use -f0x and -f0y instead to indicate the same information.

Other thoughts on this, @joa-quim, @meghanrjones and @seisman ?

This solution seems good to me.

[seisman]

I am guessing we need to add a new modifier to -JP|p, e.g. +kkind, where kind may be x (longitude) or y (latitude). The default would just be degrees.

This makes more sense to me.

[zhong-yy]

Thanks for the post. I guess GMT cannot know what the angular measures are, so it will need to be told. It looks like it assumes these are always longitudes. I think we need to contemplate a situation where we can communicate to -JP the following

1. The angles are longitude: Formatting will be as for longitude.

2. The angles are latitude: Formatting will be as for latitude.

3. The angles are just angles: Formatting will be for angles with degree symbol only.

I am guessing we need to add a new modifier to -JP|p, e.g. +kkind, where kind may be x (longitude) or y (latitude). The default would just be degrees.

Alternatively, we use -f0x and -f0y instead to indicate the same information.

Other thoughts on this, @joa-quim, @meghanrjones and @seisman ?

Thank you for your quick reply. I'm looking forward to the new modifier. By the way, do you know how to enable the axis label for JP? In this example, I used -Bya+l"Depth (km)" and but "Depth (km)" didn't show.

[PaulWessel]

No such option at the moment. I am having a look.