Gmt 6 solar module colour fill flipped

Q&A
1

Good afternoon gents, I have two questions:

  1. I am trying to plot daylight and twilight on a particular date and time in the UK. It’s late in the afternoon so it should be light in the west (sun is setting) and dark in the east.
    When my underlying map is something geographic like Hammer it plots just fine. When I try to plot something more local (using -JH for example) I get the shading on the OPPOSITE side of the line!! In other words, I get the dark navy colours west of the line, closer to the sun.

  2. On a separate note, not sure how to adjust for timezones. Trying to play with different timezones and appending +z3 or +zTZ3 makes no difference to the shading. I’m pretty sure I’ve got the +z syntax wrong.

This will produce a map with “wrong” shading:

gmt begin test
gmt coast -JT0/30c -R-15/15/50/60 -Dh -W -Bafg -A500 -Gdarkgreen
#gmt coast -JH0/30c -Rg -Dh -W -Bafg -A500 -Gtan
gmt solar -Td+d2020-11-04T16:30:00 -Gnavy@80
gmt solar -Tc+d2020-11-04T16:30:00 -Gnavy@70
#gmt solar -Tn+d2020-11-04T16:45:00+zTZ+3 -Gnavy@85
#gmt solar -Ta+d2020-11-04T16:45:00+zTZ+3 -Gnavy@80
gmt end show

2

Gents, bumping this because I genuinely think it might be a bug. When -Rg is used, results are normal, when -Rxmin/xmax/ymin/ymax is used, results are flipped.

3

I suspect this is another issue with wrapping polygons around the Earth. Can you please open an issue with this.

Regarding the time zones, it’s working for me

gmt pssolar -I-7.93/37.079+z0
Sun current position:
        Longitude = -128.578379
        Latitude  = -22.616270
        Azimuth   = 273.1928
        Elevation = -43.7170

        Sunrise   = 07:32
        Sunset    = 17:14
        Noon      = 12:23
        Duration  = 09:43

gmt pssolar -I-7.93/37.079+z1
Sun current position:
        Longitude = -113.640860
        Latitude  = -22.616289
        Azimuth   = 264.3525
        Elevation = -31.8148

        Sunrise   = 08:32
        Sunset    = 18:14
        Noon      = 13:23
        Duration  = 09:43