FIX: check whether -C and -E use different unit in grdtrack

[Dengda98]

bug description

1. In grdtrack module, -C and -E use different default units for geographic grids (meter for -C, kilometer for -E). Users might comfused about the result if they did't explicitly set units.

2. Also, it seems that -C and -E cannot use different units, even if I explicity set them. For example,

    $ gmt grdtrack -G@earth_relief_30m -C10d/0.1/5 -E125/33/146/46+i10k | head -n5
    > Cross profile number -L0-000 at  125.000/033.000 az=-45.1
    152.120545696   2.11440582896   -555983.596548  143.502762578   -4493.94584719
    -104.038158968  -52.8958698548  -544862.587853  143.502762578   -4172.34066777
    -15.7830363619  13.8917296377   -533750.674146  80.1535161628   25.4353068519
    104.739638124   45.5743008564   -522618.396532  37.7551090445   1373.92989473

   while the result seems fine if I set the same unit,

    $ gmt grdtrack -G@earth_relief_30m -C10d/0.1/5 -E125/33/146/46+i0.1d | head -n5
    > Cross profile number -L0-0 at  125.000/033.000 az=-45.1
    120.595820698   36.4509628442   -5.00004763636  132.358684312   36.0413484424
    120.687607339   36.3835507254   -4.90002198049  132.358684312   24.5587581626
    120.779234893   36.3160685085   -4.79999733063  132.413174504   11.9851527852
    120.870703862   36.2485164875   -4.69997368705  132.467483417   -0.153214879891

What's changed

Not perfect solution, I just add an if statement to check whether they are the different unit. After recompiling, same command above will return error,

$ gmt grdtrack -G@earth_relief_30m -C10d/0.1/5 -E125/33/146/46+i10k | head -n5
grdtrack [ERROR]: Option -C and -E shoule take the same unit, but received d (-C) and k (-E). Recommend you explicitly set the same unit for -C and -E.

[joa-quim]

Ideally we should allow to give different units in -C and -E, that is, to fix the bug. But I agree that at least we must prevent the bug. The situation is even worst since using the default units in -C (meters) and not specifying them also gives a wrong result.

C:\v>grdtrack -G@earth_relief_30m -C10k/0.1/5 -E125/33/146/46+i10k | head -n5
> Cross profile number -L0-000 at  125.000/033.000 az=-45.1
124.961987936   33.0317175099   -4.99879866781  134.848764621   -76.7744074835
124.962748445   33.0310832727   -4.89882247286  134.848764621   -76.7793602104
124.963508944   33.0304490308   -4.79884628695  134.849179173   -76.7842964579
124.964269431   33.0298147843   -4.69887011009  134.849593714   -76.7892161242

C:\v>grdtrack -G@earth_relief_30m -C10000/0.1/5 -E125/33/146/46+i10k | head -n5
> Cross profile number -L0-000 at  125.000/033.000 az=-45.1
67.725100627    53.4634275505   -5008.40682804  93.24866069     229.590712253
67.7266088084   53.463376577    -5008.3065395   93.24866069     229.699727907
67.7281169861   53.4633255845   -5008.20625097  93.2498724778   229.808730684
67.7296251602   53.463274573    -5008.10596244  93.2510842626   229.917719599

Could you please also add information to this limitation to the documentation?

[joa-quim]

Can you please rephrase this to:
"Sorry but a current limitation obliges that options -C and -E must have the same unit, but received %c (-C) and %c (-E). "
"You must explicitly set the same unit for -C and -E.\n", Ctrl->C.unit, Ctrl->E.unit);

[Dengda98]

Sorry for delay response. Maybe you can edit it later ?

[joa-quim]

No problem. I added it directly to master.