GMT downloads dataset twice

Q&A
1

Assuming the dataset is not already downloaded/run gmt clear data.

Simple script:

res=@earth_relief_05m
proj=-JS0/90/50c
r=-R0/60/70/90

gmt begin map png
echo "Running grdimage command.."
gmt grdimage ${res} ${proj} ${r} -Bafg

echo "Running grdcut command.."
gmt grdcut ${res} ${r} -Gtemp-slope.nc
gmt end

When executed, the dataset is downloaded twice - one time for each command:

Running grdimage command..
grdblend [NOTICE]: Remote data courtesy of GMT data server oceania [http://oceania.generic-mapping-tools.org]

grdblend [NOTICE]: SRTM15 Earth Relief at 05x05 arc minutes reduced by Gaussian Cartesian filtering (9.3 km fullwidth) [Tozer et al., 2019].
grdblend [NOTICE]:   -> Download 180x180 degree grid tile (earth_relief_05m_p): S90E000


Running grdcut command..
gmt [WARNING]: Remote dataset given to a data processing module but no registration was specified - default to gridline registration (if available)
grdblend [NOTICE]: Remote data courtesy of GMT data server oceania [http://oceania.generic-mapping-tools.org]

grdblend [NOTICE]: SRTM15 Earth Relief at 05x05 arc minutes reduced by Gaussian Cartesian filtering (9.3 km fullwidth) [Tozer et al., 2019].
grdblend [NOTICE]:   -> Download 180x180 degree grid tile (earth_relief_05m_g): S90E000

Should not this be done only once? Note exact same -J and -R.

Re-run the script again - and both commands understand that the dataset is already available and no download is initiated:

Running grdimage command..
Running grdcut command..
gmt [WARNING]: Remote dataset given to a data processing module but no registration was specified - default to gridline registration (if available)

I tried executing the grdcut command first, to see if that made any difference, but no - it still downloads twice.

I forgot to add $proj to the grdcut command. Adding that still does not stop the double download. Not that it should matter, but you never know.

2

Maybe @Joaquim could have a look to see what happens - I am on a road trip this weekend,

3

What I want to get rid is of this warning (at this -V level). It’s a pain and I bet most users will not understand it.

4

And why does this warning only show with the grdcut command, and not the grdimage command?

5

Grdcut assumes you know what you are doing while grdimage just wants to plot whatever and we have a default registration- cannot have that for data processing.

6

That makes sense.