Remote Data Set - Global Earth Day/Night Images

Q&A
1

I’m using grdimage and the remote Global Earth Image dataset to plot a background image of the west Pacific Ocean:

gmt grdimage @earth_day_03m -JM10c -R120/160/-10/40 -Ba5g5

When the command is executed I get the following message:

grdimage [WARNING]: The image memory layout (TRP ) is of a wrong type. It should be BRPa.

Despite the warning, the image is plotted correctly. Is the error message because I have done something wrong or is it a problem in the remote data set?

Also there is a mismatch between the image examples in the GMT documentation of the Blue Marble dataset and the actual remote data set. All the examples show ocean bathymetry, yet the actual remote dataset does not contain bathymetry, only ‘Land Surface, Shallow Water and Shaded Topography’. Are there plans to update the remote dataset to include bathymetry?

2

You are OK, that is just an internal message we now have hidden away more.

3

Do you mean that you could see the features of the ocean in the Day/Nigth images? This can be done by using the earth relief grid to generate a shadow in the satellite image.

4

As the caption says, “The above example mixes both images according to a day-night mask and adds illumination from a corresponding Earth DEM.”

5

Thanks Paul and Esteban. I didn’t realise that the ocean floor ‘structure’ was added later, I thought it was part of the remote Blue Marble image. Using Example Gallery 52 as my guide I have it all sorted now. For the benefit of others these are the commands:

gmt grdgradient @earth_relief_03m -Nt0.5 -A45 -Gintens.grd
gmt grdmix @earth_day_03m -Iintens.grd -Gbluemarble.tif
gmt grdimage bluemarble.tif -JM10c -R120/160/-10/40 -Ba5g5

Thanks again.