NASA Global Earth Day/Night Images
We serve two NASA image products: The Blue and Black marble mosaics. We have filtered and down-ampled those as well at the same resolutions that are available for the Earth DEMs. However, all images are pixel-registered only. These images may be plotted with grdimage or grdview and manipulated by grdmix. The above example mixes both images according to a day-night mask and adds illumination from a corresponding Earth DEM.
Usage - Global Earth Day/Night Images
You access a global daytime image by specifying the special names
@earth_day_[rru]
Similarly for the nighttime view:
@earth_night_[rru]
The following codes for rru and the optional reg are supported (dimensions are listed for pixel-registered grids; gridline-registered grids increment dimensions by one):
Code |
Dimensions |
Size |
Description |
|---|---|---|---|
01d |
360 x 180 |
128 KB |
1 arc degree image view (Blue|Black Marble mosaic @ 111 km) |
30m |
720 x 360 |
435 KB |
30 arc minute image view (Blue|Black Marble mosaic @ 55 km) |
20m |
1080 x 540 |
918 KB |
20 arc minute image view (Blue|Black Marble mosaic @ 37 km) |
15m |
1440 x 720 |
1.6 MB |
15 arc minute image view (Blue|Black Marble mosaic @ 28 km) |
10m |
2160 x 1080 |
3.4 MB |
10 arc minute image view (Blue|Black Marble mosaic @ 18 km) |
06m |
3600 x 1800 |
8.8 MB |
6 arc minute image view (Blue|Black Marble mosaic @ 10 km) |
05m |
4320 x 2160 |
13 MB |
5 arc minute image view (Blue|Black Marble mosaic @ 9 km) |
04m |
5400 x 2700 |
19 MB |
4 arc minute image view (Blue|Black Marble mosaic @ 7.5 km) |
03m |
7200 x 3600 |
33 MB |
3 arc minute image view (Blue|Black Marble mosaic @ 5.6 km) |
02m |
10800 x 5400 |
71 MB |
2 arc minute image view (Blue|Black Marble mosaic @ 3.7 km) |
01m |
21600 x 10800 |
258 MB |
1 arc minute image view (Blue|Black Marble mosaic @ 1.9 km) |
30s |
43200 x 21600 |
935 MB |
30 arc second image view (Blue|Black Marble mosaic original) |
See GMT remote dataset usage for when resolution codes are optional or required.
All of these images will, when downloaded, be placed in your ~/.gmt/server director under
the earth/earth_day and earth/earth_night sub-directories.
Technical Information - Global Earth Day/Night Images
The 01m and lower resolution images are derivatives of NASA’s Blue and Black marble image mosaics. We have downsampled them via Cartesian Gaussian filtering to prevent aliasing while preserving the latitude-dependent resolution in the original images. The full (6 sigma) filter-widths are indicated in parenthesis. The dimensions above reflect the number of nodes covered by the global images and the sizes refer to the geotiff files on the remote server. Note: This data set is experimental and the format and delivery is likely to change in the future (e.g., via image tiles). To make the files as small as possible we have also downgraded them from 24-bit to 8-bit indexed images.