Underlays
Custom full colour underlay images can be used with Sanchez via -u / --underlay, specifying the path to the target image.
Three equirectangular underlays from the NASA Visible Earth collection are included with Sanchez:
- 1km spatial resolution daytime
- 2km spatial resolution daytime
- 1km spatial resolution nighttime
This section details alternative underlays which may be used with Sanchez, or with companion tools.
Alternate underlays are published to a separate Sanchez underlays repository.
The day and night underlays bundled with Sanchez can be used by Xplanet to create composite day/night images. The underlays below were created by mlavespere to add better contrast between day and night.
To use, you will need to update your Xplanet configuration to use the night underlay, and replace the replace the earth.jpg and night.jpg in xplanet/images with the images below.
Note that Sanchez currently performs 2D blending of the underlay and satellite images and is therefore unable to accurately adjust the IR image for nighttime images. For full control, it is recommended that an equirectangular render is first created in Sanchez, and XPlanet used to create the 3D render using this as the image map.
Edit xplanet/config/default and add the following line to the [earth] section:
night_map=night.jpg
xplanet -body earth -projection rectangular -num_times 1 -geometry 10848x5424 -output underlay.jpg
If desired, a timestamp may be specified using -date YYYYMMDD.HHMMSS. See the Xplanet README for more details.
This combined day/night output underlay image may then be used by Sanchez using the -u / --underlay argument.