Surface Tiles are a way to use high resolution ground textures for a small local region, usually around a base.
The earth is split into 2048 tiles in latitude and 4096 tiles in longitude.
The surface tiles in orbiter consist of two parts: The actual tile textures for the planet and the surface tile definition in the configuration file of a base.
Configuration file syntax
The syntax for a surface tile list is
BEGIN_SURFTILELIST <texturelevel> <tilenumberfrommeridian_positive_for_east> <tilenumberfromequator_positive_north> <bitflag_for_transparency> END_SURFTILELIST
The filenames for the textures follow a similar scheme:
<planet name>_<texture level>_<E/W><tile number in latitude>_<N/S><tile number in longitude>.dds
The function for getting the tilenumber in latitude is:
TN_lat = 1024.0 * latitude / 90.0
The function for getting the tilenumber in longitude is:
TN_long = 2048.0 * longitude / 180.0
Each surface tile is roughly 5 x 5 km large.
The transparency bitflag is usually 1. If the tile contains transparency in the alpha channel, the bitflag has to be changed to 3
It is planned for future versions, to replace the surface tiles by a ultra high resolution planet texture (Level 15?).