MILS: Modular Integrated Landscaping System. This standard has been developed by members of the HispaLUG/HispaBrick community for collaborative diorama displays. Among its key features is that it is simple and flexible and can be used with many different LEGO® themes besides trains.
The MILS standard is primarily based on 32x32 baseplates; however, intermediate sizes of 16x32 can be used as long as its terrain features share a common profile with adjacent modules. Ground level is 1 brick (3 plates) above the baseplate reference level. Modules interconnect with Technic pins into 1x4 Technic bricks located at module corners. Typically the 2x2 corner space is used as an identification feature. This identification can be used by a builder to show ownership or it can be used as guide for orientation between adjacent modules.
MILS Basic Terrain Modules (BTM)
MILS BTM modules have so-called "null" profile, i.e. no contours at the edges.
MILS BTM with Roads
MILS BTM with Water Features
Water features are rendered at 2 plates above the baseplate. The bottom layer is typically blue or green colour plates with a top layer of transparent tiles, often using dark transparent blue.
MILS Contour Terrain Modules (CTM)
MILS contours are specified as either a "Short Profile" or "Long Profile". Short Profile contours are nominally 1 plate per stud gradient whereas Long Profile contours are 1 plate per 2 stud gradient. So-called "null" profiles are at ground level whereas "Full Profiles" are 5 bricks (15 plates) above ground level.
For additional information on MILS, please refer to these links: