Multi level modeling and loop closing with GridTiles

The objective of this paper is to use GridTiles to model a complex multi level scenario and additionally use the resulting model to help solving the loop closing problem. The GridTile algorithm is a memory and computational efficent method to map an unbounded outdoor environment of a human driven car. GridTiles are a set of small occupancy grids with a neighbourhood relation in the four directions. This paper discusses four of the major problems in modelling: the local and the global mapping, multi level modelling and loop closing. For each of these problems possible solutions will be shown. Local and global maps can be directly modelled with the standard GridTile algorithm. Because the neighbourhood of the tiles is only known locally, multi level scenarios can be modelled implicitly. Additionally a loop closing solution is proposed to correct the built model afterwards in a memory efficient way. Instead of the classic approach that has to store all measurements over an unpredictable duration, the GridTiles are used as a data storage.