Mapping, localization, and navigation systems for use with a mobile unit are provided that use a sensor model with adjustable parameters. The system includes range sensors configured to collect range data and a data storage system having stored therein an evidence grid representing an environment and a sensor model comprising adjustable parameters representing inaccuracies of the range sensors. A grid engine adjusts the adjustable parameters based on received range data from the range sensors. A navigation module can direct the mobile unit though the environment using the evidence grid, received range data, and adjustable parameters. The grid engine can also locate the mobile unit within the environment by using the adjusted sensor model parameters to compare the received range data against the evidence grid.