The odometry error of a mobile robot contains both sys- tematic and non-systematic components. The first ones are independent of the environment while the second ones depend on the interaction of the robot with the environ- ment where the robot moves. In this paper the odometry error of a mobile robot with a synchronous drive system is modeled by introducing four parameters characterizing its systematic and non- systematic components (translational and rotational). Some experimentally measurable quantities, called ob- servables, are introduced for a given robot motion. On the basis of the odometry error model the average values and the variances of the observables are analytically com- puted. These quantities depend on the previous model parameters and on the considered robot motion. A strat- egy in order to simultaneously estimate the model pa- rameters by estimating the observables is suggested. This strategy only requires to measure the change in the ori- entation and in the position between the initial and the final configuration of the robot related to suitable robot motions. In other words it is unnecessary to know the ac- tual path followed by the robot. The proposed strategy is illustrated by discussing the accuracy on the parameters estimation both in an indoor and outdoor environment.