.. _odometer:

Odometer
========

The odometer is a sensor that measures the rotation of the wheels of the robot.
From the number of rotation of each wheel it can calculate the distance the 
robot has driven, the direction it is facing, and even the location the robot
has reached by doing this. Unfortunately like all sensors there is a bit of 
noise in the measurements. This noise originates from 3 main sources:
Encoder errors from sensor resolution, error in the wheel radius, and a 
calculation error. The noise in the measurements is 0.005m, and does not sound
like much, however, there is a catch. Because the position is calculated from 
consecutive measurements the noise becomes a cummelative error. This means that
the more distance you drive, the bigger the error becomes, and the less certain 
you are that the position the odometer indicates is actually the position the 
robot is in. 

Another problem of the odometer is that it is based solely on the rotation of
the wheels, and as such, it can not cope with a situation where the robot is 
stuck but the wheels still turn. This results in the position being completely
wrong. 

However as long as you dont drive into anything the odometer is quite a 
reliable and reasonably accurate way to find our position. For example: after
driving around the arena, the error had added up to about 0,5m.



.. automodule:: odometry
    :members: