
5.1 Sensors
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directions, which are not always orthogonal to each other. If the
robot is facing north and wants to go west, it might turn more or
less than 90 degrees (the compass is not linked with the wheel
encoders). In general, the readings provided by our compass are
locally consistent to about 3 bits, and globally consistent to 2
bits.
That is, the compass never deviates more than 45 degrees
from the true direction over our test area, although the region
qualitatively marked as "north" may vary in angular width.
Some of the more pronounced shifts can be explained by the
proximity of objects with high iron content (stippled regions i ...