Product Manual

This chart deserves a few more comments and explanations:

• Accuracy has a linear relationship to baseline length.

However a too long baseline length can result in

differential multipath between antennas and introduction

of vehicle flexing into the heading solution. These two

factors are detrimental to heading accuracy. In addition,

the longer the baseline length, the longer the calibration

sequence. That’s why baseline lengths of three to five

meters are recommended. Baseline lengths less than one

meter are not advised.

• Accuracy figures given above are 1-sigma values, or RMS,

which means that 67% of the measurements are at or

below these figures.

• Heading accuracy will be about a factor of 2 better than

pitch or roll accuracy. Pitch and roll accuracies are the

same.

• In each figure, the lower line (blue) represents accuracy

achievable if no multipath errors were present. In a normal

environment, this is not possible. Multipath effects from

typical environments are depicted by the upper line (red).

For a given baseline length, the performance of the

SP90m should lie somewhere near the upper line.

• A moving vehicle does not experience as many multipath

effects as when it is stationary. This is because multipath

is a correlated error. Correlated errors become more noise-

like under vehicle dynamics and therefore can be filtered

out. Therefore, accuracy results improve toward the lower

line (blue) when the vehicle is moving.

Elevation Offset

Ideally, the two antennas should be installed at the same

elevation. You may however be facing some installation

constraints on your vehicle compelling you to install the

antennas at different elevations. If that is the case, this is

0.1

0.01

0.001

10 100 1000

Baseline Length (m)

Heading Accuracy (°)