Triton Isis User Manual

Page 86

June 2004 Isis® Sonar User's Manual, Volume 1

Speed is filtered according to the following formula:

1. Speed is forced to be between the min and max values as set by the

user.

2. Speed is smoothed by taking 90 percent of the previous speed and 10

percent of the new (just received) speed.

3. The amount of time that has elapsed between speed updates is

computed. If the amount of time is greater than 0 seconds and less than
60 seconds, then speed is further adjusted as follows:

• Acceleration = (new speed - previous speed) / (time difference)
• Adjustment = Acceleration / 2
• NewSpeed = NewSpeed + Adjustment

This has the effect of predicting speed based on the observed
acceleration. Speed is predicted by extrapolating between the current
update and the next expected update, assuming that updates occur
sequential in time.

4. The speed is checked again to verify that it is between the min and max

allowable range.

Navigation latency

(text box)

— If you know the amount in time, in

milliseconds, that it takes to get navigation data from your navigation receiver to
Isis, you can compensate for this lag time by specifying the latency here, in
milliseconds.

Test

(button)

— Clicking Test displays a window indicating which COM ports, if

any, have been allocated for use. (MMF is the ASCII-only serial data being
passed to Isis via a memory-mapped file.)

Chapter4: Setting Up Isis to Record Data