If the user sets a non-zero value of the delay it will be used in preference over the default value for that GPS type.
If the GPS type is unknown and the parameter is set to zero, then a default delay of 1 sample period will be used (eg 200ms for 5Hz).
Do not time out and provide an escalating series of messages. We may need to adjust the time thresholds used for escalation.
Do not wait if the EKF is not using the GPS.
Copter operation without a magnetometer is limited to constant position and relative position modes only (no GPS or range beacon fusion permitted)
Copter optical flow operation without a magnetometer is permitted.
The ability of planes to takeoff/launch without a magnetometer and align the yaw using the GPS velocity is retained.
Prevent bad values for GPS time delay pushing the GPS time stamp outside the range of IMU data contained in the buffer. If this occurs it can prevent the GPS measurements from being fused and cause loss of navigation.
Use the time delay returned by the GPS driver.
Wait long enough for the GPS configuration to be determined, but time out after 30 seconds and warn the user that a default value for time delay will be used.
Switch to use of an airspeed reading averaged across the raw sensor readings. since the last update.
This avoids use of the IIR which requires a larger time delay compensation and violates the assumption of uncorrelated noise.
The time delay parameter has been reduced to compensate for the removal of the airspeed IIR filtering.
This value is a compromise between what works best for a Ublox 6 which is around 200msec delay and the more recent 7 and 8 series receivers that are around 120msec delay.
Adapt the lengths of the IMU and observations buffers on startup to the specified time delays and update rates.
This does require the EKF to be re-started if time delays are changed.
priseborough
Andrew Tridgell
murata