The terrain offset solution status is usable for a short period of time without state updates so a timeout has been added which prevents the rapid changes in solution status due to short duration sensor read errors.
this will be used in plane to make AHRS SYS_STATUS unhealthy if a user
tries to fly with EKF enabled without a full 3D accel cal.
Note that it doesn't rely on using AP_Param load() to detect that a
value has been set, as some users are first doing a 3D cal then later
doing a 1D cal. In that case load() was returning true and would give
a false positive
to ensure the GCS knows that we have lost the GPS we need to keep
reporting GPS_RAW_INT messages when the GPS disappears. Sending at 1Hz
should be sufficient
Fixes issue #1722
This fixes a bug which could have caused the realative position status to be incorrectly reported under some conditions and also caused a compiler warning message. the logic used to report the filter solution status has been broken down into smaller, easier to understand statements.
Non user adjustable parameters are now declared as 'const' in the header.
The _ prefix has been removed from non user adjustable tuning parameters.
We use a function call rather than a constructor to initialise variables because it enables the filter to be re-started in flight if necessary.
For consistency some signed integer type declarations have been changed to unsigned where appropriate.
The decision to switch to constant velocity mode during optical flow operation and te decision to switch back were previously being made in two different places in code. Both decisions are now made in the one place which makes the code easier to follow and maintain.
Move velocity store out of optical flow to velocity and position fusion control as it is a velocity fusion function.
Always clear the previous mode status
This patch makes the reporting of an absolute position solution less abbiguaous and ensures that relative position is always true if absolute position is true
