Handling Altitude=Depth mode

[ejalaa12]

Hi,

On the ROVINS, there are two modes for handling the altitude: depth and GPS.
In the GPS mode, the altitude of the gps (distance to ellipsoid/geoid) is filtered to obtain the altitude. The filtered altitude value is what we would expect: the vertical distance to the ellipsoid.
However, in the Depth mode, the depth is used to estimated the altitude, however this is incorrect as the depth is the vertical distance from the INS to the water surface (which moves with time!)
Unfortunately, the issue is that the published NavSatFix contains incorrect data, and can't even be projected correctly to other systems (ECEF, UTM ... etc) as the altitude value is in fact the depth.

Do you have any idea on how to solve that issue?

Propositions/Ideas:

• add int8 ALT_REF_WATER_SURFACE=2 in the Ins.msg file, and set the reference to water_surface when the rovins is in DEPTH mode.
• Allow an offset (=water surface altitude) to be added (through a topic) to correct the altitude