Vessel info PDF is incomplete

[wschildbach]

The [vessel info PDF](http://wiki.openseamap.org/images/0/0f/Vessel_info_de.pdf is not complete) is lacking some information.

1. What is the length? We suggest this would be the LOL (Schiffslänge).
2. It is not clear how the measurement/calibration of the depth sensor translates into "depth measurement" and "offset to keel"
3. The pdf suggests that it is necessary to measure the offset between GPS and depth sensor. The "add vessel" page asks for centerline offset of these separately.
4. Just for completeness, it would be nice if all measured values appear in the diagram.
5. If the page had fields into which I can enter the measurements, it would make it even more straightforward to translate that into the web page.

[cleanerx]

3. The total distance is not the right thing to use since for an advanced filter the boats orientation is relevant for physical movement and not the movement of course over ground.

[wschildbach]

So I understand what you are saying is that we need "absolute" positions of the sensors, rather than relative data?

In that case, I think we also need to mention the reference point for the absolute data, which presumably is the center of mass, correct?

[cleanerx]

To some point yes to some point no. For calculations that are relevant to mass like wind drift this is the right spot but in terms of steering it is the axis of the rudder and to some extent the keel that define steering angles. In any case a common user is probably unable to give such detailed information. So a good axis is the stern. Given the size and weight of the vessel one might roughly estimate the physics which should be sufficient to do further calculations.