Re: altitude reference system

hello martin.

> As far as this goes, the simplest approach is to pick one and stick to it.  The advantage of making the decision is that there is no guessing what a particular value means - you have a standard.  Admittedly, there is the drawback that when I say I'm at -60m altitude in Sri Lanka I'm not really underwater, but that's the compromise cost.

if you have flags indicating where an altitude comes from and what the 
value means, you also would have no guessing and a standard. i think we 
can agree that whatever the API will do, it has to be well-defined.

> This is not a question of better or more accurate results.  Providing a value based on the geoid (as opposed to the reference ellipsoid) is no more correct, it just matches better to user expectations.  What you are talking about is a user presentation nicety.

call it a nicety, but i think the fact that more and more GPS devices 
have that nicety built-in demonstrates that it seems to be one people 
want to have. so why force people who want to have that nicety to handle 
the EGM datasets, when these maybe built into their devices?

(i am also asking myself how likely it is that manufacturer who do care 
about the EGM nicety and have it built-in will actually do expose the 
non-nice value through the API, but i do admit that this is pure 
speculation.)

cheers,

dret.

Received on Monday, 5 January 2009 03:02:03 UTC