[OSM-dev] Altitude data & (cycle) route profiles

Sjors Provoost sjors at sprovoost.nl
Mon Mar 31 15:18:23 BST 2008

On Mon, Mar 31, 2008 at 4:02 PM, Robert Vollmert
<rvollmert-lists at gmx.net> wrote:
>  On Mar 31, 2008, at 12:00, Andy Robinson (blackadder) wrote:
>  > Also as a civil engineer I can see some merit in having elevation
>  > data for
>  > physical objects in the database. However, we don't really have a
>  > good way
>  > of collecting data that is remotely accurate to the level at which
>  > it would
>  > be significantly useful. Non survey grade GPS just doesn't cut
>  > muster for
>  > height data so we should never rely upon that. Even the Ordnance
>  > Survey
>  > doesn't currently record height data from survey grade GPS.
>  Not sure how common they are, but there's some GPS units with built-in
>  barometer (Garmin Etrex Vista HCX at least). The data they provide
>  should be good enough to be useful.
>  Cheers
>  Robert
Is the problem with non survey grade GPS that they are just
inaccurate, or are they somehow biased? Are we talking about 1 meter,
10 meters or a 100 meters inaccuracy? Perhaps the average of of lot of
measurements at the same spot is more reliable?


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