[OSM-dev] Altitude data & (cycle) route profiles
MilesTogoe
miles.togoe at gmail.com
Mon Mar 31 16:51:11 BST 2008
Lambertus wrote:
> Robert Vollmert wrote:
>
>> 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.
>>
>>
> Those sensors need calibration against a known point and can give a huge
> offset when uncalibrated. I have such a GPS (GPSmap 60CSx) and never
> calibrate it as will most others presumably. As a cyclist all I'm
> interested in is the relative altitude differences not the precise
> actual altitude as opposed to, say, skydivers. Measuring relative
> altitudes is quite accurate (+/- few meters) though. The data is useless
> when you want to use it as a primary source, but it should be alright if
> you want to use it to determine offsets when compared with a known
> point. This requires you to process the GPX nodes trace-by-trace so you
> can determine the offset from which the trace started.
>
> I appose to using altitude data on nodes. E.g. one would not be able to
> move a node when that data is added without having to correct/remove the
> height data as well. Also adding altitude data invites to add
> -otherwise useless- nodes everywhere. I prefer to have altitude data
> kept apart from OSM database. Perhaps our own SRTM database
> corrected/enhanced using our traces.
>
maybe one idea for opposing viewpoints would be to have a separate table
of node elevations ie node_id, elevation I'm thinking in Rails code
that anyone wanting to use elevation could do a "has_one, belongs_to"
kind of simple relationship .
> _______________________________________________
> dev mailing list
> dev at openstreetmap.org
> http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/dev
>
>
More information about the dev
mailing list