> Ivan - There has been considerable discussion on uncertainty in this
> group. You may wish to read relevant emails and documents.
> That said, in geodesy a simple approach (and one that is often used),
> positional and local uncertainty become simple indicators of the
> quality of position. Positional uncertainty is global or absolute,
> computed with respect to the reference frame or datum. Local
> uncertainty is computed with respect to adjacent features within the
> same data set or source.
> There are many excellent references on uncertainty and geodetic
> coordinates. Just google "geodesy uncertainty".
Thanks. I'll try to grep over these references.
Unfortunately, this mailing list seems to bypass the Gmane
archive, which makes it a bit hard for me to fetch all the
postings at once for a later grep(1) invocation (and there's no
grep(1) for either HTTP or NNTP.)
> The point is that this group - in coordination with others such as
> the OGC - has invested considerable time discussing uncertainty and
> how to express such information within the context of the
> requirements as defined by this community. As such, how uncertainty
> is viewed and expressed is different than in the traditional GIS
> industry (where uncertainty is often ignored!) which is mapping
> uncertainty and not uncertainty related to an observation and
> measurement (as in sensors).
As I've pointed before, there may be different sources of
uncertainty, e. g.:
* the uncertainty associated with the measurement method used;
(and doesn't it become the mapping uncertainty whenever one
uses a map to determine the coordinates of an object?);
* the size of the object, which location is being measured;
* the mobility of the object; (but note that the intended
longevity of the geo: URI in question should be considered for
the mobile objects);
* privacy considerations.
Consider, e. g., that one may want to disclose his own location
so that it could be related right down to the continent, country
and the city, but not to the street, building, floor and room.
Even if the measurement done with GPS would give uncertainty
level closer to the latter, the publisher of the information may
still deliberately opt for a higher uncertainty.
> Happy to discuss more if you like :-)
[...]
--
FSF associate member #7257
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