[OSM-talk] Determining direction of travel and segment connectivity from GPS traces

[Nick Black]

On 5/9/06, Lars Aronsson <lars at aronsson.se> wrote:
>
> Nick Hill wrote:
>
> > If we are thinking of creating a system which can determine
> > valid routes, we will need to determine valid routes for
> > specific modes of transport.
>
> Do it the Amazon.com way: People who have been here, traveling at
> your speed and direction, have later ended up there or there.



Yes, but I think the big issue that Nick is alluding to is the quality of
the data and its source.  We need substantial metadata to be able to use the
track data for routint - if it is to be reliable.  For example - we need to
know if the data has been collected from buses in bus lanes, from couriers
in vans or bicycles.  From the E-Courier data alone we could get data from
vans, cars, bikes and bicycles I think.

For every point and speed vector (within some margins), you need
> at least 10 observations in order to make an accurate prediction.
> You need a lot of track data, such as we have for Oslo and London.


I think we also need quality assesment of the tracks, maybe include DOP
values and covariance in the metadata to give an indication of the
reliability and accuracy of the data.  I like nick's ideas re filtering out
the crap data and averaging the good stuff.  Time of day would also be a
major factor.  I system like this could have the edge on other routing
systems as we would be able to continually asses journey time estimations
based on, as you point out, the current time for the particular time of day.



(A Swedish web bookstore tries to make recommendations without
> this threshold.  For many less common titles, it only gets
> ridiculous.  People who bought "Practices of an Agile Developer"
> also bought "The Concept of Anxiety" by Soren Kierkegaard,
> http://www.bokus.com/b/097451408X.html )


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