[mapserver-dev] RFC-108 : heatmap generation

Basques, Bob (CI-StPaul) bob.basques at ci.stpaul.mn.us
Thu Jan 30 14:18:15 PST 2014

Hmm, depends on the business need, I have one report related to usage of road intersections, or crossing trails (still points albeit) that are the result of crossing lines.  Also trails that cross and coincide with each other for a while might be better served using a line feature, especially where the lines get longer.  

Additional info: We have a mixed GPS collection system. We get some data via radio which is less frequent that what is coming from Cell data connections.  Upwards of 15 sec spacing for the radio connections, the cell data can get down to less than a second for example.  Those longer timespans got me on the usage of Lines for the features to cluster by.

No worries here, I just did some SQL from the database that sent back some prorated points along the lines.  I'll need to figure out a nice median time spacing is all.


-----Original Message-----
From: thomas bonfort [mailto:thomas.bonfort at gmail.com] 
Sent: Thursday, January 30, 2014 3:52 PM
To: Basques, Bob (CI-StPaul)
Cc: mapserver-dev at osgeo.org
Subject: Re: [mapserver-dev] RFC-108 : heatmap generation

Just a side note related to the specifics of your gpx requirements...
your actual input data is the sample points, not the lines that link the points one to another. From an information theory point of view, I believe that a heatmap created just from the gpx sample points will be more accurate than a heatmap that assumes that each point is connected to its neighbour by a straight line. Of course this only holds if your gps samples points at regular time intervals, i.e. does not apply some kind of simplification to suppress points along a straight line.


On 30 January 2014 22:12, Basques, Bob (CI-StPaul) <bob.basques at ci.stpaul.mn.us> wrote:
> Thomas,
> Just one suggestion related to features used for clustering, can you consider using LINE features as well.  My particular need could use points as described and probably still work nicely.  My specific need is for applying heat mapping to trail (GPS, Average Daily Traffic) lines, these lines are generated from points sequences though, so this would still be doable as RFC describes.
> There are occasional instances where long segments are introduced into the GPS data collections where a GPS lock goes missing for a while, these long lines are the things I would like incuded in a heatmap output.  Maybe there is a way to interpolate some points along a line that would still work with the scribed system as another mode of processing.
> Good stuff all around either way.
> History trivia, ask Steve L. sometime, about some heat-map work we did more than ten years ago now for an online mapping interface.
> Bobb
> -----Original Message-----
> From: mapserver-dev-bounces at lists.osgeo.org 
> [mailto:mapserver-dev-bounces at lists.osgeo.org] On Behalf Of Thomas 
> Bonfort
> Sent: Thursday, January 30, 2014 10:58 AM
> To: mapserver-dev at osgeo.org
> Subject: [mapserver-dev] RFC-108 : heatmap generation
> Devs,
> please have a look at RFC-108 [1]. The associated code and the RFC are still beta, so there's still plenty of room for modification or remarks.
> best regards,
> thomas
> [1] http://mapserver.org/development/rfc/ms-rfc-108.html
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