[Qgis-developer] Fleet Management Tools

[Petros Apotsos]

Wow,
a most prompt and to-the-point response!! I have absolutely no experience with PostGIS, but it was already in my priorities list, so I will get to it and post back with results and/or comments.
I have to say I disagree with some points of your answers, but I have to do some work first, before posting a formal reply.
Thank you again for your prompt and concise reply,


Petros Apotsos

Rural & Surveying Engineer
Technical Chamber of Greece Registry Number 96798
Τ: 2310 220345
F: 2310 220346
Ermou 18A, Postal Code 54624
Thessaloniki, GREECE



Hello,

> Given a Point Cloud (either a file or a stream) that represents 
> positions, speed and direction of a vehicle fleet (TAXIs in my case), 
> and a graph (geometric network) that represents roads and 
> intersections, I want to be able to do the following:

Your problem will probably be best answered through PostGIS queries, which you can then visualize with QGIS, and/or a custom web-based application.

Let's say you have a table taxi_position like this, where position is a point geometry :

| gid | taxi_id | speed | pos_time | position |

> 	1. Track down the route of any single vehicle, as a succession of 
> points on the network.

Group by taxi_id, order by pos_time and make a line with the resulting points.

> 	2. Calculate the total passes of vehicles through any given point or 
> segment of the network.

Join your segment (or node) network with your taxi_position table, allowing a tolerance around the segment/node (st_dwithin will do the trick), then group by taxi if you want to consider each vehicle only once.

> 	3. (Not as urgent as the above) Find the nearest TAXI to a random 
> point on the network.

With PostGIS > 2.0, use KNN-search to do it fast as light. Otherwise, use st_dwithin with growing values for the search radius.

> All of the above need to be FOSS-based solutions.
check.

> Although I am willing and ready to program plugins or algorithms to do 
> the above tasks, I am not really into re-inventing the wheel, so my 
> questions are the following:
> 	A) Are there any libraries or plugins that handle the above tasks?
> Is there any FOSS work already done with them?

That would be a few SQL queries then.

> 	B) Is QGIS ready (aka efficient enough) to handle those tasks, or 
> shall we try other tools/software?
Use QGIS as visualization tool, and PostGIS as a backend, and you're set for hundred of millions of positions without problem (well, do not visualize everything at once).

> Any opinions on my task would be greatly appreciated!
You're welcome

Vincent

> Thanx in advance!
> 
> Petros Apotsos
> 
> Rural & Surveying Engineer
> Technical Chamber of Greece Registry Number 96798
> Τ: 2310 220345
> F: 2310 220346
> Ermou 18A, Postal Code 54624
> Thessaloniki, GREECE
> 
> 
> 
> 
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