[OSGeo Africa] Travel Time Calculation

[Uazukuani]

Hi Gavin

I am under strict instructions to calculate along the road network. It is
for the Census of Agriculture. I have to calculate the travel time from
each village to the nearest urban center "by motorable road" to have a feel
of how long (far) farmers have to travel to get fertilizers, pesticides,
seeds etc.

*It is possible to calculate the closest along the network but that is a
bit more complicated and straight line distance might be good enough.*

I noted that pgRouting is well documented and will definitely give it a
try, but since I have to calculate along the road network and have no prior
experience of pgRouting, are you still recommending it?

rgds,
Uazu


On Mon, Jan 14, 2013 at 8:07 PM, Gavin Fleming <gavin at afrispatial.co.za>wrote:

> Hi Uazu
>
> I would use pgRouting (http://pgrouting.org/)
>
> - install pgRouting
> - add pgRouting to a PostGIS database
> - load your roads and points into the database
> - set up network topology by adding nodes with the assign_vertex_id()
> function. Check that you have a properly connected network.
> - you can use any value as cost. In this case you'd want to calculate the
> cost field (pgRouting uses 'length' be default) as travel time. You could
> use road length with other information like speed limits to calculate or
> estimate travel time per road segment.
> - Set up lists or tables of your villages and urban centres
> - Use PostGIS functions to calculate the closest urban centre to each
> village (as the crow flies). It is possible to calculate the closest along
> the network but that is a bit more complicated and straight line distance
> might be good enough.
> - Then use pgRouting to calculate the shortest path between each of your
> chosen pairs and return travel time.
>
> To automate this I would write a Python script.
>
> There is good documentation and workshops on the pgRouting site and
> elsewhere.
>
> hth
>
> Gavin
>
>
> On 14/01/2013 16:20, Uazukuani wrote:
>
>> Dear All
>>
>>
>> I have a problem that I hope someone on this mailing list could assist
>> with.
>>
>> I want to calculate travel time from (each) VILLAGE to the nearest URBAN
>> CENTER along the road network*.*
>>
>>
>> The output format could be text or GIS with at least 3 columns: 1.
>> Village, 2. Nearest Urban Centre and 3. Travel Time.
>>
>>
>> I have 3 data sets: 1. Villages (Point), 2. Urban centers (Point) & 3.
>> Roads (Polyline/line) for the whole country (Namibia).
>>
>>
>> I would appreciate if someone refers me to tutorials on this.
>>
>> I have access to PostGIS, QGIS and GvSIG, ArcInfo, GeoMedia Pro 6.x, MS
>> SQL Server 2008 (Spatial) but am willing to try something else.
>>
>>
>> Rgds,
>>
>> Uazu
>>
>>
>>
>>
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>>
>
>
> --
> regards
>
> Gavin
>
> Gavin Fleming
> http://afrispatial.co.za
> t: 0218620670
> c: 0845965680
> f: 0866164820
>
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