[GRASS-user] GRASS Network for Fire-station

[Moritz Lennert]

On 07/06/07 07:16, RAVI KUMAR wrote:
> Hi All,
> In GRASS Net-work analysis please help me build a
> network of fire stations (for demonstration) in an
> urban area such that the entire city is covered within
> a 5 minutes reaction time.
> 
> The SCHEME:
> 1. The existing fire stations are located as point
> data, on the existing urban-roads dataset for the
> city.
> 2. The distance that can be covered in 5 minutes by
> the fire-tenders will be plotted from each location of
> the fire tender. The distance is not as a crow flies
> but, on the existing roads.
> 3. This will show wide gaps in the urban sprawl where
> a fire tender cannot reach within 5 minutes, thus a
> scope for locating new fire tender stations such that
> any fire accident is within 5 minutes from
> fire-tender.
> 
> Present GRASS Networking:
> 1. v.net.iso must do the trick by making patches with
> distance that can be traveled in 5 minutes, I believe.

Yes, v.net.iso is precisely what you need.

If you need time distance you have to allocate time costs to the network 
first. You can create a column cost in your road map's attribute table 
(v.db.addcol) and thus assign costs to roads which you can then 
integrate into the v.net.iso calculations using the 'afcolumn' (and 
abcolumn if you work in two directions) option.

> 
> Please let me know any existing examples.

There is an example in the v.net.iso man page which should get you 
going. You can also check the initial introduction by Radim which is 
more detailed, but some elements are obsolete (such as using openoffice 
to add a new column):
http://grass.itc.it/grass57/tutorial/network.html

If these two are not enough, please tell us what precisely you need help 
with.

Moritz