[postgis-users] Programmatically generate maps zoomed to extent of shapes?
jlpoole56 at gmail.com
Wed Sep 22 20:35:50 PDT 2010
I'm preparing walk lists for a campaign which contains a table of
addresses, about 35 to a page on 8.5" x 11" paper. I have the
addresses tied into a postgis database with roads and assessor's
parcels, so for a given page, I can get a handle on the IDs of the
What I'm wondering is would it be possible to generate a map in SVG or
PNG/TIFF that would measure 8" x 10.5" and be zoomed to a level that
would just include the most opposite parcels. I gather I could define
a shape that is all inclusive of the list of shapes for a particular
page, but can I then take the coordinates or whatever information
derived and submit it to a renderer which then creates a zoomed image
of defined dpi (if PNG or TIFF) that would be a representation of a
view of all parcels.
For example, I have a list of addresses, being 35 representing 3 1/2
200 Main Street
204 " "
535 " "
All of the above addresses tie into specific shape IDs in postgis.
I'd like to have a map which would then display a zoomed level so that
the parcel of 200 is leftmost and parcel 535 is rightmost of the
image. This map would be generated on the fly without human
intervention, in other words generated by script.
I'm getting my feet wet with various renderers, but have not seen any
that might be manipulated or controlled programmatically so that mapes
could be generated by scripting.
What I am envisioning is having a map of the parcels on the back side
of a previous page representing an view of the current page. So, if
page three (3) contains the above addresses, the back side of page two
(2)would have the map showing all parcels tied to the addresses of
page three. That way someone looking at the list on page three could
hold up the back side of page 2 in a binder and view a map zoomed to
the right level containing all the parcels referenced on page three.
I'd prefer to use my own data from postgis, I think this kind of
generation would be possible with the Google maps API and possibly
creating a container shape that bounds all the shapes from the list.
It would be helpful to learn of any renderers, especially ones that
expose an application interface.
(Hmmm.. now I'm thinking I could generate a large image file of
certain sectors and if I could tie the pixels, I could use ImageMagick
to slice and dice what I need.)
Any rate, this is a wild inquiry which might garner some attention and
generate some responses about renderers, especially ones with exposed
APIs so they can be manipulated programmatically.
John L. Poole
P.O. Box 6566
Napa, CA 94581-6566
jlpoole56 at gmail.com
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