Peter Hopfgartner wrote:
> Dear Micheal,
>
> are there any good reasons not to use a normal cartesian grid? I can no
> tremember any GIS software that can use haxagonal tiles as a raster.
What I'm doing at the moment - I input the width of the map, max/min
lon/lat - it calculates the height of the map needed for pixels for to
have the same pixel/kilometer ratio both north/south and east/west.
Another php function converts lat/lon coordinates to x/y coordinates
that are oriented like gd wants them:
function getsquarelocation($lon, $lat, $maxlon, $minlon, $maxlat,
$minlat, $width, $height) {
$x = $width * (($lon - $minlon) / ($maxlon - $minlon));
$y = $height * (($maxlat - $lat) / ($maxlat - $minlat));
return array("x"=>round($x),"y"=>round($y));
}
Obviously there's a little distortion but not much-
Sample data points in google earth:
http://homepage.mac.com/mpeters/misc/500flags.png
Same data points in my script:
http://homepage.mac.com/mpeters/misc/500flags2.png
They look like they have the same spacial relationship to me.
So I am using cartesian coordinates, I just feed the output of that
function to another function that finds the data points for the gd
imagefilledpolygon and the hexagons are created. I actually have the
hexagons overlap a tiny bit (2 pixels) to prevent a possible 1 pixel
space between them from rounding issues.
I think I may have found what I need - I found some articles on parsing
e00 files into arrays that I can then use to draw them with gd. Now the
only issue is the e00 files I have have *too* much information - they
are statewide - so I need to figure out which datasets in the files are
the ones I want ,,,
I may just write a shell script that parses the e00 file and turns the
data sets into php include files. There may be some scripts out there
that already do a similar thing I can steal, as e00 seems fairly common
and has been around awhile.
>
> Anyway, there is quite a lot of GIS software that you can obtain via
> EPEL [http://fedoraproject.org/wiki/EPEL].
>
> In case you want to publish geographical informations, do yourself a
> favor and use some of the many excellent tools out there, have a look at
> http://www.osgeo.org. A good part of the world's leading open source GIS
> people works on those projects.
>
> Some, trying to summarize: If you want to keep your data on a database,
> go with PostgreSQL and PostGIS or SQLLite with it's spatial extensions.
>
> If you want to work with desktop applications, have a look at QGIS and,
> at a more advanced level, GRASS.
>
> If you want to publish your data on the web and feel more inclibned to
> PHP then to JAVA have a look at MapServer for creating the rendered
> images of your geographical data and to OpenLayers or Mapbender or
> eventulally p-mapper for publishing the rendered images on the web.
> These are the tools that we been are using here for years and your can
> go any distance with them.
Thank you! I will look into those.
