On Apr 29, 5:39 pm, Dommer <[email protected]> wrote:
> I've been building a map to display impervious surface polygons:
>
> http://freeforthepicking.com/imagery/kmlmap4.php?q=1101850&Submit=Search
>
> My polygons were converted from arcview shp files using shp2mysql into
> Geometry entries in a MySQL geodatabase. From there, the shapes are
> called by php and dumped into a KML file based on user-entered
> information, and then that KML is displayed as an overlay.
>
> Okay, so: the polygons in Arcview and the polygons displayed in my
> maps view are different, the ones in the API are simplified: vertexes
> missing etc. So, I check the KML file, and it looks good: the
> polygons when displayed in google earth look fine. So, I deduce that
> the polygons MUST be being simplified when the coordinates information
> is taken into Google Maps.
>
> Between the two sets of polygons, the smallish polygon on the right
> building is rectangular in before (arcview), but that same polygon in
> after (google maps) is distorted in its upper righthand corner.
> Similarly, the polygon for the main building in before has sharp
> corners and is mutually exclusive with the polygon for the parking lot
> - whereas in the google maps version it is a misshapen tetragon that
> overlaps with the parking lot polygon in the lower left side.
>
> My question is: why, how, and what can I do to abrogate this
> simplification (if anything).
>
> Below are links to the before and after information for the above
> polygons as well as a link to the KML file which shows the coordinates
> and is getting mistranslated/interpreted above.
>
> Thank you to anyone how can provide insight into this challenge:
>
> Before:http://freeforthepicking.com/imagery/before.jpg
>
> After:http://freeforthepicking.com/imagery/after.jpg
>
> KML:http://freeforthepicking.com/imagery/KMLs/1101850isu.kml
>
> Yours Gratefully,
>
> Dominic
If you can force GGeoXml to use "mapslt", the successor to "mapsdt",
it will build a fast & accurate tile layer overlay for you. If your
KML file contains only polygons & polylines, it can be converted to a
tile layer overlay like:
http://code.google.com/apis/maps/documentation/examples/geoxml-kml.html
with:
http://mapgadgets.googlepages.com/cta.kml
If your KML file is too complex, GGeoXml cannot convert it to a tile
layer overlay. It must use GPolys instead which are often slow &
inaccurate. The actual selection criteria is undocumented.
The tool:
www.polyarc.us/gx
will show you the results of parsing your KML file. The property:
kmlOverlay.layer_id
contains the "root" of the tile layer overlay URL.
You will have to experiment a bit. One suggestion might be to split
your KML file into different pieces, one with just your polys & one
with everything else requiring "click" recognition. Perhaps you can
force GGeoXml to build a tile layer overlay for the first piece with
other stuff rendered in the API. Without knowing the actual tile
layer overlay threshold, trial & error will be required.
It looks like your KML file produces infowindows. Try eliminating
your infowindow description strings to see whether a tile layer
overlay results. If it does, perhaps you could define your markers &
infowindow contents in another KML file. Let "mapslt" / "mapsdt" to
the heavy lifting. Let the API provide the frivolous decorations.
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