I want to be able to specify the radius of points effectively in meters. The API is configured so that the radius property is held to be constant for pixels, so that zooming in causes the heatmap to erode (I know you can make the heatmap not erode with the dissipating property, but this raises other issues, i.e., having to manually mess with the radius to get my heatmap to display properly. Here is the heatmaps reference.
Specifically, I'm trying to display a probability distribution on a map. I have the distribution in image form, and want to map the 0-1 weights to a heatmap layer. (I can, and don't want to, overlay the images).
Any suggestions?
Ok, I tried some things:
Using the Mercator Projection example (check the source) to extract the x,y pixel coordinates of any point from a latLng, to later use the geometry library, specifically the computeOffset function get another latLng a distance "DM" (in meters) to the right of the previous one, get the difference (in pixels) as an absolute value "DP" and from there you get your "pixelsPerMeter" ratio DP/DM.
So then, if you want your radius to be 100 meters you just set the properties to {radius:Math.floor(desiredRadiusPerPointInMeters*pixelsPerMeter)}
And to handle the change in zoom just use a listener
google.maps.event.addListener(map, 'zoom_changed', function () {
heatmap.setOptions({radius:getNewRadius()});
});
I uploaded a small example (try zooming), you can check if the distance looks right with the button on the bottom.