how do I get the bounds of a static google map?

Question

I am trying to plot geo coordinates (lat/lon) on an image I retrieve via Googles static Map API. I want to do this offline directly on the image via Ruby because I want to plot about 20,000 coordinates.

However, for this task, I need to specify the corner (top left & bottom right) coordinates. here is the link to my map: http://maps.google.com/staticmap?center=51.0,10.0&zoom=6&size=640x640&format=png&sensor=false

How can I get coordinates for the top left and bottom right corners of this map?

Thanks in advance :)

PS: My code for Lat/Lon -> X/Y is this for now:

def get_img_coords(lat, lon, w, h, lat_ul, lon_ul, lat_lr, lon_lr)
  { :x => (lon + lon_ul) * (w / (lon_lr-lon_ul)),
    :y => (lat + lat_ul) * (h / (lat_lr-lat_ul)) }
end

... assuming mercator projection of course.

map link problem: "This web site needs a different Google Maps API key." — jpwco
Have been looking at this one for a bit, tried a few things with public code that didn't work. I think the secret lies in taking the tile resolution at a given zoom level, moving from the known centre a known pixel distance to the edge, then computing the reverse EPSG:4326 projection to find the corner coordinates. — captainpete

JeremyKun JeremyKun · Accepted Answer · 2011-07-31T00:57:05

I ran into this problem before. Last time I checked (which was a bit over a year ago), the Maps API encoded most of its information via Geohashing. I suggest you start by looking at the Wikipedia page for it, and see this other stackoverflow question, which appears to have a Java implementation of what you want.

how do I get the bounds of a static google map?

2 Answers