I have the same issue and could not solve it yet.
A search based on the distance from the center is a good start but does not solve the problem, because we don’t know what radius is needed to cover the whole map. It depends on the current zoom level of the map, and I was not able to retrieve it. It is possible to set the zoom level, but I cannot find how to access the current zoom level…
I think it would be quite simple to make this field accessible, and it would open many possibilities for us to play with maps… any chance we get an update on this?
The distance in km that the map covers also depends on the width / height of the google map object itself, in pixel. So we would need to know, for each zoom level, how many kilometers is one pixel (the scale of the map).
Well, it would be easier to directly know the bounding box (i,e. position of the top left and bottom right corners, or the top left corner + width and height in km)…
There is a lot of place for improvement here, I would really appreciate to have new options to better control and play with maps!