将自定义标记（方形）添加到Gmap

Basically I want to draw a filled square and add it (and use it) as a marker to Gmap. I tried drawing a square and use it as a bitmap but it asks me for the x y coordinates and I don't know what values to put for that because the marker already uses lat/long. I am trying this but the position of the square is not right.I want to square to appear on the specified lat/long. Basically I want to draw a filled square and ad