“ sa hcus ,ereht tuo melborp siht ot snoitulos laitnetop rehto era ereht ,sey dnAhttp://stackoverflow.com/questions/3645649/i-need-to-know-the-predefined-point-is-in-the-sea-or-on-the-land , but they suffer from significant disadvantages: the first linked answer requires an additional web service call; the second would be awkward to make work at sufficiently high resolution for any measurements in coastal areas at higher map zoom levels. ”