def elevation( self, lng, lat, interpolate=True ):
        if lng < self.left or lng >= self.right or self.bottom <= lat or lat > self.top:
            return None
        
        x = (lng-self.left)/self.cellsize
        y = (self.top-lat)/self.cellsize
        
        ulx = int(floor(x))
        uly = int(floor(y))
        
        ul = self.cell( ulx, uly )
        if not interpolate:
            return ul
        ur = self.cell( ulx+1, uly ) 
        ll = self.cell( ulx, uly+1 )
        lr = self.cell( ulx+1, uly+1 )
        
        cellleft = x%1
        celltop = y%1
        um = (ur-ul)*cellleft+ul #uppermiddle
        lm = (lr-ll)*cellleft+ll #lowermiddle
        
        return (lm-um)*celltop+um
dataset/ETHPy150Open bmander/graphserver/pygs/graphserver/ext/ned/elevation/elevation.py/GridFloat.elevation/swapped operands of `<=`