skifile.py 文件源码

def angularpixelarea(self):
        # get the first instrument element
        instruments = self.tree.xpath("//instruments/*[1]")
        if len(instruments) != 1: raise ValueError("No instruments in ski file")
        instrument = instruments[0]
        # get the distance in m
        d = self.units().convert(instrument.get("distance"), to_unit='m', quantity='distance')
        # get the field of view in m
        fovx = self.units().convert(instrument.get("fieldOfViewX"), to_unit='m', quantity='length')
        fovy = self.units().convert(instrument.get("fieldOfViewY"), to_unit='m', quantity='length')
        # get the number of pixels
        nx = int(instrument.get("pixelsX"))
        ny = int(instrument.get("pixelsY"))
        # calculate the angular pixel area
        sx = 2 * arctan(fovx / nx / d / 2)
        sy = 2 * arctan(fovy / ny / d / 2)
        return sx * sy

    ## This function returns a list of instrument names, in order of occurrence in the ski file.