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  • 计算山体阴影

    #!/usr/bin/env python
    # -*- coding: utf-8 -*-
    from osgeo import gdal
    from numpy import gradient
    from numpy import pi
    from numpy import arctan
    from numpy import arctan2
    from numpy import sin
    from numpy import cos
    from numpy import sqrt
    import matplotlib.pyplot as plt
    import subprocess
    
    
    def hillshade(array, azimuth, angle_altitude):
        """
        :param array: input USGS ASCII DEM / CDED .dem
        :param azimuth: sun position
        :param angle_altitude: sun angle
        :return: numpy array
        """
        #计算梯度
         x, y = gradient(array)
        #计算坡度
         slope = pi/2. - arctan(sqrt(x*x + y*y))
        #计算坡向
         aspect = arctan2(-x, y)
        #计算方位角
         azimuthrad = azimuth * pi / 180.
        altituderad = angle_altitude * pi / 180.
    
    
        shaded = sin(altituderad) * sin(slope)
         + cos(altituderad) * cos(slope)
         * cos(azimuthrad - aspect)
        # return 255*(shaded + 1)/2
        return aspect
    
    ds = gdal.Open('../geodata/092j02_0200_demw.dem')
    arr = ds.ReadAsArray()
    
    hs_array = hillshade(arr, 90, 45)
    plt.imshow(hs_array,cmap='Greys')
    plt.savefig('../geodata/hillshade_whistler.png')
    plt.show()
    
    # gdal command line tool called gdaldem
    # link  http://www.gdal.org/gdaldem.html
    # usage:
    # gdaldem hillshade input_dem output_hillshade
    # [-z ZFactor (default=1)] [-s scale* (default=1)]"
    # [-az Azimuth (default=315)] [-alt Altitude (default=45)]
    # [-alg ZevenbergenThorne] [-combined]
    # [-compute_edges] [-b Band (default=1)] [-of format] [-co "NAME=VALUE"]* [-q]
    
    create_hillshade = '''gdaldem hillshade -az 315 -alt 45 ../geodata/092j02_0200_demw.dem ../geodata/hillshade.tif'''
    
    #通过标准库中的subprocess包来fork一个子进程,并运行一个外部的程序
    subprocess.call(create_hillshade)
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  • 原文地址:https://www.cnblogs.com/gispathfinder/p/5790130.html
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