gistfile1.txt

    options=['COMPRESS=LZW',"BLOCKXSIZE=256", 'TILED=YES', 'COPY_SRC_OVERVIEWS=YES']
    driver = gdal.GetDriverByName('GTiff')
    outRaster = driver.Create(filename, cols, rows, 2, gdal.GDT_UInt16 , options=options)
    outRaster.SetGeoTransform((originX, pixelWidth, 0, originY, 0, pixelHeight))
    outband = outRaster.GetRasterBand(1)
    outband.WriteArray(array)

    zband = outRaster.GetRasterBand(2)
    zs = np.empty_like(array)
    zs.fill(z)
    zband.WriteArray(zs)

    outRaster.BuildOverviews( 'nearest', overviewlist = [1, 2, 4])

    zband.FlushCache()
    outband.FlushCache()
    outRaster.FlushCache()