Calculate elevation range

This notebook calculates the minimum and maximum elevation within a study area defined by a vecotor polygon boundary from a raster digital elevation model.

import statements



In [80]:

    
from geo.models import Raster
from geo.models import Boundary

import rasterio
from shapely.geometry import shape
import numpy
import numpy.ma
import rasterio.mask

from matplotlib import cm as colormaps
from matplotlib import pyplot
%matplotlib inline

load raster information from database



In [3]:

    
dem_record = Raster.objects.get(name='dem')

load study area boundary



In [45]:

    
boundary_record = Boundary.objects.get(name='study area')
boundary = [eval(boundary_record.geometry.geojson)]

mask raster with boundary



In [104]:

    
with rasterio.open(path=dem_record.filepath, mode='r') as source:
    dem, transform = rasterio.mask.mask(source, boundary, crop=True, nodata=-9999)
dem = numpy.ma.masked_equal(dem.data, -9999)

calculate the minimum and maximum value



In [106]:

    
dem.min()









    Out[106]:





560



In [107]:

    
dem.max()









    Out[107]:





1009

plot the masked raster



In [117]:

    
pyplot.imshow(dem[0], cmap='viridis', vmin=dem.min(), vmax=dem.max())
pyplot.tick_params(bottom=False, labelbottom=False,
                   left=False, labelleft=False,
                   top=False, right=False)
pyplot.axes().set_frame_on(False)
cb = pyplot.colorbar()