Investigate how to use DEM to get elevation about trackeditor HOT 3 CLOSED

Using python some DEM info has been loaded, ilha das Flores and ilha do Corvo from Azores:

import tifffile as tiff
import matplotlib.pyplot as plt
import rasterio

tfile = tiff.imread('eu_dem_v11_E00N20.TIF')
tfile.shape
tiff.imshow(tfile)
plt.show()

Source: https://gis.stackexchange.com/questions/337343/altitude-extraction-from-a-dem-tiff-file-using-python

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A deeper analysis of this can drive to the creation of an API to get elevation from given coordinates.

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This small code allows to open 'one band' of the tiff file. However, when using a larger file a MemoryError is raised:

numpy.core._exceptions.MemoryError: Unable to allocate 5.96 GiB for an array with shape (1, 40000, 40000) and data type float32

import rasterio

# Which band are you interested. 
# 1 if there is only one band
band_of_interest = 1

# Row and Columns of the raster you want to know
# the value
row_of_interest = 30
column_of_interest = 50

# open the raster and close it automatically
# See https://stackoverflow.com/questions/1369526
with rasterio.open('eu_dem_v11/eu_dem_v11_E00N20.TIF') as dataset:
    band = dataset.read(band_of_interest)
    print(band)

value_of_interest = band[row_of_interest][column_of_interest]
print(value_of_interest)
print(len(band))

l_band = []
for b in band:
	l_band.append(len(b))
print(min(l_band), max(l_band))

Fortunately, there is some information on how the files are constructed:

Additional information
The EU-DEM is a 3D raster dataset with elevations captured at 1 arc second postings (2.78E-4 degrees) or about every 30 metre.
All three datasets are made available as tiles (5x5° or 1000x1000km) and as single files:

• EU-DEM in ETRS89 geographic (EPSG code 4258)
• EU-DEM in ETRS89-LAEA (EPSG code 3035)
• Colour shaded relief image over Europe in ETRS89-LAEA (EPSG code 3035)
  The datasets are encoded as GeoTIFF with LZW compression (tiles) or DEFLATE compression (European mosaics as single files).

https://www.eea.europa.eu/data-and-maps/data/eu-dem

Therefore, the firsts steps to create an API would be:

1. Read small tif file, such as eu_dem_v11_E10N20, and get altitude given coordinates.
2. Read tif files by reduced chunks.
3. Load data to a SQL database.

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