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Python for Processing Digital Elevation Models

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English Version | 中文版

This is a Python implementation of transforming, projecting, converting, and visualizing Digital Elevation Models as well as reading their elevation of given locations.

Table of Contents

Terms and Abbreviations

Term Abbreviation Remark
Digital Elevation Model DEM -
Geographic Coordinate System GCS [Longitude, Latitude, Elevation] on 3D ellipsoid
Projected Coordinate System PCS [X-coor, Y-coor, Elevation] on 2D plane
Georeferenced Tagged Image File Format GeoTIFF Data Format of DEM (e.g., .tif)
European Petroleum Survey Group EPSG EPSG codes identify different GCSs and PCSs
1984 World Geodetic System WGS-84 GCS, EPSG-4326, approx. the ellipsoid of Earth
Pseudo Mercator (Web Mercator) - PCS of WGS-84, EPSG-3857
1936 Ordnance Survey Great Britain OSGB-36 GCS, EPSG-4277, approx. the ellipsoid of Britain
British National Grid BNG PCS of OSGB-36, EPSG-27700
1989 European Terrestrial Reference System ETRS-89 GCS, EPSG-4258, approx. the ellipsoid of Europe
Lambert Azimuthal Equal-Area LAEA PCS of ETRS-89, EPSG-3035

Functions

  • Transforming DEM from one GCS (e.g., WGS-84) to another GCS (e.g., OSGB-36).

  • Projecting DEM from one GCS (e.g., OSGB-36) to the related PCS (e.g., BNG).

  • Converting DEM from one PCS (e.g., LAEA) to the related GCS (e.g., ETRS-89).

  • Visualizing DEM in PCS as a 2D image.

  • Reading the elevation of given locations from DEM in GCS.

DEM Data

ASTERGDEM

EUDEM

Dependencies

  • gdal (osgeo) 1.11.3
  • matplotlib 3.0.2
  • numpy 1.15.4
  • pandas 0.23.4

The following procedures (1-2) for installing GDAL are recapitulated from mothergeo.

  1. Install GDAL Development Libraries and export environment variables for the compiler in Terminal.
$ sudo apt-get install libgdal-dev

$ export CPLUS_INCLUDE_PATH=/usr/include/gdal
$ export C_INCLUDE_PATH=/usr/include/gdal
  1. Install GDAL Python Libraries in Terminal.
$ pip install GDAL

If it comes with the error: cpl_vsi_error.h: No such file or directory, please try the following procedures.

  1. Check the required version of GDAL Python Libraries in Terminal.
$ gdal-config --version

  1. Download the source file (e.g., gdal-1.11.3.tar.gz) of the related GDAL version (e.g., 1.11.3) from here.

  2. Manually install GDAL Python Libraries in Terminal.

$ cd path/of/downloaded/gdal/package

~$ tar -xvzf gdal-{VERSION}.tar.gz
# E.g., ~$ tar -xvzf gdal-1.11.3.tar.gz

~$ cd extracted/gdal/folder
# E.g., ~$ cd gdal-1.11.3

~$ cd swig
~$ cd python
# The setup.py exists in this directory.

~$ python setup.py build_ext --include-dirs=/usr/include/gdal/
~$ python setup.py install
  1. Run >>> from osgeo import gdal in Python. If no error occurs, the installation is accomplished.

Pipeline of Processing ASTERGDEM

Usage

The directory of source DEMs is shown as below.


└── Data/
    ├── DATA_ASTGDEMv20/
    │   └── EPSG4326_s/
    │       ├── ASTGTM2_N51W001_dem.tif
    │       └── ASTGTM2_N51E000_dem.tif
    └── DATA_EUDEMv11/
        └── EUDEMv11_EPSG3035.tif

Usage of ASTERGDEM

  1. Download DEMs ASTGTM2_N51W001_dem.tif and ASTGTM2_N51E000_dem.tif from here.

  2. Copy DEMs to the folder DATA/DATA_ASTGDEMv20/EPSG4326_s/.

  3. To process ASTREGDEMv2.0 DEMs, run run_DEM_ASTGDEMv20.py or run_DEM_ASTGDEMv20_ipy.ipynb.

  4. The log of running run_DEM_ASTGDEMv20.py can be seen in Log_run_DEM_ASTGDEMv20.txt.

Usage of EUDEM

  1. Download DEM eu_dem_v11_E30N30.tif from here.

  2. Copy DEM to the folder DATA/DATA_EUDEMv11/ and rename it as EUDEMv11_EPSG3035.tif.

  3. To process EUDEMv1.1 DEM, run run_DEM_EUDEMv11.py or run_DEM_EUDEMv11_ipy.ipynb.

  4. The log of running run_DEM_EUDEMv11.py can be seen in Log_run_DEM_EUDEMv11.txt.

Results

DEM Images of London

  • The DEM Image of ASTERGDEMv2.0 in Pseudo Mercator PCS

  • The DEM Image of ASTERGDEMv2.0 in BNG PCS

  • The DEM Image of ASTERGDEMv2.0 in LAEA PCS

Elevation of London

  • The elevation of 24 locations in London (meter)
No. of Location 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
ASTGDEMv20_WD 18 18 38 40 65 26 35 31 17 79 13 41 62 82 9 13 31 31 15 22 24 40 8 40
ASTGDEMv20_UK 14 14 36 25 60 37 33 40 20 68 12 25 62 59 15 18 22 22 15 21 14 33 8 47
ASTGDEMv20_EU 18 18 38 40 65 26 35 31 17 79 13 41 62 82 9 13 31 31 15 22 24 40 8 40
EUDEMv11_WD 12 12 37 30 61 25 29 36 11 66 11 31 64 79 7 27 25 25 14 15 13 32 5 36
EUDEMv11_UK 12 12 37 26 58 30 32 35 11 71 8 30 66 78 8 26 24 24 8 16 13 32 9 35
EUDEMv11_EU 12 12 37 30 61 25 29 36 11 66 11 31 64 79 7 27 25 25 14 15 13 32 5 36

References

[1] EPSG 4326 vs EPSG 3857 (projections, datums, coordinate systems, and more!)

[2] Coordinate systems and projections for beginners

[3] CSDN Blog


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