digital-elevation-model

Python for Processing Digital Elevation Models

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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
• Functions
• DEM Data
  • ASTERGDEM
  • EUDEM
• Dependencies
• Pipeline of Processing ASTERGDEM
• Usage
  • Usage of ASTERGDEM
  • Usage of EUDEM
• Results
  • DEM Images of London
  • Elevation of London
• References

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

• Update To access and download ASTERGDEM data set, see link.

• ~~ASTERGDEMv2.0 download link: https://earthexplorer.usgs.gov/~~

• See Introduction of ASTGDEMv20.pdf for detailed introduction and user guide (recommended).

EUDEM

• EUDEMv1.1 download link: https://land.copernicus.eu/imagery-in-situ/eu-dem/eu-dem-v1.1

• See here for detailed introduction and user guide.

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

2. 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.

3. Check the required version of GDAL Python Libraries in Terminal.

$ gdal-config --version

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

5. 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

6. 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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