osmelevation

osmelevation annotates OpenStreetMap data with external elevation data from the NASA Digital Elevation Model (NASADEM).

correctosmelevation performs corrections on the elevation data in OpenStreetMap data.

Adding elevation data to OpenStreetMap

The tool osmelevation adds the tag ele=* to each node in OSM. This tag contains the elevation above sea level in meters of the node's location. If a node already has a ele=* tag, nothing gets changed.

Correcting elevation data in OpenStreetMap

The tool correctosmelevation performs corrections on elevation data along routes in OSM. This includes the following OSM objects:

• (1) Relations with tag type=route
• (2) Relations with tag waterway=river
• (3) Ways with tag highway=*

The following corrections are performed:

• Apply a smoothing algorithm to the elevation along routes found in (1) and (3)
• For tunnels/bridges found in (1), straighten the elevation of the tunnels/bridges
• Make sure that rivers do not flow uphill (2)

Getting started

Docker

Build and run the Docker image with

$ docker build -t osmelevation -f Dockerfile .
$ docker run -it -v <path to input data>/:/OsmElevation/extern/ --name osmelevation osmelevation

where "path to input data" contains a folder with NASADEM files and OSM files where the elevation data should be added to. In the docker image, this data will be accessible in extern/

Without Docker

On Ubuntu 20.04 the following libraries and packages are required to build osmelevation and correctosmelevation:

g++ libboost-all-dev libbz2-dev cmake make

• Libosmium
  • Expat
  • protozero
  • zlib
• libzip

Build osmelevation and correctosmelevation:

$ mkdir build && cd build && cmake .. && make -j4 && cd ..

Usage

For the first tool osmelevation, prepare a folder containing NASADEM files and an OSM input file. Elevation data can be added to an OSM input file by calling

$ ./build/osmelevation <NASADEM files directory> <OSM input file> <OSM output file>

For the second tool correctosmelevation, an with elevation data annotated OSM input file is needed. The elevation data in an OSM input file can be corrected by calling

$ ./build/correctosmelevation <OSM input file> <OSM output file>

Assess ./build/osmelevation and ./build/correctosmelevation for further options.

Important remark

For the second tool correctosmelevation, complete OSM relations with tag type=route and waterway=river must be present. Otherwise, no corrections will be performed on these (incomplete) relations. When creating geographic extracts with tools like osmium, options must be chosen to not clip relations with these tags at the borders of the extracts. To include complete relations with tag type=route, call osmium with -s smart -S types=route. To also include relations with tag waterway=river, osmium must be called with -s smart -S types=any as there is no option specifically for this tag.

Obtaining NASADEM files

NASADEM elevation data are derived from the original SRTM data. For more information, visit the official website. All available NASADEM files are downloadable from the LP DAAC Data Pool. A free Earthdata account is required. For bulk downloads, follow the official instructions provided by NASA. A txt file containing all NASADEM files urls is provided with nasadem_urls.txt.