Elefix is a library to set elevation data to a list of latitude-longitude pairs. It also contains the scripts used to tune and evaluate the smoothing algorithm parameters.

Elefix library

In order to use this library you only need the following function:

set_altitudes(lats: List[float], lons: List[float], smooth: bool=True, window: int=151, polynom: int=2) -> List[float]

• lats and lons are the latitudes and longitudes.
• If smooth is False the altitudes will be the originals retrieved from the SRTM digital elevation model. If True the SRTM altitudes are smoothed with Savitzky-Golay filter.
• window and polynom are the filter's parameters. The defaults are optimized for mountain biking tracks.
• Returns a list of altitudes.

Tuning the smoothing parameters

I described the experiment I used to tune the parameters in this article (in process).

The scripts to train and test the parameters are included in evaluation/. I optimized the parameters for mountain biking activities. You can optimize them for other type of activities with the scripts provided.

SRTM data

This library needs the SRTM database in binary format. In the directory bin/ You will find the utility script srtm_asc_to_bin.py which helps you convert the ASCII database to the required format.

You can download the SRTM data from here: http://srtm.csi.cgiar.org/srtmdata

More details

In this article I explain all the details of the project, from the motivation to the results and accuracy of the resulting altitude data.

(in process)

Contact

Zuhaitz Beloki <[email protected]>