More precise elevation data for GraphHopper routing engine

Summary

GraphHopper is used for many use cases and various companies around the globe have integrated it to provide outdoor trip planning for their customers. They all rely on precise elevation data: be it for displaying purposes, statistics regarding the incline, for bike routing to avoid hills or to better estimate energy usage of electric vehicles. Up until now we used the 90m precise elevation data of CGIAR a derivative of the NASA project (SRTM) and it served us well, but from time to time customers demanded more precise elevation data. Especially near mountains and along rivers the elevation errors were sometimes too high, because of a too low resolution which could sometimes even cause detours around those (non-existent) obstacles. Less precise elevation data means each cell with a single elevation value is relatively large (e.g. 90m x 90m instead of 30m x 30m). When a cell from a steep mountain incline overlaps part of a road, the road its elevation can suddenly spike to match the mountain, although the road itself doesn’t climb. Obtaining better and open elevation data with a global coverage is still a challenge, because there are many sources that publish them and it can get tricky to combine them and get elevation data usable for commercial usage. Over the last years there were a few approaches, but none of them satisfied our needs due to a lack of global coverage or they were too restrictive for commercial usage. With the mapterhorn project we decided to give this another try as this is the first project that has global coverage in mind as well as commercial usage. Over the last weeks we successfully integrated this data into our routing engine. (Scroll down for some examples.) This was a challenging undertaking because we had to handle a lot more data, which would have caused a massive slow down of the OpenStreetMap import pipeline if processed in a similar fashion. One part of the solution was to optimize the OpenStreetMap import pipeline and another part was ...