3 posts tagged with "valhalla"

From Morskie Oko, the lake under the highest peaks of the Polish Tatras, a trail climbs to Czarny Staw pod Rysami, the next lake up. It is 500 metres long and rises 180 metres. The time written for it is 30 minutes up and 20 minutes down. At Valhalla's default walking speed of 5.1 km/h, the distance alone takes six minutes.

Our routing runs on Valhalla, and its tiles already store the elevation along every edge. In June we tried to turn that elevation into hiking times that agree with the times people walk by. Here is what we compared against, the models we tried on the way, and the curve that went into the tiles.

One edge of a motorway in eastern Germany was driven at about 120 km/h until March 2024. For the next twenty months the GPS traces on it ran at 85 to 95 km/h, and since December 2025 they are back above 120. By 3 June, the last day of our June observations, the edge had 1,503 of them, and their plain median was 99.9 km/h:

Each dot is one traversal, day and night together, faded by how much it counts. Our traffic data gives every road a day speed and a night speed for Valhalla, and for this road the plain median is wrong by more than 20 km/h. This post is about how much an old observation should count, and about the decisions that have to be right before that question even makes sense.

In our GPS data, German urban motorways run at 84% of their weekly average speed between seven and eight on Monday morning, and at 113% at the same hour on Sunday. This is the week of that road group: the faint line is every five-minute slot, the solid one the average over an hour.

Hover over the week to read it. The Friday afternoon is slow too. Other groups have other weeks: suburban main roads in Ukraine lose speed for the whole working day.

Valhalla can take a curve like this for every edge of its graph and use it when a route has a departure time. In May we tried to give it one from our own GPS data. This post is about how much of such a curve the data could support.