Rebuilding Strava's Global Heatmap | Hacker News Reader

Rebuilding Strava's Global Heatmap

medium.com

32 pointsmlerner14 comments

This is beautiful. Thanks so much for creating it. I’m hoping you can explain what looks like an anomaly though. Looking at Macritchie Reservoir in Singapore, there’s the expected hot outline on parts of its shore, but also a dead-straight oblong running roughly east-West for over 1km. Thing is, it can’t be a running track as it’s in the middle of the reservoir itself. Any thoughts on how this artefact got there?

I think that is some kind of rowing/swimming/boating course. It shows up in the running layer because a few people mislabel their activity types. It shows up much stronger in the water layer. Next update to the heatmap I intend to add a activity type classifier to help with these errors.

Absolutely lovely. The pedant in me wants to point out this isn't exactly a heatmap; there's no heat spreading blobbiness. It's more of a spatial histogram. Nothing wrong with that! The localized normalization of values using a CDF is very clever.

Cool article. I found some neat things in their data.

You can see the burning man "city" moves slightly each year creating an "echo" in the data.

https://labs.strava.com/heatmap/#13.49/-119.20399/40.78672/h...

Also, some people appear to have biked to the Farallone's https://labs.strava.com/heatmap/#12.41/-122.97170/37.71310/h...

AQUABIKE!

This is neat =)

Ooh, another interesting spot

https://labs.strava.com/heatmap/#11.86/-118.45498/42.54408/h...

Alvord lake/desert in Eastern OR

It seems they have removed tiling level 16 and 17 :-(

For example:

Level 16 on the old heatmap: http://globalheat.strava.com/tiles/cycling/color3/16/33705/2... Level 16 on the new heatmap (empty tile): https://heatmap-external-b.strava.com/tiles/ride/blue/16/337...

It is serving 512px tiles by default, which only go one level lower. At 256px, the level 16 requests are valid: https://heatmap-external-b.strava.com/tiles/ride/blue/16/337...

ah good to know, is there a trick for level 17 also? For example https://heatmap-external-b.strava.com/tiles/ride/hot/17/6745... returns empty tile

level 16 is as far as it goes.

Are you planning to update heatmap on iD editor for OSM? https://strava.github.io/iD/

Update done!

This is lovely. One question - did you consider a vector style versus a raster style? If so, why did you choose raster?

I think there are two parts:

1) Internal representation for building/serving: For vector, the data would have to be aggregated in some way otherwise it would be way too slow (for example, tiles having 10 million or more lines). How exactly to do that vector aggregation is a real challenge. If there is a good solution I'm not aware of it.

2) End product quality: everything is ultimately rasterized on the viewer's monitor. So if upstream resolution is high enough vector doesn't have any advantage here.

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