14 ms·

Rebuilding Strava's Global Heatmap

32 points by mlerner 9y ago

ThatAndresV 9y ago
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?
- drewrobb 9y ago
  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.
s0rce 9y ago
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/hot/all 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/hot/ride https://labs.strava.com/heatmap/#12.41/-122.97170/37.71310/h...
- mrdmnd 9y ago
  AQUABIKE! This is neat =)
  - s0rce 9y ago
    Ooh, another interesting spot https://labs.strava.com/heatmap/#11.86/-118.45498/42.54408/hot/ride https://labs.strava.com/heatmap/#11.86/-118.45498/42.54408/h... Alvord lake/desert in Eastern OR
berttemme 9y ago
It seems they have removed tiling level 16 and 17 :-( For example: Level 16 on the old heatmap: http://globalheat.strava.com/tiles/cycling/color3/16/33705/21620.png 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/16/33705/21620.png https://heatmap-external-b.strava.com/tiles/ride/blue/16/337...
- drewrobb 9y ago
  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/16/33705/21620.png?px=256 https://heatmap-external-b.strava.com/tiles/ride/blue/16/337...
  - berttemme 9y ago
    ah good to know, is there a trick for level 17 also? For example https://heatmap-external-b.strava.com/tiles/ride/hot/17/67453/43168.png?px=256 https://heatmap-external-b.strava.com/tiles/ride/hot/17/6745... returns empty tile
    - drewrobb 9y ago
      level 16 is as far as it goes.
dracoola13 9y ago
Are you planning to update heatmap on iD editor for OSM? https://strava.github.io/iD/ https://strava.github.io/iD/
- drewrobb 9y ago
  Update done!
NelsonMinar 9y ago
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.
vinnieman232 9y ago
This is lovely. One question - did you consider a vector style versus a raster style? If so, why did you choose raster?
- drewrobb 9y ago
  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.

32 points by mlerner 9y ago

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?

drewrobb 9y ago
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.

s0rce 9y ago

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/hot/all 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/hot/ride https://labs.strava.com/heatmap/#12.41/-122.97170/37.71310/h...

mrdmnd 9y ago
AQUABIKE! This is neat =)
- s0rce 9y ago
  Ooh, another interesting spot https://labs.strava.com/heatmap/#11.86/-118.45498/42.54408/hot/ride https://labs.strava.com/heatmap/#11.86/-118.45498/42.54408/h... Alvord lake/desert in Eastern OR

berttemme 9y ago

It seems they have removed tiling level 16 and 17 :-( For example: Level 16 on the old heatmap: http://globalheat.strava.com/tiles/cycling/color3/16/33705/21620.png 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/16/33705/21620.png https://heatmap-external-b.strava.com/tiles/ride/blue/16/337...

drewrobb 9y ago
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/16/33705/21620.png?px=256 https://heatmap-external-b.strava.com/tiles/ride/blue/16/337...
- berttemme 9y ago
  ah good to know, is there a trick for level 17 also? For example https://heatmap-external-b.strava.com/tiles/ride/hot/17/67453/43168.png?px=256 https://heatmap-external-b.strava.com/tiles/ride/hot/17/6745... returns empty tile
  - drewrobb 9y ago
    level 16 is as far as it goes.

dracoola13 9y ago

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

drewrobb 9y ago
Update done!

NelsonMinar 9y ago

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.

vinnieman232 9y ago

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

drewrobb 9y ago
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.