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I'm a little confused as to why Grab would hire a firm to update OSM via satellite images. OSM had to be more accurate than the outdated sat. images so why was

I'm a little confused as to why Grab would hire a firm to update OSM via satellite images. OSM had to be more accurate than the outdated sat. images so why was there a need in the first place?

rmc 8y ago
In many places, OSM can be improved with satellite imagery
- Kadin 8y ago
  Yes, agreed. In built-up areas it's not like roads move very often. I wonder if someone couldn't do "deltas" of satellite imagery to produce some sort of heatmap of how quickly various areas are changing. That would give you an idea of what areas are 'safe' to map based on satellite imagery, and what areas are changing too quickly and need to be mapped some other way. It would also give you a way of automatically flagging stale data on the vector map; if something hasn't been updated in 12 months and you know from imagery that the area is under heavy development, those map features are probably not trustworthy anymore.
  - perennate 8y ago
    Development Seed has a project Urchn that was trying to do something like that: https://medium.com/devseed/make-sense-of-urban-change-fabb9ff229d7 https://medium.com/devseed/make-sense-of-urban-change-fabb9f... The idea was to take satellite imagery of the same location from different timestamps and I believe use deep learning to determine if anything in the imagery changed. I don't think they've released any code for that project yet though. But for determining whether or not the imagery could be used in a certain region, it might make more sense to just compare the timestamps of the vector data and the imagery. For instance, if the road doesn't appear in the imagery, but the vector data timestamp is after the imagery timestamp, then keep the road. And don't add a road if it was covered by a map segment that was deleted some time between the imagery timestamp and the current time.
maxerickson 8y ago
Plenty of volunteer mapping is based on satellite data. People justifiably get irritated when they actually do a physical survey and then it gets overwritten remotely. As far as the imagery, DigitalGlobe provides relatively up to date imagery for most of the planet. The errors are probably more from overinterpreting the satellite data than from it being obsolete.
kozikow 8y ago
Not defending grab, but osm has lots of false negatives. Satellite image does not have to be outdated - you can get less than 6 months old satellite image accurate enough to extract roads and buildings from Digital Globe or Airbus. Shameless plug: At tensorflight.com we have deep learning models that can do just that.
- Krasnol 8y ago
  I guess it depends on the sat image source which leads to costs. I'm sure you can use the newest/best data for your company because you can pass on the costs to your clients.
  - kozikow 8y ago
    We indeed pass the cost of imagery to customers, but it's flexible. I.e. given the location and customer requirements we have a decision tree that picks the best image source from multiple providers based on freshness, spatial resolution, cost, and some other factors.
    - solarkraft 8y ago
      How does that tree approximately look? Which providers are there?
      - kozikow 8y ago
        > Which providers are there? In the "high spatial resolution" - i.e. 50 cm per pixel or less the well-known providers everyone is using are Digital Globe, Airbus or Nearmap. Above 50 cm it starts to get hard to confidently see enough detail. Google maps terms of service actually prohibits using satellite imagery for feature extraction ( https://cloud.google.com/maps-platform/terms/ https://cloud.google.com/maps-platform/terms/ ). Bing is the best on the cheap end. Actually, Bing donated imagery for OSM mapping purposes ( https://wiki.openstreetmap.org/wiki/Bing_Maps#Bing_Aerial_Imagery https://wiki.openstreetmap.org/wiki/Bing_Maps#Bing_Aerial_Im... ).
- 8y ago
moltar 8y ago
Aren’t you able to purchase fresh sat images on request? I’m pretty sure I’ve seen these services online.
- elil17 8y ago
  Fresh sat images are much more expensive than old ones
  - matte_black 8y ago
    How much?
sabas_ge 8y ago
I think that they wouldn't use only satellite imagery, but gps data from the fleet and user reports. See also https://qz.com/1481849/grab-southeast-asias-biggest-ride-hailing-firm-is-on-a-mapping-spree/ https://qz.com/1481849/grab-southeast-asias-biggest-ride-hai...
- Kadin 8y ago
  When OSM got started, the idea was to use GPS track data almost exclusively, or at least for the finer resolution stuff. The satellite imagery available freely at the time wasn't that good anyway. But cleaning a bunch of GPS tracks can be a real mess. Many GPS tracks don't include the error/accuracy measurements and just pretend to be infinitely-small points scattered in the general vicinity of what might be a road. I think people tend to overestimate how accurate their satnav or phone's GPS is, because in most uses it's "locked" to a road or other map feature. Anyway, not an intractable problem by any means, but preprocessing and cleaning GPS data to derive the actual terrain can be quite difficult. Paying somebody to click repeatedly on a satellite image might be temptingly easier.
  - Piskvorrr 8y ago
    That was by necessity, IIRC: almost everything else would be under restrictive licenses. The open data landscape has changed a lot since.

I'm a little confused as to why Grab would hire a firm to update OSM via satellite images. OSM had to be more accurate than the outdated sat. images so why was there a need in the first place?

rmc 8y ago

In many places, OSM can be improved with satellite imagery

Kadin 8y ago
Yes, agreed. In built-up areas it's not like roads move very often. I wonder if someone couldn't do "deltas" of satellite imagery to produce some sort of heatmap of how quickly various areas are changing. That would give you an idea of what areas are 'safe' to map based on satellite imagery, and what areas are changing too quickly and need to be mapped some other way. It would also give you a way of automatically flagging stale data on the vector map; if something hasn't been updated in 12 months and you know from imagery that the area is under heavy development, those map features are probably not trustworthy anymore.
- perennate 8y ago
  Development Seed has a project Urchn that was trying to do something like that: https://medium.com/devseed/make-sense-of-urban-change-fabb9ff229d7 https://medium.com/devseed/make-sense-of-urban-change-fabb9f... The idea was to take satellite imagery of the same location from different timestamps and I believe use deep learning to determine if anything in the imagery changed. I don't think they've released any code for that project yet though. But for determining whether or not the imagery could be used in a certain region, it might make more sense to just compare the timestamps of the vector data and the imagery. For instance, if the road doesn't appear in the imagery, but the vector data timestamp is after the imagery timestamp, then keep the road. And don't add a road if it was covered by a map segment that was deleted some time between the imagery timestamp and the current time.

maxerickson 8y ago

Plenty of volunteer mapping is based on satellite data. People justifiably get irritated when they actually do a physical survey and then it gets overwritten remotely. As far as the imagery, DigitalGlobe provides relatively up to date imagery for most of the planet. The errors are probably more from overinterpreting the satellite data than from it being obsolete.

kozikow 8y ago

Not defending grab, but osm has lots of false negatives. Satellite image does not have to be outdated - you can get less than 6 months old satellite image accurate enough to extract roads and buildings from Digital Globe or Airbus. Shameless plug: At tensorflight.com we have deep learning models that can do just that.

Krasnol 8y ago
I guess it depends on the sat image source which leads to costs. I'm sure you can use the newest/best data for your company because you can pass on the costs to your clients.
- kozikow 8y ago
  We indeed pass the cost of imagery to customers, but it's flexible. I.e. given the location and customer requirements we have a decision tree that picks the best image source from multiple providers based on freshness, spatial resolution, cost, and some other factors.
  - solarkraft 8y ago
    How does that tree approximately look? Which providers are there?
    - kozikow 8y ago
      > Which providers are there? In the "high spatial resolution" - i.e. 50 cm per pixel or less the well-known providers everyone is using are Digital Globe, Airbus or Nearmap. Above 50 cm it starts to get hard to confidently see enough detail. Google maps terms of service actually prohibits using satellite imagery for feature extraction ( https://cloud.google.com/maps-platform/terms/ https://cloud.google.com/maps-platform/terms/ ). Bing is the best on the cheap end. Actually, Bing donated imagery for OSM mapping purposes ( https://wiki.openstreetmap.org/wiki/Bing_Maps#Bing_Aerial_Imagery https://wiki.openstreetmap.org/wiki/Bing_Maps#Bing_Aerial_Im... ).
8y ago

moltar 8y ago

Aren’t you able to purchase fresh sat images on request? I’m pretty sure I’ve seen these services online.

elil17 8y ago
Fresh sat images are much more expensive than old ones
- matte_black 8y ago
  How much?

sabas_ge 8y ago

I think that they wouldn't use only satellite imagery, but gps data from the fleet and user reports. See also https://qz.com/1481849/grab-southeast-asias-biggest-ride-hailing-firm-is-on-a-mapping-spree/ https://qz.com/1481849/grab-southeast-asias-biggest-ride-hai...

Kadin 8y ago
When OSM got started, the idea was to use GPS track data almost exclusively, or at least for the finer resolution stuff. The satellite imagery available freely at the time wasn't that good anyway. But cleaning a bunch of GPS tracks can be a real mess. Many GPS tracks don't include the error/accuracy measurements and just pretend to be infinitely-small points scattered in the general vicinity of what might be a road. I think people tend to overestimate how accurate their satnav or phone's GPS is, because in most uses it's "locked" to a road or other map feature. Anyway, not an intractable problem by any means, but preprocessing and cleaning GPS data to derive the actual terrain can be quite difficult. Paying somebody to click repeatedly on a satellite image might be temptingly easier.
- Piskvorrr 8y ago
  That was by necessity, IIRC: almost everything else would be under restrictive licenses. The open data landscape has changed a lot since.