5 ms·

Micro-mapping manholes and benches seems like something that would really benefit from the precision of RTK/PPP GPS. The built-in GPS provider in my phone is ab

Micro-mapping manholes and benches seems like something that would really benefit from the precision of RTK/PPP GPS. The built-in GPS provider in my phone is absolutely not up to the task. Suppose I have a bunch of hardware sitting around, a base/CORS reference, etc. Is there an accepted best-practice way to pipe it into my phone to let this app use it? Or to take logs in my backpack and post-align the data when I get home?

AlphaWeaver 4y ago
On Android, in Developer Settings, it's possible to register an app as a Mock Location provider. I'm not sure the interface your app needs to surface to show up in that list for selection, but in theory that API existing means there's a potential path for this. Your app could interface with more accurate external sensors, and then set the phone's GPS fix to be what the sensors read. Assuming that the issue is lack of accuracy at the sensor level and not lack of precision at the software / API level.
- uneekname 4y ago
  This is the way. I had a lot of success using Mock Location for a mapping project this spring. I'm pretty sure mapping applications have to explicitly allow it, though. For some reason Google Maps refused to acknowledge my mock location IIRC. But I've never had issues with OSM mapping apps.
michaelt 4y ago
If the hardware you've got sitting around is a proper high-precision GPS system like a Trimble R2 or suchlike, the normal practice would be to use the data logging features built into it. But are you sure the GPS in your phone isn't good enough to map the location of benches? I've seen phones get within a meter or so, under good conditions - more than sufficient to get someone close enough to see a bench.
- myself248 4y ago
  Close enough to see a bench is one thing, but close enough for the bench to be located properly in relation to the manhole, is something else entirely. I'm sitting on a couple Ublox F9P's, one of which I need to get back in service as a Galmon monitor station but which also serves as my RTK base, and the other is on a quad that I'm not flying anymore so that's my rover.
  - ygra 4y ago
    Personally I try to align new POIs that I cannot see on aerial imagery as well as I can to existing geometry like building outlines or streets/paths. Either one of those may we wrong since aerial images often have an offset that varies depending on where you are and you can't really tell from the map which points are accurate and which ones aren't. So your bench that's accurate to 10 cm may just as well be moved by someone else again because it's "clearly near that path intersection and not 10 m away from it". Maps basically lie all the time and every map is an imperfect approximation of reality. Of course if your envisioned data consumers are blind people that are guided by surveying GPS equipment to that bench so they can just sit and be confident in actually sitting on the bench ... well, yeah, that might work. But I don't think that's a particular compelling use case and most people when they're looking for the bench that's on their map will find it just fine if it's not that accurate. Interesting tidbit: Hiking guideposts around here all have UTM coordinates written on them and a few of them are a bit wrong, at least compared with other geometry sources that should in theory also be accurate (like cadastre data).

AlphaWeaver 4y ago

On Android, in Developer Settings, it's possible to register an app as a Mock Location provider. I'm not sure the interface your app needs to surface to show up in that list for selection, but in theory that API existing means there's a potential path for this. Your app could interface with more accurate external sensors, and then set the phone's GPS fix to be what the sensors read. Assuming that the issue is lack of accuracy at the sensor level and not lack of precision at the software / API level.

uneekname 4y ago
This is the way. I had a lot of success using Mock Location for a mapping project this spring. I'm pretty sure mapping applications have to explicitly allow it, though. For some reason Google Maps refused to acknowledge my mock location IIRC. But I've never had issues with OSM mapping apps.

michaelt 4y ago

If the hardware you've got sitting around is a proper high-precision GPS system like a Trimble R2 or suchlike, the normal practice would be to use the data logging features built into it. But are you sure the GPS in your phone isn't good enough to map the location of benches? I've seen phones get within a meter or so, under good conditions - more than sufficient to get someone close enough to see a bench.

myself248 4y ago
Close enough to see a bench is one thing, but close enough for the bench to be located properly in relation to the manhole, is something else entirely. I'm sitting on a couple Ublox F9P's, one of which I need to get back in service as a Galmon monitor station but which also serves as my RTK base, and the other is on a quad that I'm not flying anymore so that's my rover.
- ygra 4y ago
  Personally I try to align new POIs that I cannot see on aerial imagery as well as I can to existing geometry like building outlines or streets/paths. Either one of those may we wrong since aerial images often have an offset that varies depending on where you are and you can't really tell from the map which points are accurate and which ones aren't. So your bench that's accurate to 10 cm may just as well be moved by someone else again because it's "clearly near that path intersection and not 10 m away from it". Maps basically lie all the time and every map is an imperfect approximation of reality. Of course if your envisioned data consumers are blind people that are guided by surveying GPS equipment to that bench so they can just sit and be confident in actually sitting on the bench ... well, yeah, that might work. But I don't think that's a particular compelling use case and most people when they're looking for the bench that's on their map will find it just fine if it's not that accurate. Interesting tidbit: Hiking guideposts around here all have UTM coordinates written on them and a few of them are a bit wrong, at least compared with other geometry sources that should in theory also be accurate (like cadastre data).