4 ms·

I wonder if you could make a completely offline location service by correlating the results of a local 3d scan of the ground to the global model? Cruise missil

I wonder if you could make a completely offline location service by correlating the results of a local 3d scan of the ground to the global model? Cruise missiles already do something similar. How big is a mm scale model of the globe? It would almost completely negate the need for easily jammed and expensive to maintain gps satellites.

amanda99 3y ago
Apparently the US Navy has this kind of system for positioning of submarines to correct inertial navigation system errors. Allegedly they also have very good maps of large swaths of the ocean floor to make it useful.
- lupusreal 3y ago
  Very accurately measuring gravitational anomalies is important for this too.
  - 082349872349872 3y ago
    Plate tectonics would've been accepted much earlier if the seafloor magnetism maps hadn't been classified.
tlonny 3y ago
I imagine the earth isn't particularly static on the mm level.
- leoedin 3y ago
  True - buildings and exposed rock probably stay still, leaf litter and trees definitely don’t. You’d need to find enough of a stable reference to run your correlation - probably more useful in an urban area.
  - lupusreal 3y ago
    On a millimeter scale I expect weather/seasons will cause movement of the ground as the soil swells with water from rain, or water freezing.
  - darknavi 3y ago
    Taller buildings can flex up to a few feet in each direction actually!
- arethuza 3y ago
  I believe tectonic plates generally move about 15mm a year - which is pretty fast when you think about it!
  - 082349872349872 3y ago
    https://en.wikipedia.org/wiki/Plate_tectonics#Key_principles https://en.wikipedia.org/wiki/Plate_tectonics#Key_principles > Plate motions range from 10 to 40 mm/year at the Mid-Atlantic Ridge (about as fast as fingernails grow), to about 160 mm/year for the Nazca Plate (about as fast as hair grows)
shzhdbi09gv8ioi 3y ago
> I wonder if you could make a completely offline location service by correlating the results of a local 3d scan of the ground to the global model? It's possible, see https://news.ycombinator.com/item?id=39507267 https://news.ycombinator.com/item?id=39507267

amanda99 3y ago

Apparently the US Navy has this kind of system for positioning of submarines to correct inertial navigation system errors. Allegedly they also have very good maps of large swaths of the ocean floor to make it useful.

lupusreal 3y ago
Very accurately measuring gravitational anomalies is important for this too.
- 082349872349872 3y ago
  Plate tectonics would've been accepted much earlier if the seafloor magnetism maps hadn't been classified.

tlonny 3y ago

I imagine the earth isn't particularly static on the mm level.

leoedin 3y ago
True - buildings and exposed rock probably stay still, leaf litter and trees definitely don’t. You’d need to find enough of a stable reference to run your correlation - probably more useful in an urban area.
- lupusreal 3y ago
  On a millimeter scale I expect weather/seasons will cause movement of the ground as the soil swells with water from rain, or water freezing.
- darknavi 3y ago
  Taller buildings can flex up to a few feet in each direction actually!
arethuza 3y ago
I believe tectonic plates generally move about 15mm a year - which is pretty fast when you think about it!
- 082349872349872 3y ago
  https://en.wikipedia.org/wiki/Plate_tectonics#Key_principles https://en.wikipedia.org/wiki/Plate_tectonics#Key_principles > Plate motions range from 10 to 40 mm/year at the Mid-Atlantic Ridge (about as fast as fingernails grow), to about 160 mm/year for the Nazca Plate (about as fast as hair grows)

shzhdbi09gv8ioi 3y ago

> I wonder if you could make a completely offline location service by correlating the results of a local 3d scan of the ground to the global model? It's possible, see https://news.ycombinator.com/item?id=39507267 https://news.ycombinator.com/item?id=39507267