General > General Technical Chat

Global Positioning System navigating in three dimensions

(1/3) > >>

jonovid:
can the GPS navigate in three dimensions?
can GPS signals be used to acquire the height above sea level?
with in 4 to 5 Meters?
if not why not?
to know the road gradients in a city for cycling. or walking trail
is this or that street flat or has a gradient?

Brumby:
GPS only does positioning in 3 dimensions.  Mapping 3D coordinates to the irregular shape of the Earth's surface was one of the challenges when being implemented for us ground dwellers.

As for accuracy, I would expect elevation would have similar precision to lateral position.  It all depends on how good a set of signals you are able to receive.

Navigation in 3 dimensions, however, would only be possible if the maps used contained altitude information and the application was programmed to process this information ... which is something I don't know.

However, I think it would be interesting if the turn-by-turn instructions said "Turn right in 100 metres then ascend 15 metres".

BravoV:
Not sure about accuracy, remembered last time when I was on a plane, while sitting near window seat, run the GPS app at my phone, it showed clearly the altitude, speed and coordinate.

kjpye:
GPS certainly handles elevation -- I use it all the time, but it's accuracy is significantly worse than horizontal accuracy.

Most, if not all, of the visible satellites are near the horizon. Consequently the distance to those satellites varies relatively slowly with your elevation, and so the error bars on vertical measurements are much larger than those for horizontal measurements.

Berni:
GPS can only work in 3D because the earth is round (At least according to sane people)

But due to the earth not being a perfect sphere the GPS module has to use a globe approximation to figure out where sea level actually is, so depending on what geode model is used the altitude result might be slightly different from the real altitude. But given that you want to record altitude variation of a cycling path that is nothing to worry about since a cycling path is not going to be long enough for this to become a big problem.

If you want some redundancy to GPS signal loss you can also add a barometric altitude sensor. They can vary a bit due to weather air pressure changes, but you can compensate that out by calibrating it to the GPS altitude.

EDIT:
Oh and GPS modules are also programed to stop working on purpose when above a certain very very high altitude or breaking the speed of sound. This is due to a silly US law to prevent them from being used as guidance for intercontinental ballistic missiles. I'm pretty sure if the opposing army has the budget for such a missile they also have the budget to figure out how to circumvent this safety feature.

Navigation

[0] Message Index

[#] Next page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod