Thread: Why GPS without inertial navigation fails.

Actual teme for ppl who driving alote in city with high buildings

The real issue is "why inertial navigation fails without GPS"

Inertial system are far less accurate and hard to use than GPS:
- you need to know your coordinates when the system starts
- you need to keep position while it initialise (some minutes in aircraft systems)
- you need to refix due to gyro drift (that's why they use GPS to correct position errors)

The good in INS is that they are a lot faster in response than GPS but we don't really need this kind of systems in our car.
What Pioneer and some others uses is a compass to correct the heading information from GPS when you're not moving or moving very slowly (an inertial system is far more complex!). When you loose GPS signal the navigator uses your last known speed and current heading to assume your current position.
This is absolutely feasable with our carputers: it's matter of finding a compass (similar to http://www.robot-electronics.co.uk/s...CMPS032004.htm) and write a small application to correct GPS messages.
Cheers

I never have an issue with being off the road.

Hardware - the Ebay GPS mouse (WAAS enabled)
Software - iGuidance v.20

So even if i did buy one of these "commercial Gyro/GPS systems" could i use the current software (iGuidance2)? or would i have to use a special software that accepted the other data? I would assume that the software would have to support differential positioning before you could utilize it

Originally Posted by Laidback

And some software has the 'snap to road' feature, which keeps you on the road as well. I find mine pretty accurate!

except when it decides you took the turning off the motorway junction when you didn't (or vice versa)

The conspiracy theories of non accurate GPS co-ordinates rear their head yet again!!

I only find that I'm off the map when I take the bypass that hasn't been added yet. Always meet the road again soon though.

in norcal locations are always perfectly matching onto the maps on my computer. exceptions are recently added/removed exits, etc. technically the position could be a few feet off but hey I need driving directions not instructions to locate a pin. cost/benefit is not worth for me to buy a nav w/ gyro. ymmv.
--ccb

As said before, the real problems start when you loose your gps signals. There are a lot of occasions: tunnels, woods and certainly cities with a lot of high buildings (where navigation could certainly prove it's point!).

Also, when I had my VDO system, I liked the fact that I could see the direction I was headed to on the map, even when standing still.

@antimatter: I think these systems simulate a very accurate GPS by sending modified/recalculated NMEA data to the serial port, so your existing software would still work, even with bad/no gps reception.

@Antimatter, the device I've been using to test our I2C code for Seth's radio project is the CMPS03 compass (mentioned a few posts back). You can get it for around $50. I plan to do exactly what JC-S60 just said and integrate this data with my GPS data stream and then output a new NMEA stream. The software doesn't need to know about it.

I already have my GPS reader code and have built a small circuit to sample my speed sensor over the serial port (note: this can probably be done a bit more accurately with a small MCU). I still need to do some in-car testing on both devices to better understand their limitations. After that I'll do the integration and then I'll try it out with Mappoing and Street Atlass -- but it should work with anything.