GPS altitude precision and medical application?

[gps11]

Guys... i just registered here because I thought you'd be the people to ask... It's not exactly about the TOMTOM...

It's more about the future of GPS tech innovation.... first of all.. .does anybody know
how accurate is GPS?
And when will we get millimeter accurate altitude?

 

[gps11]

PS...

This would be useful for tracking locations in multistory buildings and points in trees etc... i found this one article saying that rice size gps beacons are used in cancer surgery: http://journik.com/convergence/gps-...mal-side-effects-by-virginia-hospital-center/

So i'm wondering what else is on the horizon.

What rumors have you heard?

 

[dhn]

May I ask why you show your location not in the country you appear to be posting from?

 

[gps11]

I have a second home in Seoul Korea... on vacation right now. ummm... not sure how this question applies though?? =)

 

[dhn]

Just doing my job as a moderator, that's all..........

 

[gps11]

Ahhh... right... that canned mystery ham problem! =)

Well... I'm a real person... and very interested in GPS tech... so hopefully, I'll be a helpful community member! Thanks dhn!

 

[dhn]

Thanks for your understanding..... when a new poster provides a link to a site (especially an uncommon one to us), we just have to check it out......

Okay, I'm moving this thread to a forum where it may get more visibility...........

 

[Andy_P]

I don't think current GPS technology is very accurate for height.
Certainly the add-on programs that show height above sea level are only accurate to a few yards.

Actually, I'm amazed and rather sceptical at that report that they are using GPS for medical uses with millimetre accuracy at all!

THIS official government site suggests they are delivering horizontal accuracy of around 1-3m in the civilian system (only 7.8 meters at a 95% confidence) unless they use an additional "augmentation system".
Another .pdf on that site suggests

well designed GPS receivers have been achieving horizontal accuracy of 3 meters or better and vertical accuracy of 5 meters or better 95% of the time.

 

[canderson]

While the expression "GPS" is being used in a cute fashion, what's being described in that medical article isn't in any way related to the GPS system having to do with satellites. http://calypsomedical.com/

 

[gps11]

dhn, thanks for the move!
did you guys see the ted.com talk about gps??? it says that all our phones are capable of 2mm accuracy right now!

but that there's a law that needs to be passed for that to happen.

and that ted talks video talks about gps spoofing techniques... really interesting.

actually,,, fascinating

 

[Andy_P]

I'd take that "2mm" story with a very large pinch of salt!

 

[canderson]

If you are referencing the Humphreys seminar, you need to listen to that lecture again. No law is going to change the math (I suspect you refer without realizing it to the day when Clinton told the military to shut off the 'selective accuracy' feature of the existing system), and the current math doesn't allow your phone / GPS to provide anything close to 2mm accuracy.

First, the carrier phase technology that Humphreys talks about doesn't yet exist.

Second, he seems completely unaware of the fact that there are several OTHER non-receiver based reasons for calculated position inaccuracies (what those in the business call DOP, or "dilution of precision") that cannot be resolved by any GPS chip. It is for that reason that companies in the commercial GPS / survey business find it necessary to set up local reference points at known locations in order to get anything close to the accuracy that they are getting now.

Spoofing, on the other hand, is real enough. However, that can be detected due to anomalies in signal strength. Problem is, not enough companies making 'mission critical' gear are making use of that and other techniques to assure their gear isn't being spoofed.

 

[gps11]

WOW... you guys really know what you're talking about! Sheesh! Glad im here!

 

[canderson]

And sometimes we talk garbage. When I said "Selective Accuracy" above, it should have been "Selective Availability", which in essence was really 'selective availability to decent accuracy'.

Here's a pretty decent layman's level article on GPS accuracy that explains many of the other possible DOP sources that ruin the whole 2mm concept using satellites in the sky today:

http://www.radio-electronics.com/info/satellite/gps/accuracy-errors-precision.php

There are mechanisms to help deal with some of this error (for example, read up on why the FAA set up their WAAS system using a couple of existing satellites and how that helps a bit), but nothing close to the accuracy Humphreys talks about.

 

[toddzjeep]

Pardon my ignorance, but isn't the government (US) put a mandate into affect that GPS units were not to be accurate to 15 ft due to terrorists using them to navigate aircraft into buildings? Using coordinates?? Altitude readings?? LIke what happened to the twin towers, New York (9-11) ?????

 

[canderson]

No, no such mandate. WAY back when, there was something known as "selective availability" that threw all commercial/civilian units off to the tune of about 100 meters in one direction or another. Hasn't been true since they switched that off in May 2000. Now accuracy is a function of the current view of the sky and the quality of the GPS. 15' isn't impractical, believe me. I have units that will track to slightly less than that on a precision benchmark on a regular basis.

 

[drledger]

I missed this thread while away on vacation but I will add my thoughts anyway. GPS is, at least at this time, just "very close". As noted earlier, there are simply too many variables that make calculation of altitude a bit tricky and precise horizontal positioning aw well. In the Northern Hemisphere, aviation uses GPS and a system of ground based stations to improve accuracy. This is the Wide Area Augmentation System which we call simply WAAS. The ground based systems monitor minor variations in the geostationary satellites and transmit corrections. My Piper Archer 2 has a Garmin 430 which is WAAS certified and gives me accuracy vertically and laterally. It is this technology that is the basis for RNAV or gps approaches and flight. But even at the cost of $13K installed it is not perfect....which explains the tolerances for landing and other aspects of flight. With all the technology available today the accuracy is required to be no greater than a 25 foot error. GPS in its present state of evolution is not to the level you mentioned and will require much more to be so.

This might be interesting as it takes an entirely new approach to positioning but is still in the very very early stages of development. http://www.bbc.com/news/technology-18633917

http://www.bbc.com/news/technology-18633917