GPS device

[Mikebits]

I went for a ride along with a couple geologist to a site near one of San Diego's local fault lines. The purpose of the trip was to extract data from a GPS receiver/data recorder. They told me the device could track movements of a few centimeters, and they used it to monitor shifts in the fault.

I did a little searching for GPS devices, the best accuracy I could find was .5 meters. So how do you suppose they were able to get this kind of accuracy. Are there GPS chips with this sort of accuracy? Any links?

 

[dknguyen]

Resolution != accuracy

 

[Mikebits]

Resolution != accuracy

Umm, Okay.

 

[RadioRon]

**broken link removed**

Differential GPS (DGPS) rating is <0.45 m

 

[Mikebits]

Thanks Ron. Looks promising. I will check it out

 

[Mikebits]

My reason for being interested in GPS is this. I am trying to get one of my geology professors to take me on as an independent study student (Outside a classroom type thing). I proposed to him, that I wanted to study the effects of mass wasting (See link below) that occur in the desert in our area. This serves no real purpose, but for us geeky types, we just want to know.

My goal is to study how much material is moved, and how far, due to mass wasting over a period of time. I proposed this to my teacher that I could monitor this with GPS. My teacher told me if I could produce a design that could work (Produce documentation), that he would take me as an independent study student this fall.

My plan is rugged all terrain unit with the weight, shape and friction of a rock, placed in a undisclosed location (I don’t want anyone to find it). The device will measure the movements in the rock over a period of months. Of course I intend to make frequent download of data, and battery changes. It is about a 1 hour drive for me.

Mass wasting - Wikipedia, the free encyclopedia

 

[Torben]

Well, "a few" is hardly that specific a term. Perhaps they were trying to avoid saying "50-odd centimetres"?

At any rate, 0.45 m is hardly better than 0.5 m.

I wonder if it would be feasible to use 3 or more and average the outputs. Never tried; haven't even thought about it very hard.


Torben

 

[Mikebits]

I have always considered a few to mean two. Be that as it may <.45 seems to be the best number so far. Maybe the device the geologist were using had misleading literature like a 100W stereo amp the really puts out about 20W.

 

[Torben]

I have always considered a few to mean two. Be that as it may <.45 seems to be the best number so far. Maybe the device the geologist were using had misleading literature like a 100W stereo amp the really puts out about 20W.

I've always considered "a few" to mean "more than a couple but less than several". . .with "a couple" meaning two, and "several" meaning. . .um. . ."more than a few but less than lots". Uh. . .I'll stop there.

I suspect you may be right about the marketing literature thing.


Torben

 

[Mikebits]

But then again, the faults shift are only a few cm/yr, so .45m would hardly be useful at all. Hmm, I just wonder about this.

 

[Torben]

But then again, the faults shift are only a few cm/yr, so .45m would hardly be useful at all. Hmm, I just wonder about this.

Interesting. . .the Wikipedia entry on precise positioning with GPS says that some systems (even non-military) can get from 3 cm to 10 cm of resolution, but that the processing is slow enough that it's typically only used for "specialized surveying equipment".

Which sounds like it could include tracking plate movements. I wonder if it might also be used to track glacier movements.

At any rate, 3-10 cm is pretty darned impressive.


Torben

 

[Mikebits]

At any rate, 3-10 cm is pretty darned impressive.

Equally impressive is that they even have GPS that works indoors now.
Sensitivity of -158 dBM. This was unheard of 10 years ago.

 

[Torben]

Equally impressive is that they even have GPS that works indoors now.
Sensitivity of -158 dBM. This was unheard of 10 years ago.

Yow. Too bad Verizon doesn't offer cell data modems which can do that. It would make my job a lot easier.


Torben

 

[Mikebits]

See for yourself.
https://www.nemerix.com/products/NJ2020pb-12.pdf

 

[Diver300]

-158 dBm is loud compared to what some receivers can manage.

How about tracking signals 1000 times quieter than that?

**broken link removed**

 

[Mikebits]

If you notice, the spec is given in dBW not dBM. So -185 dBW is about -155 dBM. Still not shabby.