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# Calculating the distance between 2 points

## Calculating the distance between 2 points

(OP)
I'm much more of a software person, and in general this project is very much software heavy, but built on a hardware idea I'm not very educated on.

I'm looking for the types of available technology out there that can fit this problem.

A system in which a sensor can measure and store the distance of a bunch of receivers as the receivers move around in an area no further than 150 yards from the sensor.

The receivers must be small and basically weightless, but not nano size, just micro size. quarter to dime.

It must be able to work without LOS, but it in an open area, so no walls or anything.

It only has to be "relatively" accurate. Probably within a yard for a pre-alpha version.

For now I don't really care about cost, mostly availability as I'm just scoping things and researching.

I am just looking for technologies and articles about them, basically any pointing in the right direction anyone can offer so I can get better educated. Thanks for any help!

### RE: Calculating the distance between 2 points

Does it have to be in real-time?

Kinematic GPS-capable receivers can do this real-time.

Higher-end GPS receivers can also do this, but not real-time.

Differential GPS

### RE: Calculating the distance between 2 points

(OP)
It does not need to be displayed in real-time

If the movements happen and then 10 minutes late I have the data that is fine. I just meant it wasn't a stop and wait type thing, the receiver will be constantly moving so the data must be constantly collected while it's happening.

Isn't GPS overkill? Also I thought even with the higher end GPS it was still only within 7 feet or so.

There's nothing local that can do it better/more efficiently?

I'll checkout the Kinematic GPS, Thanks

### RE: Calculating the distance between 2 points

(OP)
I've stumbled across WiFi tags, they look to be a pretty good step towards what I'm looking forward, unfortunately looks like they're still kind of big. Anyone had any experience with them?

### RE: Calculating the distance between 2 points

At least for the aspect of the project that you've described, it's the software that is very nearly trivial and the hardware architecture and device selection that will probably be THE primary design issue.

Can you turn the system around so that the mobile units are the transmitters and the receivers are fixed? Your description of the non-realtime nature of the requirements implies that you could. It would probably be easier.

### RE: Calculating the distance between 2 points

Seems to me that the "project" is probably not about developing object locators.  But, if you are rolling your own, then it will become a "project" on its own, with its own issues and schedules unrelated to your primary "project."

Your time scale is awkward, since the postprocessing GPS' I'm thinking of are more like a day.

### RE: Calculating the distance between 2 points

If the mobile units would ping, then you could have several receivers triangulate on them based on time-of-flight. The receivers could also do them same thing amongst themselves to stay synchronized. Maybe use Barker Codes to narrow the pulse and improve SNR. But anyway you look at it, it's a very big development effort. Especially if you want the mobile units to be smaller than the battery inside them (requires bending the space-time fabric).

### RE: Calculating the distance between 2 points

(OP)
What there's no simple way to bend the space-time fabric? :)

### RE: Calculating the distance between 2 points

chirp ultrasonic goes for 30 meters or so depending on frequency / power / sensor size. sync up a few from a sensor and track them. GerwingR

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