electronic distance measuring device
electronic distance measuring device
(OP)
does any one know of a tool that will accurratly measure the distance through walls. some type of an electronic measuring tape? Where one end could be placed in the house and the other could be walked around the house taking measurements through the walls. Something accurate to an eigth of an inch and that preferrably cost only a couple of thousand bucks or less. thanks





RE: electronic distance measuring device
I have not heard of any nor can I think of even how that would be done. Maybe microwaves, I'm thinking of something like ground penetrating radar. But how would it know where to stop if it can penetrate a wall? You would need to place a target of some dissimilar / impenetrable material maybe. Still, I seriously doubt it would cost that little.
JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
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RE: electronic distance measuring device
All the good ideas are already taker.
http://www.radarvision.com/
RE: electronic distance measuring device
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Im looking for an instrument in where one could put one part of it in one room, then the other in the next room over and take an accurate distance measurement between the two devices. Like a set of walkie talkies that will tell the distance between the two radios. Maybe it is too expensive. Does anybody have any ideas or know of such an instrument.
RE: electronic distance measuring device
But cable measurements are difficult to make down to even a foot. So 1/8 of an inch will probably not be possible. At least not today (or tomorrow). Radio waves also travel with different speeds in different media. Walls slow them down a bit and that may be another complication.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: electronic distance measuring device
RE: electronic distance measuring device
respectfully
RE: electronic distance measuring device
GPS in the building is pretty tricky for the same reason. In addition, there'll be tons of multipath.
You're best bet is some scheme using a theodolite and a accurate laser rangefinder. Again, nontrivial, but it only requires simple trig and line of sight through doors.
TTFN
RE: electronic distance measuring device
GPS has been used for some years for land surveys. One technique to avoid the need for differential is to read both GPS units simultaneously.
There was a unit in use for land surveys that had a base unit at a known location which tracked and recorded the Selective Availability error. The field units would record the co-ordinates of a point and the time of the reading. When the field unit returned to the office, The computer would look up the magnitude and direction of the selective availability error for each reading and make the corrections.
Do some checking on what is currently available in the way of GPS for land surveys.
respectfully
RE: electronic distance measuring device
Not a bad concept, but maybe simpler than trying to bounce lazer beams around corners would be to string a tight wire and use a TDR, then do the trig work to extrapolate a distance. If it's more than one corner though, I wouldn't want to be the guy with the calculator... ugh!
JRaef.com
"Engineers like to solve problems. If there are no problems handily available, they will create their own problems." Scott Adams
For the best use of Eng-Tips, please click here -> FAQ731-376
RE: electronic distance measuring device
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At any rate you aren't going to get 1/8" accuracy. 4 get it.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: electronic distance measuring device
my understanding is that the military uses a technique called selective availability to dither the signal. I understand that it is not inaccuracy but induced error.
Sort of like measuring a long board with a tape measure when the guy on the other end doesn't put the end of the tape measure right on the end of the board.
There are techniques to cancel out the error. Differential transmitters are one technique. These are used to broadcast a correction signal to aircraft near airports.
At one time land surveyors used real time error tracking and later made the corrections in the office, as I tried to describe earlier. I haven't spoken with a surveyor for some years now and I don't know if this technique is still in use.
The point is that civilian GPS will very accurately indicate the wrong spot. There are tecniques to correct this induced error.
If the GPS told us that we were 70 feet below sea level when we were standing on the dock all the GPS sets in camp would indicate 70 feet below sea level, and if you then climbed up on a flying bridge the GPS would indicate that you were now only 65 feet below sea level.
Respectfully
RE: electronic distance measuring device
Perhaps the OP needs to be more specific as to what he's trying to do.
TTFN
RE: electronic distance measuring device
I was under the impression that two GPS units that were capable of mm resolution with differential correction would still agree with each other within mm without differential correction but the absolute position may be off a little. That is you can achieve relative accuracy without differential correction but need the differential for absolute accuracy.
Do I have this right?
Thanks
Respectfully
RE: electronic distance measuring device
Like I said, not a GPS geek yet. I asked Santa for one, didn't get it. I'm a kinetic learner so I figured I'd bone up on the technology once I had one in my hands. All I know about them now (other than ads) I learned in 2000 on a cross country flight sitting next to a guy who worked for NOAA and had one in his laptop. He was tracking our flight progress on his screen, then using a Terra Server map (at that point virtually unknown as well) to zoom in on features we could see out the window. He told me that the system he had was (at that time at least) not "street legal". From that Clinton speech you posted, it must have become so right after that!
RE: electronic distance measuring device
RE: electronic distance measuring device
Unless the receivers are specifically designed for DGPS, it's not possible to correct. If you do not know which satellites were used with each erceiver, correction is impossible. Morever, if they're not using carrier phase detection, the error is still on the order of about a meter. A high performance carrier phase detecting receiver using both L1 and L2 bands can get submeter performance, standalone.
Currently, SA is not enforced, but the chip frequency of the military L2 band is 10 times better than that of the L1 civilian band. The FAA has two geosync that provide a wide area augmentation service (WAAS), that does the crude equivalent of DGPS, but the error correction bring the uncertainty only down to a few meters.
TTFN
RE: electronic distance measuring device
Wiki Link: http://en.wikipedia.org/wiki/Ultra-wideband:
"One of the valuable aspects of UWB radio technology is the ability for a UWB radio system to determine "time of flight" of the direct path of the radio transmission between the transmitter and receiver to a high resolution."
"...UWB is also used in 'see-through-the-wall' precision radar imaging technology, precision positioning and tracking (using distance measurements between radios)..."
If you're starting from scratch, then unit price would depend on quantity of course.
RE: electronic distance measuring device
RE: electronic distance measuring device