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
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electronic distance measuring device
- Thread starter albor2974
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If so, I would think the military would be VERY interested in that! They could use it on bombs to not explode until they penetrated to a specifc room or level. Hmmm.....
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
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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
For the best use of Eng-Tips, please click here -> faq731-376
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i like your link with that radarvision jraef. It is a little more than i'm looking for though for sure and that of course would cost quite a lot. i would like to find an instrument that just takes a linear measurement but can go through walls and maybe your right that it would cost quite a bit. this instrument here i found is a measuring tape that uses sound waves and an infrared beam, but im pretty sure it doesnt see through walls.
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.
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.
Skogsgurra
Electrical
The Walkie-Talkie idea is not bad. It should be possible to do the measurement using "round trip time" for the radio waves. Cable length and cable failures are measured using TDR, aka Pulse Echo measurement aka Cable Radar.
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
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
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
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
1/8 inch through walls is not possible. The speed of EM propagation though dielectrics is different, so unless you have exact values, the errors will be quite huge.
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
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
As I understand the original post, the problem is to measure the outside dimensions.
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
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
I thought GPS accuracy was kept from being that close by the military. What do I know though, I didn't get my handheld GPS for christmas... ![[sad]](/data/assets/smilies/sad.gif "[sad] [sad]")
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
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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
jraef; Where have you been?![[hammer]](/data/assets/smilies/hammer.gif "[hammer] [hammer]")
At any rate you aren't going to get 1/8" accuracy. 4 get it.
Keith Cress
Flamin Systems, Inc.-
At any rate you aren't going to get 1/8" accuracy. 4 get it.
Keith Cress
Flamin Systems, Inc.-
Hi JRaef;
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
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
SA is based on the original notion of using the message chips of the GPS signal to measure time. Current models of high performance GPS use carrier pahse measurements to decrease real-time repeatability to less than several cm. With differential correction, the errors can be reduced to the mm range.
Perhaps the OP needs to be more specific as to what he's trying to do.
TTFN
Perhaps the OP needs to be more specific as to what he's trying to do.
TTFN
Hi IRstuff;
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
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
itsmoked said:
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!
From reading the original thread, check the Modsonic company and in particular UTG's or ultrasonic thickness gauges. The Edison series may or may not be what you are looking for but it fits in the palm of your hand and thus could not be that expensive.
Waross,
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
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
The only technology that I'm aware that should be able to meet this requirement would be: Ultra-Wide Bandwidth (UWB).
Wiki Link:
"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.
Wiki Link:
"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.
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