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Distance measurement

Discussion in 'Electronic Design' started by GeoSound, Jun 12, 2008.

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  1. GeoSound

    GeoSound Guest

    Trying to conger up a means to measure distance from a radio tower.
    Thought that maybe one could capture the time of reception of the direct
    wave then from a reflected wave at known distance from the antenna doing
    the direct capture measure the difference (shift) to know the distance
    from the tower. Without a unique signature, I am presuming that a
    computer program could be written to find where the 2 signals should
    have matched in order to find the difference. Is this a viable idea or
    have I slipped over the edge or forgotten basic physics? Dale
     
  2. PeterD

    PeterD Guest

    I think you slipped over the edge!

    I know you can measure the distance to the reflector that way, and I
    supose if you know the distance to the reflector, and the distance
    from the relector to the source you can then comput the final leg of
    the triangle...
     
  3. PeterD

    PeterD Guest

    Actually if you know the location of the transmitter and the
    destination, any good GIS software will tell you the straight line
    distance.
     
  4. mpm

    mpm Guest

    What exactly are you trying to do?
    I am assuming you (the device?) is mobile, and you want to know how
    far you (the device?) is from one or more particular towers.
    Since "towers" are almost always stationary, if you (the device) are
    also stationary, then some simple math will take care of the request.

    For cell phones, many carriers use a technique called time difference
    of arrival (TDOA).
    Do a Google search.

    You would have to do this in reverse, and it might not be possible
    given the information you will likely have at your disposal.
    You might be able to do something with Loran or GPS, etc...??

    How much accuracy do you need? -mpm
     
  5. TDOA will show bearing to the propagated wave (direction), but not
    distance.

    Frank
     
  6. JosephKK

    JosephKK Guest

    You have that backwards. It shows distance not direction. Phase
    difference can be used for direction at those frequencies.
     
  7. JosephKK

    JosephKK Guest

     
  8. JosephKK

    JosephKK Guest

    Really? How/why does the time TDOA data result in hyperbolic curves?
    As i said, TDOA does not give bearing, for two data values, but a
    line/curve of delta distance. You correctly pointed out comparing
    TDOA from three or more points can produce 2-d (or spherical)
    location.
    For any doublet of two transmitters - one receiver or vice versa, it
    gives delta distance, not bearing.
    I have no clue as to your age, but i am of quite an age. I have been
    conversant with the theory and practice of Loran, DME, TACAN, VOR
    VORTAC, IFF, 2-d and 3d radar, and sonar for decades. Please do not
    be too dismissive of me. I might consider it impolite.
     
  9. JosephKK

    JosephKK Guest

    I considered it a possibility.
    Dead on. Did not mean to be sloppy though. But may have went
    overboard in oversimplifying for OP.
     
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