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gps vehicle tracking

Discussion in 'General Electronics Discussion' started by Laxmee, Jun 19, 2014.

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  1. Laxmee

    Laxmee

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    Jun 19, 2014
    How can we know that the gps receiver is tracking the data?Are the NMEA format of data received by the gps receiver as soon as it is turned on?we are using GT320R gps module.
     
  2. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    All GPS chipset need to update the ephemeris and almanac data. It needs this before it can relay PVT data. Hot starts can be active within 1 second after being turned of for say maximum of 2 hours after an initial fix but cold starts might take up to 35 seconds for say the SiRF star family of chipsets.

    Adam
     
  3. Laxmee

    Laxmee

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    Jun 19, 2014
    how is almanac and ephemeris data related to nmea 0183 format?how is the nmea format of data obtained from gps receiver? Can we obtain this format of data in hyperterminal?
     
  4. davenn

    davenn Moderator

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    Sep 5, 2009
    The data is uploaded to the GPS satellites by the satellite operators, it is then downloaded to any GSP receivers receiving the GSP signals. With out that updated data the GSP location and timing data would be inaccurate

    it is a serial output from the GPS receiver and can be decoded with software. There are lots of PIC micro circuits and code available on the net for displaying NMEA info

    cheers
    Dave
     
  5. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Thanks Dave
     
  6. Laxmee

    Laxmee

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    Jun 19, 2014
    Thanks a lot,
     
  7. Laxmee

    Laxmee

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    Jun 19, 2014
    In GPS gt320r what is meant by its features:
    1.12 parallel channel GPS receiver
    2. 4100 simultaneous time-frequency search bins
    3. -140dBm acquisition sensitivity
    4 -150dBm tracking sensitivity
    5. 5m CEP accuracy
    please explain each point if possible
     
  8. davenn

    davenn Moderator

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    Sep 5, 2009
    This is the first question you need to ask since there are two different interpretations of the answer. One is, any receiver capable of tracking 12 satellites. The second answer is a receiver having dedicated hardware to receive 12 channels simultaneously, also known as a twelve channel parallel receiver.

    not familiar with this term, but it related to the speed of satellite acquition

    These are both an indication of the receiver sensitivity .... anything below -130dBm is VERY sensitive
    its telling you that it needs a signal of at least -140 dBm to be able to acquire a given satellite but once acquired,
    the signal can drop another 10dB in strength before it will drop out.
    On the freq that GPS uses the noise floor will be somewhere around -150 to -160 dBm


    that's just telling you the positioning accuracy, you wont get better than a positioning of 5m


    with the GPS gear I service, we get down to 2 - 3 mm ( millimetres) of accuracy

    cheers
    Dave
     
  9. Laxmee

    Laxmee

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    Jun 19, 2014
    Thank u very much.
     
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