A Lidar survey done In Sri Lanka done by survey department has experienced a disturbance of GPS signal attached to the unit inside flight.The area is in hill country,there is a Radar station established for aviation purposesAnd telecom towers around the area.This was done by JAICA,they have done several runs but GPS signals not recorded even after switching off the radar station,as Lidar will not work properly without GPS recording,they have cancelled that area and silected another area.According to the department sources stil not aware about this finomina.If engine represented such incident?In case this type of disturbance exist will it not effect our GPS surveys on ground?That clearly highlights the importance of ground survey methods though technology bypasses us.

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  • Land Surveyor

    Hi Lalith

    Two incidents I can remember back during mid-1995 in Oman (using Leica 300).

    Near Muscat (Oman) airport it was possible to receive GPS signals only at certain times.

    In the desert around Nimr (Oman) no GPS signals close to a Radar station.

    Believe James Starbuck’s reply is the answer!

    Cheers

    Thilak Balachandra

    • Then how can be believe the data gathered by GPS for controles?
      Are we to check those with ground survey mathods?
      Lalith
      • Land Surveyor

        Lalith

        Surveying being a technique, that people use equipment for measurements to determine positions :

        Human, equipment and environmental errors can occur during measurements.

        One has to have sufficient cross checks to minimize / eliminate errors.

        As Lidar depend on GPS, it is unable to operate if there are no signals. Need to use an alternative methods.

        Regards

        Thilak

  • Land Surveyor

    Hi,

    I remember doing survey work at a small local airfield in England back in the 90s. We were using Trimble GPS and it was behaving very strangely, so much so that we couldn't work. We guessed the radar might have something to do with it since it was visible and spinning round. We asked if it could be turned off since there was no activity, it was a Sunday and there was nothing happening that day so they were ok with that. When it was turned off everything was fine.

    I have always wanted to find out if this is a real issue or not.

    Regards,

    James.

  • Land Surveyor

    Lalith

    That sound very extrage to me.

    We provide LIdar service anually to an oil company, and the their cans pass near inside aor principal aerport.

    Never experimet that issue.

    Mast be another problem.

    Best

    • Hi Javier

      May be something like " Bemuda Triangle"

      I need feed back from survey department ,it is interesting to know,

      Regards

      Lalith
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