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Re: [tracker2] How to deal with GPS drift with OT2?

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  • Bob Poortinga
    ... He is probably referring to the Static Navigation option that can be configured for SiRF III GPSs by using the SiRFdemo software. I wonder if Bernard has
    Message 1 of 16 , Nov 2, 2009
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      "Keith VE7GDH" <ve7gdh@...> writes:

      > What do you mean by "Static Navigation"?

      He is probably referring to the "Static Navigation" option that can be
      configured for SiRF III GPSs by using the SiRFdemo software.

      I wonder if Bernard has tried "Track Smoothing" or increasing the acceptable
      minimum signal satellite strength and turning off degraded mode and dead
      reckoning?

      --
      Bob Poortinga K9SQL <http://www.linkedin.com/in/bobpoortinga>
      Bloomington, Indiana US
    • Scott Miller
      ... If you have AUTOSAVE on in profile 2, you can set profile 2 to BMODE FLOW, or anything but AUTO, and it ll lose GPS lock and save the last position.
      Message 2 of 16 , Nov 2, 2009
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        > I was wondering if using the AUTOSAVE followed by POSITION X,Y commands
        > when entering Profile 2 would let the OT2 save the last known fix rather
        > than X,Y if X,Y are given special values like 0,0 or illegal values.

        If you have AUTOSAVE on in profile 2, you can set profile 2 to BMODE
        FLOW, or anything but AUTO, and it'll 'lose' GPS lock and save the last
        position.

        Scott
      • James Ewen
        ... Take a look at your surroundings... If you park the car nose in, you ve got a wall and car port with a roof that looks to be at least 9 feet high right in
        Message 3 of 16 , Nov 2, 2009
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          On Mon, Nov 2, 2009 at 1:43 AM, ki6tsf <ki6tsf@...> wrote:

          > I posted a pict showing GPS drift at http://groups.yahoo.com/group
          > /tracker2/photos/album/411553253/pic/812065518/view?picmode=
          >&mode=tn&order=ordinal&start=1&count=20&dir=asc
          >
          > That's not very nice for a portable or mobile digipeater.

          Take a look at your surroundings... If you park the car nose in,
          you've got a wall and car port with a roof that looks to be at least 9
          feet high right in front of the car. Behind you is a 3 storey
          building, maybe 30 feet away. At least you didn't park under the tree.
          (Gotta love Google Streetview!)

          You'll have blocked views of the horizon for most of the azimuth
          around you. The 3 storey wall behind you will probably bounce signals
          like crazy, leading to position accuracy problems with the GPS.

          If you put a relay in the data line between the GPS and the OT2,
          triggered by the accessory line in the vehicle, you will basically
          disconnect the GPS from the OT2. Configure the OT2 to use the last
          known position. Leave the GPS power on constant 12 volts, and the GPS
          will always be active, leading to faster position acquisition when you
          start the vehicle. (By faster, I mean instantaneous, unless you have
          parked in an underground or covered parking area)

          James
          VE6SRV
        • ki6tsf
          Hello, Thank you to all who replied and for all the suggestions! Yes, Static Navigation is a feature built-in in SiRF III-based GPSs and I used SiRFDemo to set
          Message 4 of 16 , Nov 2, 2009
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            Hello,

            Thank you to all who replied and for all the suggestions!

            Yes, Static Navigation is a feature built-in in SiRF III-based
            GPSs and I used SiRFDemo to set it. It is supposed to eliminate
            drift. I'll check with SiRF directly if they can advise how
            to tune it.

            Actually yes, I enabled Track Smoothing too and that didn't help.
            I have not raised the satellite signal strenght threshold, this is
            next on my checklist.

            I set degraded mode and dead reckoning on (I found it really cool
            to have a GPS receiver that supports those modes!!!). I'll have
            to try with these features turned off.

            Anyways I hope a combination of all or some of the suggestions
            received on this newsgroup will solve that drift problem!

            Thanks to all,

            Bernard KI6TSF

            --- In tracker2@yahoogroups.com, Bob Poortinga <bobp+yahoo@...> wrote:
            >
            > "Keith VE7GDH" <ve7gdh@...> writes:
            >
            > > What do you mean by "Static Navigation"?
            >
            > He is probably referring to the "Static Navigation" option that can be
            > configured for SiRF III GPSs by using the SiRFdemo software.
            >
            > I wonder if Bernard has tried "Track Smoothing" or increasing the acceptable
            > minimum signal satellite strength and turning off degraded mode and dead
            > reckoning?
            >
            > --
            > Bob Poortinga K9SQL <http://www.linkedin.com/in/bobpoortinga>
            > Bloomington, Indiana US
            >
          • k7ybz
            When I originally read your post I was thinking unit sensitivity of the BR-355 compared to Garmin pucks. I had remembered reading the sensitivity of the BR-355
            Message 5 of 16 , Nov 2, 2009
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              When I originally read your post I was thinking unit sensitivity of the BR-355 compared to Garmin pucks. I had remembered reading the sensitivity of the BR-355 as being around -160 and Garmin around -185.
              Then I went back and looked at the specs again and noticed Garmin specifies their sensitivity as dBW and everyone else specifies it in dBm. There in lies the difference (and another Garmin marketing ploy): 0dBW = +30dBm.

              Ahhh, the numbers game!

              I may have missed where the puck was placed, but the puck is much better off on the roof of the vehicle than on the dash. On some units, the magnet can be removed and mounted directly to a surface. I did not investigate this for your particular unit though.

              Larry
              K7YBZ

              --- In tracker2@yahoogroups.com, "ki6tsf" <ki6tsf@...> wrote:
              >
              > Hello,
              >
              > Thank you to all who replied and for all the suggestions!
              >
              > Yes, Static Navigation is a feature built-in in SiRF III-based
              > GPSs and I used SiRFDemo to set it. It is supposed to eliminate
              > drift. I'll check with SiRF directly if they can advise how
              > to tune it.
              >
              > Actually yes, I enabled Track Smoothing too and that didn't help.
              > I have not raised the satellite signal strenght threshold, this is
              > next on my checklist.
              >
              > I set degraded mode and dead reckoning on (I found it really cool
              > to have a GPS receiver that supports those modes!!!). I'll have
              > to try with these features turned off.
              >
              > Anyways I hope a combination of all or some of the suggestions
              > received on this newsgroup will solve that drift problem!
              >
              > Thanks to all,
              >
              > Bernard KI6TSF
              >
              > --- In tracker2@yahoogroups.com, Bob Poortinga <bobp+yahoo@> wrote:
              > >
              > > "Keith VE7GDH" <ve7gdh@> writes:
              > >
              > > > What do you mean by "Static Navigation"?
              > >
              > > He is probably referring to the "Static Navigation" option that can be
              > > configured for SiRF III GPSs by using the SiRFdemo software.
              > >
              > > I wonder if Bernard has tried "Track Smoothing" or increasing the acceptable
              > > minimum signal satellite strength and turning off degraded mode and dead
              > > reckoning?
              > >
              > > --
              > > Bob Poortinga K9SQL <http://www.linkedin.com/in/bobpoortinga>
              > > Bloomington, Indiana US
              > >
              >
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