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Regarding Garmin Binary Protocol

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  • Bob Poortinga
    There have been many discussions in the past regarding breadcrumbs (duplicate waypoints) in Garmin GPS s. I found a copy of the 2006 version of the Garmin
    Message 1 of 1 , Sep 14, 2010
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      There have been many discussions in the past regarding "breadcrumbs"
      (duplicate waypoints) in Garmin GPS's.

      I found a copy of the 2006 version of the Garmin Device Interface Specification
      (Garmin Binary Protocol) at:

      <http://gpsd.berlios.de/vendor-docs/garmin/IntfSpec.pdf>

      and here it is from the horse's mouth:

      ------------------------------------------------------------------------
      5.5 Device Overwriting of Identically-Named Data

      When receiving data from the host, some devices will erase identically-named
      data and replace it with the new data received from the host. For example,
      if the host sends a waypoint named XYZ, these devices will overwrite the
      waypoint named XYZ that was previously stored in device memory. No warning
      is sent from the device prior to overwriting identically-named data.

      Other devices have special handling for identically-named waypoints. These
      devices may compare the position of the incoming waypoint with the position
      of the existing waypoint, for instance (Note: altitude is ignored during the
      comparison). If the positions match, the device will erase the identically-
      named waypoint and replace it with the new waypoint received from the host.
      If the positions differ, the device will create a new, unique name for the
      incoming waypoint and preserve the existing waypoint under the original name.
      THERE IS NO MECHANISM AVAILABLE FOR THE HOST TO DETERMINE WHICH METHOD A DEVICE
      USES FOR WAYPOINTS (OVERWRITING VS. UNIQUE NAMING).
      ------------------------------------------------------------------------

      There you have it. Garmin says some devices do and some don't and that's
      the way it is.

      --
      Bob Poortinga K9SQL <http://www.linkedin.com/in/bobpoortinga>
      Technology Service Corp. <http://www.tsc.com>
      Bloomington, Indiana US
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