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7.2 GPS Use for GIS Application


Set Up Before Going To The Field:
  • Make sure fresh batteries are loaded and extra sets available.
  • Transfer background maps using MapSource for the area of mapping (if available).
  • Turn unit on to initialize and acquire satellites if you are in a new area or haven’t used the unit in at least a week. This may take as long as 20 minutes in the open, away from buildings, canopy and obstructions.
  • Download and clear old Waypoints and Tracks from memory. Download any data you don’t need, make a copy and clean up waypoints in list and clear all saved tracks and active tracklogs.
  • Turn off active tracklog. Set tracklog to the preferred Collection method (Time is best) and an appropriate logging rate for the data collection. 5 seconds works for most walking collection, but keep in mind the total storage capacity of the GPS.
  • Ensure Simulator Mode is not ON when collecting data.
  • Set unit time and date (Ensure Daylight Savings Time if needed).
  • Check Interface Protocol is set properly.
  • Set the Coordinate System (UTM or LAT/LONG) and Datum to ensure compatibility with any written coordinates you may need to navigate to or Map.
  • Set Heading to Magnetic or True. If set to true, ensure compass has same declination.

Field – GPS Data Collection:
  • Hold GPS antenna away from body with antenna up. Better yet, hold at, or above the head. Purchase an external antenna to free hands if needed or for better reception in vehicles.
  • Mark (save) waypoints for point locations at beginning and ending of track log collections. Writing down a position is just backup.

Waypoints:
  • Collect all waypoints in Averaged Position mode if you are standing still (when possible and if your receiver has that capability). Minimum of 10 positions, maximum of 20 minutes. Somewhere in between is enough to generate a quality position in most cases.
  • Collect an instantaneous waypoint only when moving or in a hurry (or if using the eTrex line).
  • Edit default waypoint numbers to letters or words that are more descriptive or make good field notes to ensure you remember what features are represented by which numbers.
Tracklogs:

  • Use “Stop when Full” or “Fill” Record Mode rather than wrap to prevent overwriting tracklog points when Active Tracklog becomes full.
  • Turn on Active Tracklog at start location and immediately begin moving.
  • Stop Active Tracklog when movement is stopped temporarily or when mission is finished.
  • Always Stop Active Track just shy of starting point when collecting an area (polygon). Overlapping with start point makes conversion to GIS more challenging.
  • Always turn Active Tracklog to OFF when finished collecting or turn receiver off to avoid collecting unwanted positions after mission is complete.
  • Use caution when saving an Active Tracklog. Garmin will generalize any active track to save space, thereby degrading data. If you save a track log and clear the active track, you won’t be able to go back to the more detailed track log positions.

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