gis, gps and field data collection
TRANSCRIPT
8/14/2019 GIS, GPS and Field Data Collection
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GISGIS
GPS, Field DataGPS, Field Data
CollectionCollection
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Good Satellite GeometryGood Satellite Geometry
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Sources of Error Sources of Error
Poor Satellite GeometryPoor Satellite Geometry
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Sources of Error Sources of Error Poor satellite elevationPoor satellite elevation
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Sources of Error Sources of Error Too few SatellitesToo few Satellites
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WAASWAAS
• Wide Area AugmentationSystem
• 3m accuracy 95% of the time
• Developed by FAA and DOTfor precise flight approaches
• 25 ground reference stations,
2 master control center one on
each coast, 2 satellites
centered over the equator
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Field PreparationField Preparation
Why are you collecting data?Why are you collecting data?
• Is this a new survey?
• Will it be used with existing data?
• Are you going to make a map?
All important questions to ask because before
you collect any data you need to choose what
Coordinate System to set the GPS to.
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GeographicGeographic
• A Geographic coordinatesystem documents the shape of
the earth.
• Units are stored in Latitude and
longitude degrees.
Projecte
d•A projected coordinate systemtakes a three-dimensional position
on the earth’s surface and
translates it to a flat surface.
•Types of projected units: UTM,
State plane, British Grid…..
The raw signal from the GPS Satellites is
WGS 84.
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How do you choose which systemHow do you choose which system
to use.to use.
1. If this is a new site new data start
collection in WGS 84 (Raw GPS Signal)
2. Set your GPS unit to the coordinatessystem of the existing data.
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Garmin BasicsGarmin Basics
•Pages
•Menus
•Functions & Dialog Boxes
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Garmin EtrexGarmin EtrexZoom in / Zoom Out:
Press and hold to zoom on the map page
Power/Backlight Button
Page:
Press and release to cycle through main pages
Click Stick:
Five position switch..
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Scroll Through The Different ScreensScroll Through The Different Screens
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Main Menu PageMain Menu Page
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First thing firstFirst thing first
Set up your GPS unitSet up your GPS unit
Geographic
or Projected Units?
What is the difference?
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What is a Datum?How do I know which one to use?
Found on all USGS Maps
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Creating a WaypointCreating a Waypoint
Make sure you hit
“OK”
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Navigation FunctionsNavigation Functions
“Goto: as the crow flies
Track: tracks your exact path
Route: a path to a destination using
waypoints or markers.
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TracksTracks
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GPS Exercise 1GPS Exercise 1
First enter your waypoint.
Then hit Goto
Navigate with theCompass
Or with the
Map page
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Waypoint creationWaypoint creation
• Shortcut for on-the-spot marking:
Hold down the toggle button/joystick for a
couple of seconds to capture your current
position. Enter a name for the point
• To enter a distant waypoint, go to Main
Menu: Mark