gis, gps and field data collection

8/14/2019 GIS, GPS and Field Data Collection

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GISGIS

GPS, Field DataGPS, Field Data

CollectionCollection



Good Satellite GeometryGood Satellite Geometry



Sources of Error Sources of Error

Poor Satellite GeometryPoor Satellite Geometry



Sources of Error Sources of Error Poor satellite elevationPoor satellite elevation



Sources of Error Sources of Error Too few SatellitesToo few Satellites



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



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.



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.



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.



Garmin BasicsGarmin Basics

•Pages

•Menus

•Functions & Dialog Boxes



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..



Scroll Through The Different ScreensScroll Through The Different Screens



Main Menu PageMain Menu Page



First thing firstFirst thing first

Set up your GPS unitSet up your GPS unit

Geographic

or Projected Units?

What is the difference?



What is a Datum?How do I know which one to use?

Found on all USGS Maps



Creating a WaypointCreating a Waypoint

Make sure you hit

“OK”



Navigation FunctionsNavigation Functions

“Goto: as the crow flies

Track: tracks your exact path

Route: a path to a destination using

waypoints or markers.



TracksTracks



GPS Exercise 1GPS Exercise 1

First enter your waypoint.

Then hit Goto

Navigate with theCompass

Or with the

Map page



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

gis, gps and field data collection

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