NR 322: GPS and GIS

Jim Graham

Spring 2010

GPS Manuals

Global Positioning System (GPS)

• Hand-held receiver

• Find your position

• Guide you to a position

Inexpensive

• Bring extra batteries!

• Works inside a plastic bag

Garmin

Natural Resource GPS

• More rugged

• Longer battery life

• More accurate

Trimble

GPS Network

• Utilizes a network of 24 satellites that transmit precise microwave signals

Global Position System

Every point on circle is a possible receiver location

Satellite 1 Location

Receiver Location?

Receiver Location

How do GPS units work?

Satellite 1 Location Satellite 2 Location?

?

How do GPS units work?

Satellite 1 Location Satellite 2 Location

Satellite 3 Location

Known Receiver Location

How do GPS units work?

Accuracy

• Standard GPS1

– Theoretical Limit: 30 centimeters– Typical: 15 meters (45 feet)

• Differential GPS2

– Predicted: 0.67 m per 100 km– Measured: 0.22 m per 100 km

2. http://en.wikipedia.org/wiki/Global_Positioning_System

1. Statement by the President regarding the United States' Decision to Stop Degrading Global Positioning System Accuracy". Office of Science and Technology Policy (May 1, 2000). Retrieved on 2007-12-17.

GPS Use

• Power

• Page

• Up

• Down

• Enter

• Find

Up

Down

Enter

Page

Power

Up

Down

Find

Page

Power

Thumb Stick

LCD Display

LCD Display

Main Pages

• Satellites

• Trip Computer

• Map

• Compass

• Main Menu

Menu

• Mark = Point

• Waypoint = Point

• Route = Polyline

• Track = Polyline

• Setup

Set the projection and datum!

“Navigating”

Satellite Page

• Number of satellites

• Accuracy

• Position!

Compass

• Only works when moving!

Map

• More expensive models can show topos

Trip Odometer/Computer

• Shows the elevation

GPS with GIS

• Digitize with:– Way points: points– Tracks: polyline– Route: polyline

• Way Points:– Tree locations– Wildlife sign– Campsites

• Tracks:– Record where you’ve

been– Trails– Animal tracks– Streams

• Routes:– Create a route to

follow– Same as tracks?

DNRGarmin

• Free software from Minnesota Department of Natural Resources– Trimble’s solution is different!

• Standalone or plug-in

• Need special serial cable– https://my.garmin.com/shop/shop.do?pID=6

54– Search for “garmin gps serial cable”

Downloading data

• Install DNR Garmin

• Connect Serial cable to the computer

• Connect serial cable to the connector behind the rubber flap on the top of the back of the GPS (some have small USB connectors now)

• Turn on the GPS!

• Open DNR Garmin

Download Waypoints

• Save to Shapefile

Troubleshooting

• GPS:– DNR Garmin GPS Menu

• Computer:– Control Panels -> Admin Tools -> Computer

Management -> Device Manager -> Ports -> Communications Port -> Properties -> Port Settings

• Make sure Baud rates match – 9800 is Garmin default

• Make sure ports match– Should be Port 1 for serial

Easy GPS

• Tiny, easy to use GIS package

• Free

• EasyGPS.com

• Garmin, Magellan or Lowrance GPS

• Exports to “GPX” format