Part II: Section B
Using GPS Technology
3.1 Basic Operations

Basic operations assuming that the Magellan SporTrak Pro receiver has been initiated (Figure IIB-2).

Figure IIB-2: Basic operation key.

Setting up Coordinate System and Datum

The Magellan SporTrak Pro receiver allows one to get the position fix in two different coordinate systems and datums.

To avoid confusion, for now we will worry only about the primary screen.

Recommended setup: UTM NAD 1983 Zone 10 N.

How to Check or Change the Coordinate Systems
  • Turn the SporTrak on by pressing Power
  • Press Enter to accept the warning stating that data is provided for reference only
  • Press on Menu
  • First thing listed is coordinate System Coord System
  • Selected by pressing Enter
  • Choose Primary
  • Highlight UTM
  • Press Menu again
  • Choose Map Datum (second option after Coord System)
  • Press Enter
  • Choose Primary
  • Highlight North American Datum 1983 (NAD83)
  • Press Enter

Getting a Position Fix

Because the receiver obtains information it needs from satellites orbiting the earth, the antenna needs to have a relatively unobstructed view of the sky. This allows the receiver to choose from all satellites currently available.

Before accepting any final position, you must wait for the WAAS signal. This may take a few minutes, and it usually is necessary only for the first point, providing that you do not turn off the receiver between points. Information will be stored temporarily and is readily available for computing averages for the next stationary location. If you turn off the receiver between points, you may have to wait until all satellites are locked and WAAS is enabled again.

Position screens 1 and 2 display your present position using the coordinate systems that you have selected in the setup. The screen on the left is shown when you are stationary (finding a fixed point); the one on the right is displayed when you are moving. This screen shows all of the basic position, time, and satellite information. In addition, current navigation information is shown in the bottom half of the screen.

 When you are acquiring photographs in the field, you will record on your data sheet the easting (X), the northing (Y), and the time. The elevation (Z) is not very accurate using these hand-held GPS devices and it is not very important to us. You also must record ancillary information that is found on the data form corresponding to the photo number. Remember, information related to your location on the field is displayed in screen 1 (top part of the display). Make sure screen 2 (middle part of the display) displays the WAAS enabled. We recommend that you spend at least 1 minute at each location. The GPS will average all the positions collected and display the WAAS Avg. and 00:01:08 in screen 2. The value 10 at the top of screen 1 refers to zone 10. You do not need to record this number because it is the same for all western Oregon (between 120ºW and 126ºW).

<< previous page  
1. What is GPS?
2.How Does GPS Work?
3. Instuctions for Using SporTrak GPS Recievers
- 3.1 Basic Operations
- 3.2 Display
4. Performance Testing
5. Glossary
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