GPS – Global Positioning System
Developed for use by the U.S. military at the end of the cold war to track ICBM missiles.
Fully operational 1995 (selective availability turned off May 1, 2000)
Original Manpack developed for use by military
GPS – Global Positioning System
24 satellites orbit 22,200 km from earth, with five to eight satellites always visible from any point on earth
GPS receiver needs to make contact with signals from three satellites in order to find a location on earth
Contact with a fourth satellite allows for determination of elevation above sea level
GPS – Global Positioning System
Cost of GPS receivers from $100 for hand-held unit (accurate within 10 meters horizontally) to over $50,000 for research receivers (accurate within 1 cm horizontally)
Used extensively for marine and air navigation and mapping. Growing popularity of GPS use by hikers, hunters, fisherman, and gamers.
Scientific uses include atmospheric studies, plate tectonics, including mapping of volcanoes, and collection of coastline data
No cost to use the system
GPS – Global Positioning System
1.GPS technology relies on the use of satellites. 2.To locate a satellite, a GPS receiver measures
distance using the travel time of radio signals 3.To measure travel time, GPS needs very
accurate timing which it achieves with some tricks. • Along with distance, you need to know exactly where
the satellites are in space.• False code signals are created, one which the satellite
signals, and one that the GPS matches. When the two signals “line up”, the time is determined. The GPS emits a radio frequency, similar to the MHz on your radio, which increases the accuracy of the GPS.
• Finally you must correct for any delays the signal experiences as it travels through the atmosphere.
GPS – Global Positioning System
How Do You Use a GPS?
Each brand of GPS is set up differently.
At the Smith Center, we use Garmin etrex units.
GPS – Global Positioning System
Internal GPS Antenna
UP Button
DOWN Button
PAGE Button
POWER Button
LCD Display with Backlight
ENTER Button
GPS – Global Positioning System
The GPS receiver displays pages with separate functions. There are four main pages that you will be
using to navigate:
GPS – Global Positioning System
Let’s Get Started!
All GPS receivers operate on information gathered from satellites. In order to receive the satellite signals, you must be outside, away from any objects such as trees or overhangs that might block the signal. You need a clear view of the sky.
GPS – Global Positioning System
Step 1: Push and hold down the POWER BUTTON to turn the unit on. You’ll see the “Welcome” page for a few seconds, followed by the Satellite Page.
GPS – Global Positioning System
How do I know I’m ready to go?
When you see the “Ready to Navigate” message, you know the etrex has locked onto the satellite signal.
This must be displayed before you can begin using the GPS to navigate.
Signal strength bar will be filled in to indicate the GPS has locked onto signal.
GPS – Global Positioning System
Satellite Page Basics:
Two display pages:Normal Skyview that shows the satellites, satellite signal strength, and estimated accuracy.Advanced Skyview that shows you the numbered satellites being used, the proximity and horizon and sky overhead.
GPS – Global Positioning System
What does the MAP page do?
The map page shows where you are and uses an animated figure to show where you are actually going.
Waypoint names and symbols are also shown.
GPS – Global Positioning System
Map Page Basics:
You can change the map scale by pressing and holding the UP button to view a larger area, or the down button to view a smaller area.
You can change the scale from 200 ft to 800 miles to view your entire trip!
GPS – Global Positioning System
NAVIGATION PAGE BASICS
The Navigation Page guides you to your destination. It shows you your moving direction and speed. If you have a specific destination entered into the GPS, the page shows you the name of the location, the distance and displays a direction arrow that is shown in the compass ring.
GPS – Global Positioning System
NAVIGATION PAGE BASICS:
We’ll be using LATITUDE and LONGITUDE coordinates to describe locations.
Latitude measures distances North or South from the Equator (0°) towards the Poles. (90°)
GPS – Global Positioning System
NAVIGATION PAGE BASICS:
We’ll be using LATITUDE and LONGITUDE coordinates to describe locations.
Longitude measures distances West or East from the Prime Meridian (0° at Greenwich, UK).
GPS – Global Positioning System
The units that we will be using to measure are:Degrees (°)
North 39° Minutes ( ‘ )06And . . .
THOUSANDTHS of Minutes!
.582’
West 77° 06 .086’
GPS – Global Positioning System
MAIN MENU BASICS:
With the main menu you can create waypoints, routes, save and view your track logs. If you select MARK, you can mark your location as a waypoint.
GPS – Global Positioning System
GOING TO A WAYPOINT: Press the PAGE button and
switch to the MENU Page Press UP or DOWN and highlight
WAYPOINTS. Press ENTER.. Press the UP or DOWN button
and highlight the alphabetical tab for the waypoint. Press ENTER.
This will take you to a list of waypoints.
Highlight a waypoint, and press ENTER.
GPS – Global Positioning System
REVIEW WAYPOINT page appears. REVIEW WAYPOINT allows you to change coordinates, name, symbols, and delete waypoints.
On the REVIEW WAYPOINT page, press the UP or DOWN button and highlight GOTO, press enter.
GPS – Global Positioning System
GPS technology allows us to identify locations of specific trees
Useful in monitoring health of trees over time
Latitude and longitude coordinates are given for each tree location
GPS – Global Positioning System
GOING TO A WAYPOINT
It would be VERY difficult to use the GPS Unit by itself to find your way to your waypoint, so you will also need to know how to use. . .
GPS – Global Positioning System
A Map!
Use the map to look for landmarks, to stay on trails, to gauge distances, and to find your way back!
GPS – Global Positioning System
STEPS TO USING THE GPS: From the SATELITE page, press the PAGE button
until you come to the MENU page. Scroll down to WAYPOINTS, press ENTER. Scroll down to the tree waypoint entered. Press
ENTER. The REVIEW WAYPOINT screen will appear, select
GO TO, the COMPASS page will appear. Begin walking. The arrow will reorient in the
direction you should be walking if you could walk a straight line to your waypoint. You WILL need to adjust your line of travel to avoid obstacles and to remain on trails.
GPS – Global Positioning System
STEPS TO LOCATING THE TREE:
Follow the arrow and stay on trails to find desired coordinates. Remember that the GPS is only accurate within 10 meters. At this point you need to begin looking for the tree marker.
At this point, you will need to spread your group out and look for the tree marker.
GPS – Global Positioning System
ONCE YOU’VE FOUND THE TREE:
Use the dichotomous key to identify the tree.
Check your identification using a field guide to North Eastern trees.
Enter the next tree number and coordinates that you wish to locate as a GPS waypoint.
Continue to the next tree.
GPS – Global Positioning System
THINGS TO KEEP IN MIND:
Do not cross roads (except Meadowside Lane) Stay on trails. No bushwhacking! You may need to go around rocks or cross streams. Stay together – do not leave your group Use your map and compass in conjunction with the
GPS Respect the park. Take only your memories, leave
only your footprints.
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