Cheap GPS (From xkcd)

Cheap GPS(From xkcd.com)

Global Positioning

SystemAnd Tree

Identification

Global Positioning System and Tree IdentificationPresented at the MAEOE Conference, 02/06/10

by: Lathrop E. Smith Environmental Education CenterMontgomery County Public Schools

Introduction: Who am I?

Rationale: STEM and NCLI

Outline: Lots of Directions, Outside, Back Inside to Wrap Up

Introduction: Who am I?

Mark Granger – L. E. Smith Center MCPS

[email protected]

Rationale: STEM

Science Technology Engineering and Math

New emphasis in MSDE and at the Federal Level

Rationale: NCLI – No Child Left Inside

Maryland Partnership for Children in Nature

Also Federal support

Lots of Directions, Outside, Back Inside to Wrap Up

A Little Tree Vocabulary. . .


Coniferous or Deciduous?


Alternate or Opposite?


Simple or Compound?


Lobed? Serrated? Margins?

What is GPS and how does it work?

GPS - Global Positioning System

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


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 compute a location on earth

Contact with a fourth satellite allows for the computation of time.



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


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.



How Do You Use a GPS?

Each brand of GPS is set up differently.

At the Smith Center, we use Garmin etrex units.


Internal GPS Antenna

UP Button

DOWN Button

PAGE Button

POWER Button

LCD Display with Backlight

ENTER Button


The GPS receiver displays pages with separate functions. There are four main pages that you will be

using to navigate:


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.


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.


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 satellites’ signals.

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 a signal.


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, their signal strength, and their position in relation to you.


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.


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!


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 it displays a direction arrow that is shown in the compass ring.


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°)


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).


Lines of Longitude


Lines of Latitude


Combined!


The units that we will be using to measure are:Degrees (°)

North 39° Minutes ( ‘ )06And . . .

THOUSANDTHS of Minutes!

.582’

West 77° 06 .086’


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.


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.


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.


Using GPS Technology to Locate Trees


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


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. . .


A Map!

Use the map to look for landmarks, to stay on trails, to gauge distances, and to find your way back!


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

GOTO, 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.


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.


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.


THINGS TO KEEP IN MIND:

Do not cross roads. 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.


IMPORTANT POINTS:

GPS technology is limited – tree canopy and cloud cover affect signal strength

Be aware of your direction of travel. Use a map.

Watch the time! Return on time!

Documents

Cheap GPS (From xkcd)