GPS Basics

2007 NCSTA Institute

Interesting revelations en route to teaching the use of GPS receivers

to middle schoolers:

1. Most students (and a good number of adults) do not have a good grasp of the concepts of latitude and longitude.

2. Following a GPS without at least some map-reading ability can be trouble.

3. Many folks have an interesting concept of how GPS units work.

Three Questions to Build From…

• Where were you born?

• Where was your most favorite vacation?

• Where is the furthest away from home you

have ever been?

Why Latitude & Longitude?(Location. Location. Location.)

• If we wanted to meet in Barcelona for a cold beverage, how best could we pinpoint a

location? How about in NYC? Kansas?

• If we wanted to plot attributes (rainfall amounts, elevation, land use) onto a GIS map, how best

could we pinpoint each location?

Latitude & Longitude create a grid system which gives every physical location its own specific name

or marker.

Latitude & Longitude create a grid system which gives every physical location its own specific name

or marker.

As Long As You Include the Direction!!

The Dilemma with Degrees

36 Degrees North, 80 Degrees West

“Hey! Where are you!”

“I’m in Virginia. Where are you?”

“High Point.”

“Oh…”

*With Degrees only, we can be precise to 69 miles.

The Solution

• Degrees, Minutes, Seconds36° 23’ 19”

OR

• Degrees, Minutes, Decimals36° 23.317’

*With 1000ths of Minute, we can be precise to a matter of meters.

How does this “System” work?

With solid signal from one satellite, the receiver knows it is a given distance from the satellite, but it does not know what direction….

With solid signal from two satellites, the receiver knows it can only be at those locations that meet both distance criteria... (intersections of circles)

So with solid signal from three satellites, our receiver can pinpoint its location and give us an accurate latitude & longitude….

…. Right????

Darn Topography

Contact Info

• Feel Free to Contact Me with any Questions

Kevin MooreBetsy-Jeff Penn 4H Education Center

336-349-9445kevin_moore@ncsu.edu

www.bjpenn4h.org