Forensic Science Geocaching Activity

Developed by Tracy Trimpe for the 2009 Smithsonian Summer Camp http://sciencespot.net/

What is GPS?

• GPS stands for Global Positioning System.

• It uses 24 satellites positioned around the globe. The satellites are 12,000 miles from Earth’s surface.

• We use GPS receivers to connect with the satellites to learn our position on Earth’s surface, which are based on latitude and longitude.

Havana Junior High Latitude = 40.296917 N Longitude = 90.050007 W How Stuff Works: GPS Explained

Images: http://geomag.usgs.gov/images/gps_001.jpg and http://www.portcities.org.uk/london/upload/img_400/longitude_latitude.gif

How accurate is a GPS receiver?

With today’s GPS receivers we can get as close as 3 meters or 9 feet.

To determine our position, the receiver measures the time it takes to receive a signal from a satellite and converts it to a distance.

Satellite 1 We need a total of 3 satellites to get an accurate reading.

Satellite 2 Satellite 3

How is GPS used in investigations?

• Provide coordinates (locations) for emergency responders • Document the layout of a crime scene or accident site • Document the locations of specific pieces of evidence, vehicles, etc.

• Determine distance between locations (i.e. primary/secondary crime scene) • Track victims or suspects to identify their location or determine where they have traveled

FROM THE NEWS …

In one case in California, a suspect of several convenience store holdups was being monitored with a vehicle tracking device. When he held up another convenience store, the tracker proved that he had parked two blocks away from the store around the time of the holdup and left a few minutes after. This information from the tracker was used along with DNA evidence and a search warrant to make an arrest.

One of the many kinds of GPS systems also helped in the convicting of a man in New York, changing the charge from reckless endangerment to murder. This information was used to prove that George Ford purposefully murdered the babysitter that he had hired instead of accidently as he claimed. This tracking device, which had been planted by the man’s suspicious wife, provided information that contradicted what the man claimed had happened.

Source: http://www.rmtracking.com/blog/gps-tracking/gps-systems-work-to-fight-crime/

What is geocaching?

Geocaching

- An outdoor treasure-hunting game in which the participants use a GPS receiver to hide and seek containers called "geocaches“ (Wikipedia, 2009)

Cache

- A typical cache is a small waterproof container (usually a tupperware or ammo box) containing a logbook and "treasure," usually toys or trinkets of little value.

Microcache

– A small container (i.e. film canister) containing only a logbook.

Waypoints

– Locations where a cache is hidden; identified by latitude and longitude.

Travel Bugs & Geocoins

– Items that geocachers place in caches and track their locations as other geocaches move them to another cache.

Muggles

– Refers to people who do not geocache.

Geocaching.com

– Website devoted to geocaching and provides information on all the caches around the world.

Cafepress.com Shirt

As of July 2, 2009, there were 839,756 geocaches around the world!

GPS Receivers

Each GPS receiver has many buttons with different functions.

Find Button

– Use to find a waypoint.

Thumbstick

– A “joystick” that moves up, down, left, and right to help you select options. Push it in to choose an option.

Antenna

– Keep the unit flat in your hand so that the antenna is pointed up at the sky.

Page Button

– Press this button to change screens

Power Button

– Use this button to turn the unit on and off