What is GPS?
How Does It Work?
Who Uses It?
Can GPS Help Me?
Where Do I Start?
Feedback

What is GPS?

The Global Positioning System (GPS) is a satellite navigation system developed and maintained by the U.S. Department of Defense (DOD). Based on a constellation of 24 satellites in very high orbit, the system avoids problems encountered by land-based systems and provides accurate positions anywhere in the world, 24 hours a day. GPS receivers are becoming small enough and cheap enough to be used cost-effectively in a wide variety of applications, ranging from electronic navigation for cars to landing aircraft in zero-visibilty conditions. In geography, perhaps the greatest potential of GPS is as a tool for capturing both positional and attribute data for use in geographic information systems (GIS).

How does it work?

Radio signals are sent from orbiting satellites to earth. GPS receivers on the ground collect the radio signals from several statellites and use them to calculate the distance between the receiver and each satellite. These distances are then used to calculate the position of the receiver (a procedure known as triangulation). GPS receivers have the ability to store attribute information in addition to position information. For example, not only can the GPS receiver store the position of a light pole, but it can also store attributes of the light pole, such as height, number of lights, condition, date visited and so on.

Who uses it?

GPS is widely used in a variety of applications in fields ranging from environmental studies to urban planning. In geography, GPS is particularly effective as a tool for obtaining field data for use in a GIS. Examples of recent GPS projects in geography and environmental science at UNT include:

• Mapping shorelines to monitor coastal erosion
• Mapping pollution point sources
• Mapping sample locations in tidal marshes and lakes
• Mapping well locations for groundwater monitoring
• Mapping a landfill boundary
• Mapping parking lot boundaries
• Mapping vegetation
• Mapping street addresses for locating 911 calls
  

The following is a sample of GPS users in the public and private sectors:

• Public Works
• Planning Departments
• Tax Departments
• Parks and Recreation
• Police and Fire Service
• Environmental agencies
• Surveying companies
• Agriculture
• Forestry
• Mining
• and many more....
  

Can GPS help me?

If your project requires accurate and efficient collection of position and attribute data in the field, then GPS is for you. Once collected, this position and attribute data can be readily transferred to GIS environments to store, update, manipulate, analyze, and display all forms of geographically referenced information.

Examples of geographic features that can be captured by GPS:
Point Features
Signs
Manhole covers
Fire hydrants
Light poles
Recycling sites
Bird nests
Railway crossings
Bus stops
Trees
Crime scenes
Pipe breaks
Accident locations
Gas stations
Payphones
Pot holes
Animal burrows
Storm drains
Line Features
Streets
Sidewalks
Fitness trails
Sewer lines
Water lines
Driveways
Geologic boundaries
Bus routes
Fence lines
Animal trails
Power lines
Fault lines
Pipe lines
Streams
Shore lines
Area Features
Parks
Wetlands
Landfills
Planning zones
Oil spills
Subdivisions
Vegetation communities
Wildlife habitats
Parking lots
Rock outcrops
Ponds
Construction sites

Where Do I Start?

In a typical GPS project, the steps you should follow are:

• Create a project
• Create a data dictionary
• Mission planning
• Field mapping
• Downloading files to a PC
• Differential correction
• Displaying positions and attributes
• Exporting data to a GIS

All these steps are described on the linked web pages.

Feedback

If you have questions or comments, please email Harry Williams. Questions and answers will be used to develop a FAQ page.