1. Creating Waypoints and Determining Accuracy Using GPS Testing Accuracy of the GPS Using Waypoints Using a Garmin GPS, we chose three objects to use as reference points on the University of Michigan-Dearborn campus: a fire hydrant, a manhole, and a lamp post. Standing on or in very close proximity to these locations, we generated waypoints, where the GPS device stored data of our exact location in latitude and longitude accurate to three figures in seconds. We then returned to these locations approximately ten minutes later, and regenerated new waypoints to compare differences in accuracy. We later calculated the average distance between the actual location of the selected points and the averaged first set and last set of waypoints taken at these locations by making measurements between the georeferenced waypoints which were imported onto google earth. This distance is called the residual offset. Ideally, one would create a minimum of three sets to provide a good statistical control. Depending on what surrounds the GPS device, waypoint readings may be drastically different. Many of our initial waypoints that were near or between large buildings were depicted by the GPS as being anywhere from 21to 40 feet away from their actual location. Introduction Global Positioning Systems (GPS) involves three parties: a space segment, control segment, and users. Satellites broadcast radio transmissions which are monitored by ground monitoring stations worldwide. A GPS user has a receiver device, which detects the transmitted signals from several (optimally, four or more satellites) to determine the exact geospatial location, as well as elevation of the user. In our case, the GPS device used also had the ability to record and store detailed location information as a waypoint in real time as the user found necessary. Stephanie Vollick, Ian Tran 04-11-08 Fire Hydrant Lamp Post Manhole Accuracy Test Points at the University of Michigan-Dearborn Calculation of Waypoint Residual Error Average Residual Manhole: 21.54 feet Lamp Post: 6.67 feet Fire Hydrant: 5.37 feet Average Residual: 11.19 feet Generating a Series of Waypoints to determine Stop Sign Distribution on Campus We generated 14 waypoints, each at a location where stop signs were found at. At intersections, we chose exclude any additional stop signs that were in close proximity to our initially chosen stop sign. We found that the stop signs were roughly distributed about one hundred feet apart from each other on the Western side of campus, while the distance between stop signs on the East side of campus were substantially larger. Conclusion GPS accuracy varies with any obstacles which may block transmissions from satellites, if the user is in motion, and the location or transmission strength of the satellites used for providing coordinate information. As such, it is best to ensure that there is a way to establish an acceptable margin of error by using test waypoint locations, and also double check distances or locations with additional methods, be it through in-field measuring, or via Geographic Information Systems such as Google Earth.