GEOG 121 Project 2b:
Integrating GPS and GIS


Janet Beekman

Global Positionaling System(GPS) is a system consisting of a minumun of 24 satellites, control stations, and users. The GPS system uses the same principle as trilateration, which is based on distances, but extended to three dimensions to do gelocation or to determine positions on the earth. The GPS receiver must be in view of at least 3 satellites to get x,y data and in view of 4 or more to get x,y, z, and velocity data. The map above is of the Penn State University Park campus and the waypoints of the worksheet we were given. Click here to see our scanned worksheet. The other members of my group were Jonathan Walker and Andrea Smyers The points we found were the sundial in front of Old Main, the center of the courtyard between Old Botany building and Chambers building, the intersection of Pollack Road and the access road to behind Willard building, the cement vase in the West Halls Quad, the pull off area in front of the Pattee library entrance, the front of the Business Administration building, and one we added as reference, the obelisk. While we describe our points to a specific location, the 10 meter accuracy of our GPS receiver makes it more in that area plus or minus up to 10 meters. Some of the points when we plotted them on the map seem right on were we thought. However others such as the point we describe as the sundial in front of Old Main appears on the map to be in the lawn in front of the sundial.

In addition to plotting the waypoints from our worksheet. I on my way to class collected several additional points along Pollack Road. I started right before Willard building, then did in front of both entrances to Willard, in front of Steidle, in front of Hosler, then on to IST, and ending in front of Walker. These points are shown in the map below. I wanted to do this because I wanted to try using the GPS receiver to collect data points and then input them into my map. This is what we do at work. If for example there is a new area of trees, we will go out with our GPS device and collect points for each tree, input them, and add them to our map. I had not had an opportunity to do this data collection myself. This assignment was helpful because now I know how and have done it.

The Software I used to do this assignment is the Waypoint+ software in the 208 Walker lab. This software read points from the GPS unit and converted them to a text file on the disk. I had to specify the coordinates to Decimal Degrees and the Units to Statute Miles. I next had to set the Datum to WGS84 which is the one used by the satellites. I edited the text file using Microsoft Excel to delete extra points that were in the memory of the GPS unit before I collected my points and extra columns which are not needed. The resultant file is just three columns, waypoint number, latitude, and longitude in decimal degrees. I then used ESRI ArcMap(ArcView) 9.0 to add the points from the trimmed excel file to my campus map. ArcMap not only input the points but it also converted the coordinates from geographics coordinates to those of the rest of the map which are state planer, 1983, PA north(feet) coordinates. I also used the scanning software in the Pollack computer lab and Microsoft Picture Manager to reduce my images to ones more appropriate for the web. The rest of the equipment used was the Garmin GPS 12 receiver, and the cabel to connect it to the computer. I was part of the Project Leadership Team for this project. Click here to see our Project Leadership presentation.


Sources
DiBiase, David (2002) Understanding Geographic Data. Module 2: Land Survey and GPS. ESRI Virtual Campus http://campus.esri.com Accessed 29 October 2004.
GPS 12 Personal Navigator Owners Manual and Reference(1999). Garmin Corporation http://www.garmin.com/ Accessed 29 October 2004.
Online Lecture Materials for Geog 121, Lecture 5 on Angel, Accessed 10 October 2004.