Introduction
GeoSTACField Exercise
. . .by Jacob Mundt
This portion of this course will apply the theoretical and practical aspects of GPS you learned in the previous two exercises. Using your map, select an area of interest to you with features you can access(roads, trails, rivers, etc.). You will travel to this area and take a series of points which you can locate on your map, and you will record the coordinates at each point. The number and placement of these points is left flexible, however a quality project should plan on spending at least four hours in the field collecting data.
After this is complete, you will mark on your map your GPS coordinates using a metric scale or the UTM grids previously provided. It is important at this stage to use the map coordinates, not simply to mark the point where you should be located.
After all GPS locations have been marked on the map, an analysis should be done on the accuracy of the overlay. Do the points lay where they should? Is there a consistant bias? What is the error on each point? Is this error within the expected range from what you have previously learned? Finally, compare the sources of error, GPS vs. map.
EXAMPLE: ROAD INTERSECTIONS IN POCATELLO, IDAHO
Project Objective: Map GPS points at projected centerlines of road intersections.
Project Methods: Using a handheld GPS unit, the average of 30 GPS locations will be recorded at each road intersection. 30 points will ensure a reasonable estimate of the true location. Projected centerline intersections are typically visually discernable to within a decimeter in the field, supplying very high control on the actual geographic location of each GPS point. After collection, these points will be plotted on a base map of the area. The following is a graphic of what your project might look like at this stage:
In the map above, the GPS locations (green colored dots) are displayed at a large scale so that they are visible, however if one were to look at them up close it would be observable that they do not exactly overlay the street intersections. How do your points align according to both the GPS and map coordinates, and how does this compare to your actual location?
When you have collected, plotted, and evaluated your data, make a DETAILED write up of your objective, methods, and results, including answers to the questions above. This write-up should be included in your final report. If you choose to do your project using GIS (optional) you should also include a jpg of your map in your write-up.