23 Collect data using GPS
A quick review of collecting data using a GPS device:
- Static data: Collect the latitude and longitude of three geodetic benchmarks near the Student building
- Dynamic data: Measure two IU buildings while the GPS antenna is in motion, i.e., walking around the building with a GPS device on
Scavenger Hunt (1): Find benchmarks using GPS
Through the mapping exercise of “XY Coordinate,” we have figured out the preliminary locations of the three geodetic benchmarks. We will hunt for this treasure (!) using a hand-held GPS device.
- To mark the above latitude and longitudes on your GPS, enter the coordinate values in the “Where to? >Coordinates” dialog in the GPS device.
- Type the first benchmark coordinate.
- You are ready to find the first benchmark – walk to find it
- Take the coordinates three times for each benchmark. Some tips are
- Click on the signal strength icon to see the satellites, the latitude/longitude of your current location, and the accuracy each time you record the coordinates.
- Wait a few minutes between each collection. You will find that the satellites are constantly moving, appearing, and disappearing. The accuracy level of the GPS also dynamically changes depending on the availability of satellites.
Table (3 pts.): Fill in the table below with three points you captured at each benchmark (Note: The sheet that contains the table below will be provided before the field work.)
Type your exercise (Figure)
Scavenger Hunt (2): Measure building area using GPS
We can also measure the area of an object using GPS.
- Choose the two buildings near your last benchmark location.
- Using the “calculate area” tool on the GPS device, measure the area of two campus buildings.
Final Lab Deliverable
Figure (2 pts.): Use your table to make a map with your three generated locations for each benchmark (so, the total of nine points). Overlay the nine new locations with the three original benchmark locations you have already created before the fieldwork. Display both the original and your locations overlaid with the aerial photo. Please double-check that your map includes all key map elements.
Question 1 (2 pts.): Based on the Geodetic Benchmarks collection,
- Do your three-time GPS collections show the exact coordinates each time you record the survey markers?
- If your answer is Yes, discuss the significant parameters that make each record different. If your answer is no, also discuss what could potentially induce the duplicate coordinate records.
Question 2 (2 pts.): Compare and contrast the measured area to the polygons of the IU buildings layer in the Lab 7 data folder. Look at the IU building layer’s attribute table to find the building area; the area is square feet. Describe how much difference you found between your measurement and building polygon layers, and discuss what could be the potential error source that caused the error.