Field GISSummer, 2009 Assignment 3GPS ProjectReadings:Trimble GeoExplorer 3 Tutorial File (600+ pages!!! mostly fluff, but it has full instructions for all handheld ops)Mapping Systems General Reference (114 pgs, and well worth reading!!!)Trimble Online Tutorial (with animations!)Things to include in the writeup are mostly in ITALIC... Try to keep it under 10 pages... Part 1. It's useful to compare the results of GPS readings to known benchmarks. Use the distance formula to calculate the distance between the points you wrote down and the known benchmark location. Use the same formula to calculate the distance between the end-points of the 10m tape. Do NOT use the GIS software to calculate this. Part 2. Collect data with garmins and trimbles at the Duniway track and the upper park area. Note which track number you are on (8 tracks?). Plot differentially corrected data, non-corrected data and garmin data to see how they are related. Work in groups of 2 to 3. Use data collected by other groups to fill in the database of observations. How would you collect the data differently next time? How would planning software help? Transfer the data to PC format in the Geology computer lab or CH1, differentially correct as appropriate, and bring the data into ArcMap. Print a map clearly showing the different data sets, use multiple maps if necessary. Refer to each figure in your report and include the figure near where it is mentioned. No dumping a bunch of figures in an appendix! For differential correction: Use the USFS/BLM site and download the individual base files to your working directory. You will also determine your pace using a tape measure, include this result in your report. Also discuss line width relationship to scale of map. Measure the length of one of the tracks or other objects using your pace and compare it to data collected with a GPS. Remember to ALWAYS do reality checks like this. Include this comparison, and show your calculations. Discuss sources of error in using GPS in your report. Discuss applications for which you would use different collection methods with different instruments (Garmin vs Trimble). Part 3 Use the planning software to determine the best time to avoid obstacles at Duniway. Create a data dictionary for collecting points, lines and polygons at this site, download the data dictionary to a Trimble and go collect the data! Plot this data on your basemaps from assignment 2. Which basemaps work best? Why?
Answer these questions from the readings: 1. How many satellites does it take to get a 3D fix? Why? 2. What kind of errors can be corrected by differential processing? 3. What is the relationship between Satellite geometry and PDOP? 4. What is the difference between "reality", the "Data Model of Reality" and a "Computer Oriented Data Model" (Rasmussen). 5. How would you collect a GPS reading for a feature that cannot be reached, or has poor GPS coverage? Please give a specific example from this assignment.
Questions? Comments? Contact Percyd@pdx.edu
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