What combination of geospatial tools did the class to use in order to conduct the survey? Why?
- The class at first started out using a survey grade GPS unit to geocode the exact locations of each headstone, create an attribute table to record all legible information of the tombstones and finally to take pictures of each headstones. Others tools that were used included the Inspire, Rededge, and Phantom UAV drones. These UAV drone were able to take areal photos of the cemetery to be used as a base map. Lastly each group of students had a pen and note book that they used to create hard copies of all of the information on the headstones.
What is the accuracy of the equipment you are intending to use?
- The UAV drones are accurate down to the centimeter as well as the Survey Grade GPS unit. The accuracy of the hard copy of the data depends solely on the legibility of each tombstone.
How was data recorded? List the different methods and state why a pure digital approach is not always best. What media types are being used for data collection? Formats?
- The Inspire drone used a camera to take pictures of the cemetery that would later be compiled into one image by use of the software Pix4DMapper. The Survey Grade GPS unit has the ability to compile a list of attributes for each point that was taken. The attributes included were name of the deceased, year born, year of death, and the legibility of the tombstone. This data would later be transformed over to ESRI's ArcMaps where it could be overlaid on the Inspire UAV imagery.
This method of data retrieval at times can be the best and quickest way to gather the data that was missing, however there is one very large drawback to this method, signal interference. The class ran into this problem after an hour of data collection. In the southwest corner of the cemetery there are a few very large trees that are located directly over a a handful of tombstones. This prohibited the Survey Grade GPS from getting a strong enough signal to record the locations of those particular tombstones. This foliage also created problems for the UAV drone. When the data from the drone was being compiled into one image the program was unable to create a proper image of the data. The foliage in that southwest corner created large shadows, due to the collection occurring at 4:00PM in the afternoon, which put the sun directly behind these trees. These shadows lead to the software program being unable to compile the data correctly. The imagery from the Inspire was very distorted in the that same corner.
Another issue that occurred in regards to the GPS unit was the time it took for each tombstone to be properly collect and have all of the attributes added. Each tombstone took three to four minutes to collect all of the data. Also before each group could get started the previous group had to show go through all of the steps to properly operate the GPS unit.
What equipment failures occurred if any? What was done to remedy the situation?
- The equipment failure was covered in the previous paragraph. The steps the class took to remedy the stated problems was to first create a hard copy diagram of the cemetery and give it a standard coding system that the class would use. The system was simple, the row furthest to the west was row one, the row second closest to the west was row to and so forth. To find the exact location of a particular tombstone in each row a letter system was added to each row. So the tombstone in the southern most point in each row was labeled as "A" and the further north down the row a tombstone was the further down the alphabet it was labeled. So Row 1 tombstone 5 was labeled as "1E". The class used this method to label all of the tombstones in the cemetery along with the attributes of each tombstone. With these location of each tombstone the class will be able to digitize the each of the tombstones and add the attribute data to each location.
The UAV issue was solved by going to the cemetery a second time on an overcast day at 12:00PM, to try and avoid the interference of shadows. Two different UAVs were flown, the Rededge and the Phantom drones. The data was collected and entered into Pix4DMapper where it was compiled correctly. Figure 1.1 shows the image from the Phantom Drone.
Figure 1.1: Phantom UAV Imagery
What might have been done to facilitate data collection in terms of equipment and refining the method?
- The best way to improve data collection for this problem would be to get another Survey Grade GPS unit and teach the groups how to operate before getting into the field to help streamline the process. Also collecting the data at low shadow points of the day would be very effective for improving data collection quality.
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