On September 30th, 2017, the Geography 336 class ventured to Litchfield Mine in Eau Claire, WI. This field outing was a rare opportunity for students to utilize and evaluate a spectrum of highly sophisticated field equipment. This activity required students to place Ground Control Points (GCPs) and use a variety of GPS units to gather coordinate data at each GCP. The GPS units ranged from highly accurate to significantly less precise to display the variety of GPS markers available in today's market. Unmanned Aircraft Systems (UAS) platforms were also utilized to gather aerial imagery over the study area. The focus of this lab was to simply collect the data and become familiarized with the different types of surveying platforms. The data results will be presented in the next lab. Figure 1 below displays a segment of the study site.
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| Figure 1 - Litchfield Mine Site |
Study Area
The mine was located off of highway 37 south, the coordinates being 44.7741731, -91.5713886. The Litchfield mine is regarded as an aggregate mine, consisting of coarse particulate material such as crushed stone, clay, sand and gravel. Such materials can be used to establish concrete for the construction of roads, buildings and dams. Figure 2 displays a satellite image of the study area.
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| Figure 2 - Aerial satellite image of Litchfield Mine (courtesy google maps) |
Methods
The activities of this lab involved collecting GCPs throughout the study area, as well as obtaining aerial imagery and topographic data. Sixteen unique GCPs were distributed within the survey area in order to geo-reference the data captured by the UAS platforms. All the data collected for this blog will be processed on a later date over ArcGIS. Students were first instructed to establish 16 GCPs throughout the study area. Figure 3 shows an example of a GCP marker.
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| Figure 3 - GCP Marker |
It was important that students did not cluster the GCPs, and areas with more terrain required a heavier concentration of points. Once all 16 were established, the class broke off into separate groups in order to record the latitude and longitude of each point. To illustrate the variability in precision, multiple GPS units were used. Coordinates were recorded on Cellular devices, a Bad Elf GPS unit and a TopCon HiPer HR and SR. Figure 4 below shows students positioning the Topcon HiPer on one of the GCPs.
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| Figure 4 - Students and professor establishing Topcon HiPer on a GCP |
It was essential that the pole was perfectly straight up and down to record an accurate reading. When recording data with this particular GPS, one must wait until reads "fixed", then it will initiate collection. Once it has collected thirty coordinates, selecting "Store" and "Save" will give one accuracy within a few millimeters accuracy. Other coordinates were collected with Arrow GPS markers from Menet Aero. These markers were solar powered GCPs, positioning with satellites and ranging in accuracy from 2 to 6 cm.
After collecting GCP coordinates, the class was introduced to a variety of highly sophisticated UAS platforms from Menet Aero and TopCon Solutions. Four different drones were utilized to record the spatial location of the GCPs via aerial imagery. These models included the DJI Phantom 3 Pro, Sensefly eBee, C-Astral Bramor ppX and the M600 Pro.
DJI Phantom 3 Pro
This was a small rotary wing UAS from Menet Aero. On a full charge, the unit could fly for one hour. It had a camera fixed on the bottom and ran on software called MOCO (minimum obstacle collision avoidance). An app called "Drone Deploy" was used to operate the flight, enabling the user to control and direct the flight to collect coordinate data of GCPs as well as gather aerial imagery of the study site. Figure 5 shows the Phantom.
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| Figure 5 - Phantom 3 Pro Unit |
Sensefly Ebee
This particular aircraft (from Topcon Solution) was a fixed wing unit, composed of light weight Styrofoam. The Ebee is able to handle wind speeds up to 28 mph, being programmed to return to the launch site under the circumstances of high wind speed, poor GPS signal or poor connection to the controller. The Ebee was held in the air and then released once it starts up. It captured images from 160 feet in the air, having a 40 mp camera. In mid-flight, the aircraft began to spiral out of control, eventually crashing into the Chippewa River, where it was later recovered. Normal landing procedure for this UAS would involve using a landing strip. A disadvantage of this aircraft, then, is the fact that it needs a lot of space for landing. Figure 6 below displays the Sensefly Ebee.
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| Figure 6 - Sensefly Ebee pre take-off |
M600 Pro
The next aircraft flown was a larger, 6-rotor drone from Menet Aero. It is capable of flights up to 40 minutes. This particular drone used Real Time Kinematic (RTK) satellite, which uses coordinate data to navigate in flight. It took off and landed smoothly. Figure 7 displays the unit.
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| Figure 7 - M600 Pro awaiting take-off |
C-Astral Bramor w/ Sony a6000
The last aircraft demonstrated to the class was the C-Astral Bramor w/ Sony a6000 from Menet Aero, shown in figure 8 below. This was another fixed-wing drone, but with a much larger wing span than the Sensefly Ebee. A sling-shot-like structure was used to launch the unit into the air. Landing involves deploying a parachute to enable it to land carefully back to the launch site. Unfortunately for this demo, the parachute failed to deploy, and the drone ended up crashing.
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| Figure 8 - Launch pad of Menet Aero's fixed wing |
Conclusions
Although the coordinate readings are different for the cell phone and Bad Elf degree points, it is impossible to determine which one was more precise until the data has been processed. Figures 9 and 10 below show the coordinate readings for both devices. It also appeared that Rotary-winged aircrafts proved their reliability over fixed-winged aircrafts on this outing, as they smoothly took off and landed, unlike the fix wings- which never successfully made it back to land. Soon this coordinate data will be unified with the aerial images captured by the drones to create a map of the mine.
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| Figure 9 - Coordinate Readings from Bad Elf |
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| Figure 10 - Coordinate Readings from Phones (Z=Elevation) |
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