UAS Flight

Introduction

This lab is focused on data collection using an unmanned aerial system. Unfortunately, we weren't actually able to individually set up a flight path and collect any data in this exercise, which makes writing about it difficult. Originally I was hoping to actually capture some NIR reflectance values for the Priory, however due to unfavorable weather conditions this was not possible. Therefore, this post will be focused on the steps necessary to set a project up using

Methods

When starting up the project it is important to note environmental conditions, such as temperature, cloud cover, and wind speed/direction. Today it was in the low 50s with 100 percent stratus cloud cover and winds at 4 miles per hour with gusts much higher. If environmental conditions are unfavorable it is important to postpone the project. Before begenning the pre-flight check it is important to get the project set up on the Mission Planner software. This program allows extensive customization, such as camera width, flying height, time in between image captures, and flight speed. It is important to select the best settings for the job at hand. If you are collecting data for precision agriculture you should select camera lens with a very narrow view to eliminate off-nadir image capture. If you are collecting data for a grassy field, one would be able to use a much wider camera lense and in turn take fewer flight lines to obtain the necessary data (Figure 1).

Figure 1  Mission Planner user interface. As you can see, a rectangular box is drawn on the screen. The software will then create flight paths that will ensure the entire study area is covered. Flight lines are based on camera width and flying height.

Next, we draw the desire flight path in the Mission Planner software. By drawing a rectangular box over the study area, Mission Planner takes into account the width of camera lens and other variables selected above, and creates an appropraite flight path. After the flight path has been determined we are able to start the pre-flight check.
The pre-flight check is the most important aspect of any UAS mission. If not taken seriously a malfunction in any part of the system can lead to costly damage to the UAS and time spent repairing it. The pre-flight check involves checking various boxes in the Mission Planner program. Included in the pre-flight check are tests for electrical connections, frame connections, motor connections, secure props, secure battery, and secure antenna. After the checklist has been completed the UAS is powered up (Figure 2).

Figure 2  UAV that was used to colect data in the visible spectrum.

The UAS is manually lifted off the ground. Once it gets to a safe height above the ground the operator can swith into autopilot mode. When switched into autopilot the Mission Planner software takes over and flights the predetermined flight lines. If there is a malfunction anywhere in the UAS, the operator has the power to switch back to control and land the UAV safely. After the flight has been completed, the UAV automatically lands. Upon landing the post-flight check is to be completed. The post flight check involves noting the flight time, whether any problems occurred, making sure the data was properly collected, and safely shutting down the UAV.

Results

Due to heavy winds the UAS quickly traveled off the desired path. This led to the mission being aborted shortly after takeoff.Therefore, there was very little data collected. Pictured below are a few aerials that were collected in the NIR spectrum. NIR is highly refelected by healthy vegetation due the the cell structure of the plant. Therefore, areas that appear white in an NIR image and dense, heathly vegetation while areas that appear gray and black are less healthy. NIR images are commonly given a false color. In a false color NIR image the NIR band is assigned the color red, the red portion of the image is assigned the green portion of the spectrum, and the green coloring in the image is assigned the blue portion of the spectrum. This basically turns the image a pinkish color where healthy vegetation occurs. Figure X below is the original image collected from the UAS. Unfortunately, I was unable to create a false color infrared image due to the images being a .jpg file format. Also, due to time and weather constraints, we were unable to process the data any further. If given the opportunity we would have been able to combine all the images collected into 1 much larger image similar to what is seen by landsat data (Figure 3).

Figure 3  NIR image collected by the UAV. This image shows areas of healthy vegetation as white while areas with little or no vegetation appear black. The area in the upper right of the image is the parking lot of the Priory and the area in the right of the image is a deciduous tree.

If we were to process the images further, we would be able to create a string of images that overlap each other sufficiently. We would then be able to mosiac the images together, using a histogram matching technique to create seamless images that could be used for analysis. A process like this is very common in precision agriculture practices.

Conclusion

As previously state, there was no data that was collected except a few aerial images. Therefore, we were unable to do any NDVI calculations to determine where vegetation was the most healthy, or anything of the sort. Overall, based on some of the horror stories associated with UAV crashes this mission was not a total failure in that both UAVs returned to the lab in 1 piece.

Navigation with a GPS

 

 

Introduction

    As a continuation from last weeks exercise, this weeks exercise was to create a GPS navigation course that will be used by the next field methods class. In order to accomplish this task we are to plot points on the navigation map created in exercise 3, navigate to them using techniques learned in last weeks exercise, and enter the points into a Trimble Juno GPS device. Our goal was to make a course that will be difficult for next years class. In order to do this we navigated around the building on the Priory a few times. This makes keeping track of the pace count very inaccurate. However, if they use a map with a decent aerial image they should have no problem locating where to enter the woods to find each of the points.

Study Area

This Priory is located three miles south of the UW- Eau Claire campus. It is 112 acres of multipurpose land that is used as a dormitory for UW- Eau Claire students and a day care for the children of university employees. It contains areas of dense underbrush, steep valleys, and a section with rows of evergreen trees. There is also a few small ponds located in the northeastern corner of the grounds, near Highway 94.

Figure 1  The Priory is located 3 miles south of the UW- Eau Claire campus.

 

 

Methods

Originally, we plotted five points throughout the navigation boundary that we were to navigate to using the skills learned during the previous exercise. After locating our first point, we decided to move the location slightly to the north to make it more difficult for the next class. After finding a suitable location we collected a point using the Trimble Juno GPS unit. After the point was collected, we navigated to the next point. After finding a suitable location for the tree marker we collected another point. This process continued for all five locational points throughout the study area. As you can see below, the location of the actual GPS points is slightly different from original points we were going to collect (Figure 2). After returning to the Cartography lab, we imported the feature class of collected points back into the geodatabase.

Figure 2  The original location of the GPS points versus the actual location of collect points. Some points were moved slightly to make a more difficult course for next years class.

Figure 3  The first of the points marked for next years class. The four other trees will have similar markings to this.  

Results

The following table contains the points and the x,y coordinates in meters based on UTM Zone 15 N coordinate system (Figure 4). Each of the points was mapped in ArcMap and given an appropraite label (Figure 5). Due to time concerns we did not collect the points in the correct order that next years students will have to. We simply located the closest point and set the GPS point.

Figure 4  Table showing the point name, id, and the xy coordinates based on the UTM Zone 15 projection.

 

Figure 5  The location of the points collected overlaid on an aerial.

Conclusion

The location of the points was spread out over a very large area. This will make it difficult for next years students to find the locations accurately. One thing that benefits the students is that there is very little elevation change in this area compared to other areas of the Priory. This should make the process go a lot faster since they will not be required to climb up and down 50 degree slopes to get to their points.





 

Field Navigation part 1

 

Introduction

     This weeks exercise is aimed at navigating to five predetermined points around the Priory using a navigation map that was created in exercise three and a compass. This archaic technique is very useful when navigating in areas where GPS signal is weak or nonexistent, such as forests with dense crown cover.

Study Area

      Formerly St. Bede's Monetary, the Priory was purchased by the UW-Eau Claire Foundation in 2011 and is currently being leased to the University of Wisconsin- Eau Claire for expanded educational purposes. It is located about three miles South of the City of Eau Claire, WI (Figure 1). It is currently being used as a day care center for professors with young children. It is also used as dormitories for UW- Eau Claire students. The Priory consists of 3 buildings totaling around 80,000 square feet of space on a 112 acre forested lot. The land is heavily wooded and contains a combination of flat terrain along with very steep ridges with slopes up to 63 degrees (Figure 2).

Figure 1  Locational map of the Priory. The Priory is located three miles South of Eau Claire in Eau Claire County, WI.

 

Figure 2  Original navigation map that was used in this exercise. It contains 5 foot contour intervals, an elevation model that was set to 50% transparent, and an underlying aerial image.

In many areas magnetic declination would need to be considered. However, in the study area the magnetic declination is only about negative 1.4 degrees. Areas on the East coast have magnetic declinations up to 20 degrees. This could cause a huge problem when in the field if not taken into account.

Methods 

      The methods associated with this exercise were quite simple. To start we plotted the points, in order, on the navigation map based on the UTM coordinates that where provided by the professor. We then connected the lines in order that were to be collected (Figure 3). We measured the distance on the map and converted it to real life distance using the scale bar. We then converted that into the number of paces it would take to get to each point. We then set the compass on the map, set the orienteering arrow to geographic north on the map, aligned the magnetic needle within the orienteering needle, and followed the direction of travel arrow. After arriving at the first of the points we did the same process. Set the compass on the straight line to the next point, set the orienteering arrow to geographic North, aligned the magnetic arrow inside the orienteering arrow, and followed the direction of travel arrow. An example of the process is shown in Figure 4.

 

Figure 3 Navigation map showing our plotted points and the straight line from 1 point to the next.

 

Figure 4  Cartoon showing the basic process of setting up the compass. Here, they line of the compass along the start/destination line, set the compass dial to true north on the map, align the true north arrow and the magnetic arrow, and follow the direction of travel arrow while counting paces.

 

Results

Seen below are two of the photos that were taken at the predetermined locations. They were marked by bright pink tape wrapped around birch trees (Figure 3,4) These photos were taken to provide evidence that the points were actually located. We were able to locate all five points in order with relative ease. The most difficult aspect of this exercise was scaling the valleys that were present in the Priory.

Figure 5  One of the navigation points as marked by the bright pink tape.

Figure 6  Another of the navigation points.



Conclusion

As previously stated, this lab was fairly easy. We were able to located all five points in under an hour and a half. Keeping the pace count correct was sometimes difficult because we had to navigate around dense brush and very steep slopes. Therefore, the pace count was used as more of an estimate as to where we were located instead of an actual measurement unit. There were a few cases where our pace count was off by 20 or 30 paces. This is not a problem when searching for bright pink tags located on birch trees, however this could have been a problem if navigating to something less noticeable. In addition, being in such a small geographic area made the relativity of the pace count less of a problem. If we were navigating in a national forest that spans several hundreds of miles our location would have been way off from the actual points. Another important factor is that predetermined points were actually located off the map boundary. This made it difficult to originally mark them accurately. We were also not able to have information about the slope of the area or an aerial image that could have been used to located the points easier.