Lab 12: Data Collection Using ArcPad and a Trimble Juno GPS Unit

 Introduction:

Figure 1: A Trimble Juno with ArcPad software, used for data collection

Throughout the semester, we have had several activities held at the Priory in Eau Claire, Wisconsin, a piece of property acquired by UWEC that is being used as the daycare center that was formerly located in the old education building on campus. A tour of the location can be seen by viewing the video on the right. In addition to the physical building on site, which used to be a monastery, an extensive nature area exists, which served as the location to be test the accuracy of our maps.. With each visit came an increase in our familiarity of the area, features in the environment, and other things that come with repeated exploration of a new place. Using this knowledge, we were tasked with mapping features at the Priory by using a Trimble Juno, seen in Figure 1. In order to accurately do this, a geodatabase needed to be built, containing the features to be collected. From there, the geodatabase would be deployed to the Juno unit, and the data collection could take place. Once accomplished, the data would then be exported into ArcGIS 10.1 for manipulation. The collection of this data by each group can then be used in clean-up projects that desperately need to be done at the Priory. This blog post will detail the process of doing this, and demonstrate the result of the data collection.

Methodology:

Figure 2: A TruPulse Laser, used to gather height, distance, and azimuth values

For our specified features to be mapped, our group decided to map dead trees, standing and fallen. Two features classes were created in a geodatabase with a variety of fields needed for each one, and then projected in NAD 1983 HARN Wisconsin TM coordinate system. Our group was interested in height, trunk diameter, woodpecker use, fungal presense, decomposition and placement of the trunk of the fallen trees, and leaf type of the standing trees. Each field was added to the appropriate feature class, and then domains and subtypes were attached to each of the fields. Domains and subtypes allow for a sort of feature class within a feature class function in which each field has a set of choices associated with it. For instance, the decomposition field was broken into three categories, 1 being light, 2 being medium, and 3 being heavy decomposition. Adding these domains and subtypes allowed for the user to select one of the numbers, instead of manually entering 'light', 'medium', or 'heavy', saving a considerable amount of time. .The last step was to add a base layer to serve as a reference point on the map that was going to be displayed on the Juno. The Eau Claire West, Southeast Quadrant aerial photo was used for this purpose, providing a good deal of detail on the Priory and the surrounding area. The geodatabase, complete with features and base layer, was then imported into ArcMap and saved as a map document. By using the ArcPad Data Manager, the features and basemap were then transferred to the Trimble Juno to be used in the field. Data collection consisted of getting GPS points by standing near the tree, measuring the trunk diameter by using a tape measure, and getting tree height and azimuth values of fallen trees by using a TruPulse laser, seen in Figure 2.

Figure 3: Bearing Distance to Line tool used in the activity

After data collection, the collected features were then imported into ArcMap for manipulation. Having the geodatabase set up made this very simple, with the only real task that needed to be done was finding the X and Y coordinates of the fallen trees to run the Bearing Distance To Line tool. This was done by adding X and Y fields to the Fallen Tree feature class, and then using the distance values provided in ArcMap to add the appropriate values for the corresponding tree. Using these values, and the length and azimuth fields recorded by the TruPulse, the Bearing Distance to Line tool, seen in Figure 3, could then be used to compute the size of the fallen tree and its direction on the ground, as seen in Figure 4.
 

Figure 4: Output of the Bearing Distance to Line tool, showing the direction of the trunk of the fallen tree

 Discussion:

 Using the data collected, a number of maps were able to be created demonstrating the various characteristics of the trees examines. Figures 5 and 6 show the presence or absence of fungus growing on the dead trees.  Figure 7 displays if the trees that were still standing had evidence of woodpecker use, as dead trees are popular nesting sights for woodpeckers. Figure 8 demonstrates the decomposition level of the fallen trees, with 1 being light, 2 being moderate, and 3 being heavy. And finally, Figure 9 shows the leaf type of the standing tree, either coniferous or deciduous. With the exception of one tree, all of the trees examined were deciduous. These maps can be used to investigate subjects like woodpecker habitat in the woods surrounding the Priory, or for determining the location of fallen trees and positioning of the logs for cleaning up the grounds.

Figure 5: Fungal presence of dead trees

Figure 6: Fungal presence of fallen dead trees

Figure 7: Woodpecker use of standing dead trees

Figure 8: Decomposition levels of fallen dead trees

Figure 9: Leaf types of the fallen trees

Conclusion:

This activity was another great exercise in preparing for a field exercise. Having to sit down and plan out the various fields that each feature class completely organized an otherwise chaotic experience. Having each field that we were interested in included in the geodatabase told us exactly what we wanted to examine while in the field, allowing us to start collecting data as soon as we got to the site. Ensuring that the ArcPad file worked prior to going out in the field was extremely important to the process, as this also allowed for immediate data collection. Knowing that the program was going to work exactly as it was designed to was a great feeling, as that would be one thing that would not have to be fixed in the field. All of this preparation led to a straightforward data collection with no real issues. While these maps are by no means a comprehensive list of all of the dead trees at the Priory, the database can be expanded at any time to include all of the trees if that was something that was determined to have importance. Having experience with both the Trimble Juno and the TruPulse laser certainly helped with the process as well, cutting down on the learning curve and allowing us to smoothly collect the values we needed in order to get the desired data.