Using GIS to Investigate Urban Forestry

1. Data Collection with GPS Receiver and dbh Tape

1. In an open outdoor location, turn on the GPS receiver by pressing the power button. Wait 2-3 min while receiver connects to a minimum of three satellites.
2. Walk to the survey area for data collection. Survey one city block segment at a time and number the parkway trees on a data sheet (Figure 1), resetting the numbering at the start of each block segment.
3. At each tree in the survey, record species, postal address (e.g., 1253 W. Lill), and geodesic coordinates (longitude/latitude) provided by the GPS receiver (Figure 1). Ensure geodesic coordinates are collected from the same direction at each tree (e.g., north side of each tree).
4. Measure the diameter of each tree at 4½ ft above the ground and record the diameter at breast height (dbh).
5. Observe each tree condition by visually estimating and scoring according to the criteria (Table 1). Sum the points for one overall score for each tree and assign each tree to the corresponding health categories. Record health condition on the data sheet.

2. Entering Data into a GIS

1. GIS using Google Earth: Type in the tree coordinates and save them in the “My Places” folder using the “Add Placemark” feature. Name each tree by species name. Once all tree data points are saved as placemarks, right-click on the My Places name, select “Save As,” and save to any location.
2. GIS using ESRI ArcGIS 10.2: To import into ArcGIS, ensure all column headings have no spaces; any spaces should be replaced with underscores. If the coordinates are in latitude/longitude, they should be in decimal degrees (DD) format before importing into ArcGIS. Locations in degrees, minutes and seconds (DMS) or decimal minutes (DM) format should be converted to DD first. There are converters available on the internet (http://www.fcc.gov/encyclopedia/degrees-minutes-seconds-tofrom-decimal-degrees).
3. Save/export the data as a comma-delimited text file (CSV format).
4. Create a “layer” by adding the .csv file to ArcMap by using the Add data tool, either by expanding the submenu under File> Add Data or by clicking the Add Data tool on the Standard toolbar (Figure 2).
5. Right-click on the new layer and choose Display XY Data. Ensure that the X and Y fields were selected correctly by ArcMap – they should be right if the names chosen reflect the coordinate positions (northing and easting or x and y).
6. Click the Edit… button, then Select… to select the coordinate system for the points, Add… and OK (3x). The correct coordinate system to use may be obtained from the GPS unit (under map setup or units). For this data, select Coordinate Systems > Geographic Coordinate Systems > World > WGS1984.prj (default GPS datum).
7. There should now be a point layer at the top of the Table of Contents with the same name as the .csv file and the word Events on the end of the name (Figure 3). This is an “event theme” and is a temporary layer. For a more permanent copy, right-click on the layer and choose Data > Export Data… Pick an output location — a geodatabase feature class or a directory for a shapefile — and enter a file name. Change the name from the default “Export_Output” to Urban_Forestry_Survey. Click OK.

3. National Tree Benefits Calculator

1. Using this software, the benefits of street-side trees can be calculated. This includes a tree’s annual benefits for storm water management, property value, energy efficiency, and carbon sequestration. See the video Tree Identification: How to Use a Dichotomous Key for instructions on using the Tree Benefits Calculator.

Figure 1. Representative results for street trees found one block.

Figure 2. The Add Data tool on the Standard toolbar.

Figure 3. Point layer at the top of the Table of Contents with the same name as the CSV file.

Table 1.  A table to calculate the condition class of a tree. Each condition score correlates with its description in each category, then all six scores are totaled for a final sum – the condition class.