Elevation Map Creation
To begin the process of setting up the deep soil warming experiment at the site we wanted to produce a map of the varying elevations (also known a topographic map) across the area of the site. This map will help to understand the variations in slope to help better select the locations for the experimental plots where the soil warming will take place. This process happened over three steps, measuring and "gridding" out the site, taking elevation measurements using a scope and stadia rod, and inputting map data to create a map in MatLAB.
We began by measuring the area of the site using a transect tape (Figure 1). Once we knew the approximate size of the area (about 220m squared) we were able to divided the site into smaller subplots (or grid cells) of 2x2m to create a evenly spaced grid of the site. This "gridding" process is used in surveying to make sure there is consistency in the elevation measurements, allowing for easy plot creation later on. The north to south grid lines were labeled with the alphabet letters A -K, while the east to west grid lines were labeled numerically 1-11. This resulted in each 2x2m "cell" of the grid to have its own unique letter-number label to mark its location on the map (Figure 2).
Figure 1: Measuring out the area of the site using a transect tape to establish grid size.
Figure 2: Placing the flags in for the labels of the grid. Each "cell" of the grid was 2x2m and labeled with a letter and number corresponding to there location
After we measured out the grid and labeled each cell we were able to start surveying the elevation! The elevation is measured using a level and stadia rod. The level is the eyepiece shown in Figure 3 that the surveyor looks though to at the stadia rod to get the elevation measurement. The stadia rod is a long graduated measuring rod that measures the heights of marked points from a datum or a point of known elevation. We measured the elevation at all the labeled points of the grid and recorded them to be inputed into the map.
Figure 3: The surveying level in the foreground and Casey getting the stadia rod set up in the background.
Figure 4: Making sure the surveying level is level for an accurate can be a long and tedious process for the novice surveyor.
From the data we collected we developed a map of elevation in MatLAB (Figure 5 and 6). Special thanks for to the UH Manoa Civil Engineering Department for lending us the equipment to produce our map and to Dr. Roger Babcock for the short refresher lesson on surveying!
Figure 5: 3D Surface map of the Lyon Arboretum soil warming site
Figure 6: Heat map of the Lyon Arboretum soil warming site. The heat map legend is in meters, showing contours every 0.5m. The black dots are the locations of each flag signifying a new grid point.
