Article Figures & Data
Figures
- Figure 1.
Example layout of sidewalk, GPR paths, and resulting scan sections used in analysis. Trees are surrounded by 8 sampling sections (labeled 1-8). GPR scans ran across the sidewalk as a width scan and along the sidewalk length (labeled long GPR scan). Tree openings were 0.25 m2, and not to scale in the above image. As length and width scans overlapped on corner sections (1, 3, 6, and 8), the two GPR data outputs were averaged in analysis.
- Figure 2.
GPR Roots Inspection System. The SIR-3000 Control Computer is at the top with its sun shield. The radar antenna is the module in the white tub (which maintains contact with the ground surface). An encoder wheel rubs against the cart’s right rear wheel to provide distance information for automatic data collection.
- Figure 3.
a) Field layout of the tree-sidewalk study plot. b) Air excavation of entire root system grown in CU-Soil. c) Root system during removal of roots <0.8 cm.
- Figure 4.
Regression output showing confidence and prediction intervals for a relationship in CU-Structural Soil comparing ground-penetrating radar output to excavated actual root counts (N = 40 measurement sections, not all data points visible due to overlap). Relationship shown: excavated root count = 0.97 + 0.83 radar signal count; r2 = 0.81.
- Figure 5.
Regression output showing confidence and prediction intervals for a relationship in compacted soil comparing ground penetrating radar output to excavated actual root counts (N = 40 measurement sections, not all data points visible due to overlap). Relationship shown: Excavated root count = −0.12 + 0.77 radar signal count; r2 = 0.76.
Tables
- Table 1.
Regression models to relate excavated root counts of trees in two pavement treatments as compared to ground penetrating radar counts of root signals. As a ground-truth verification study, the expected slope would be equal to 1 (one root for each signal) with an intercept of zero. In the regression models presented, y = excavated root count, and x = GPR count.
Model Equation n S.E. slope p-value Ho slope = 1.0 S. E. constant p-value Ho constant = 0 r2 Experiment-wide (mixed effect model) y = 0.84x + 0.26 80 0.05 0.004 0.36 0.4765 0.88 CU-Soil scan section y = 0.83x + 0.97 40 0.07 0.022 0.46 0.435 0.81 tree y = 0.96x + 3.8 5 0.23 0.87 10.21 0.735 0.86 Silt loam scan section y = 0.77x − 0.12 40 0.09 0.017 0.43 0.7846 0.76 tree y = 2.13x − 40.6 5 0.95 0.30 26.1 0.217 0.63 - Table 2.
Whole-tree (as total of eight count zones) root radar signal count versus actual root count. Positive numbers are overestimation of root count by radar and negative numbers are underestimation of root count by radar. Zero would be parity in grand totals between radar signal and root count, but not necessarily within count zones.
Tree replicate 1 2 3 4 5 CU-Soil excavated root count 38 57 43 49 47 radar signal count 40 56 39 45 43 difference 2 -1 -4 -4 -4 Compacted soil excavated root count 12 10 17 17 33 radar signal count 28 26 25 25 33 difference 16 16 8 8 0
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