# Mapping and Assessment of Tree Roots Using Ground Penetrating Radar with Low-Cost GPS

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## Abstract

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## 1. Introduction

## 2. Aims and Objectives

## 3. Survey Site and Data Acquisition

## 4. Data Processing and Methodology

#### 4.1. Radargram Signal Processing

#### 4.2. Post-Processing of the Tracking Position

#### 4.3. Kirchhoff Migration

## 5. Results and Discussion

#### 5.1. 3D Migration Result

#### 5.2. 3D Roots Detection Result

## 6. Conclusions

## Author Contributions

## Funding

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) Surveying scenario of the Metasequoia trees using the proposed 3D GPR system. (

**b**) The low-cost GlobalSat GPS receiver used in this investigation.

**Figure 2.**Time-domain reflectometry (TDR) measurements of the soil moisture for the estimation of the subsurface velocity in the site.

**Figure 3.**Raw radargram of the tree root investigation using a 500 MHz RAMAC shielded antenna system.

**Figure 4.**(

**a**) The location of the GEONET stations in Japan; (

**b**) location of the investigation site and nearest GEONET Station.

**Figure 5.**(

**a**) GPS receiver geometry with a reference station; (

**b**) flowchart of the GPS receiver bias estimation and removal by use of the Kalman filter.

**Figure 6.**Moving trajectories of antennas recorded by the GlobalSat GPS receiver. (

**a**) The record by the GlobalSat GPS receiver; (

**b**) post-processing results.

**Figure 7.**Migrated vertical profiles along the survey direction. (

**a**) Migrated profile at 0.8 m cross-survey direction; (

**b**) migrated profile at 1.6 m cross-survey direction; (

**c**) migrated profile at 2.4 m cross-survey direction; (

**d**) migrated profile at 3.2 m cross-survey direction.

**Figure 8.**Migrated horizontal slices at different depths. Red lines indicate the detected roots in the migrated data set. (

**a**) Migrated slice at 16-cm depth; (

**b**) migrated slice at 19-cm depth; (

**c**) migrated slice at 27.5-cm depth.

**Figure 9.**Migrated horizontal slices at different depths. Red lines indicate the detected roots in the migrated data set. (

**a**) Migrated slice at 42-cm depth; (

**b**) migrated slice at 59-cm depth; (

**c**) migrated slice at 79.5-cm depth.

**Figure 10.**The coarse root detection in a 3D migrated cubic: (

**a**) B-scan profile which contains a tree root. (

**b**) Root extension tracking with the −3 dB positions of a local peak (survey direction). (

**c**) Root extension tracking with the −3 dB positions of a local peak (cross-survey direction).

**Figure 11.**The reconstructed 3D root system: (

**a**) View from the starting point; (

**b**) view from the ending point.

**Table 1.**System parameters of the RAMAC 500 MHz Shielded Antenna system used for investigation purposes [27].

Parameters | RAMAC 500 MHz Shielded Antenna |
---|---|

Limit frequency lower than −10 dB: ${\mathrm{F}}_{Low}$ | 138 MHz |

Limit frequency higher than −10 dB: ${\mathrm{F}}_{High}$ | 591 MHz |

Bandwidth of −10 dB: ${B}_{-10dB}$ | 453 MHz |

Center frequency: ${F}_{Center}$ | 364 MHz |

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**MDPI and ACS Style**

Zou, L.; Wang, Y.; Giannakis, I.; Tosti, F.; Alani, A.M.; Sato, M.
Mapping and Assessment of Tree Roots Using Ground Penetrating Radar with Low-Cost GPS. *Remote Sens.* **2020**, *12*, 1300.
https://doi.org/10.3390/rs12081300

**AMA Style**

Zou L, Wang Y, Giannakis I, Tosti F, Alani AM, Sato M.
Mapping and Assessment of Tree Roots Using Ground Penetrating Radar with Low-Cost GPS. *Remote Sensing*. 2020; 12(8):1300.
https://doi.org/10.3390/rs12081300

**Chicago/Turabian Style**

Zou, Lilong, Yan Wang, Iraklis Giannakis, Fabio Tosti, Amir M. Alani, and Motoyuki Sato.
2020. "Mapping and Assessment of Tree Roots Using Ground Penetrating Radar with Low-Cost GPS" *Remote Sensing* 12, no. 8: 1300.
https://doi.org/10.3390/rs12081300