Ground-Based 3D Radar Imaging of Trees Using a 2D Synthetic Aperture

Justin Penner,David Long

doi:10.3390/electronics6010011

Abstract

Motivated by the desire to gain insight into the details of conventional airborne synthetic aperture radar (SAR) imaging of trees, a ground-based SAR system designed for short-range three-dimensional (3D) radar imaging is developed using a two-dimensional (2D) synthetic aperture. The heart of the system is a compact linear frequency modulation-continuous wave (LFM-CW) radar, a custom two-dimensional scan mechanism, and a three-dimensional time-domain backprojection algorithm that generates three-dimensional backscatter images at an over-sampled resolution of 10 cm by 10 cm by 10 cm. The backprojection algorithm is formulated directly in spatial coordinates. A new method for estimating and compensating for signal attenuation within the canopy is used that exploits the backprojection image formation approach. Several three-dimensional C-band backscatter images of different individual trees of multiple species are generated from data collected for trees both in isolation and near buildings. The trees imaged in this study are about 10 m in height. The transformation of the three-dimensional images to airborne SAR images is described and a sample result provided.

Highlights

Airborne synthetic aperture radar (SAR) systems have been widely used for imaging natural terrain and features [1]
As radars increase in resolution, there is interest in better understanding the interaction of the radar signal with tree foliage and how trees appear in SAR images
In an effort to better understand how trees appear in SAR images and to collect tree scattering and size data, a ground-based, short-range radar imaging system has been constructed that uses a two-dimensional (2D) synthetic aperture to create high resolution three-dimensional (3D) images of radar scattering from trees

Summary

Introduction

Airborne synthetic aperture radar (SAR) systems have been widely used for imaging natural terrain and features [1]. In an effort to better understand how trees appear in SAR images and to collect tree scattering and size data, a ground-based, short-range radar imaging system has been constructed that uses a two-dimensional (2D) synthetic aperture to create high resolution three-dimensional (3D) images of radar scattering from trees. This paper briefly describes the radar system and scanner, discusses modulation‐continuous wave (LFM‐CW) and records dechirped data to a compact flash card. The core radio frequency (RF) system is a C-band microASAR [2] that uses frequency the1.7 processing algorithm, and provides images collected of several trees. The radar illumination is from the right, so the tree’s radar to the incidence left, extends while angle layover the canopy appear to canopy the righttoofappear the base. Trees of of differing geometry observed at a at similar incidence angleangle near

Layover

Results

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10. Optical through

Conclusions