Jian-ao Lian

A UGV-based laser scanner system for measuring tree geometric characteristics

This paper introduces a laser scanner based measurement system for measuring crop/tree geometric characteristics. The measurement system, which is mounted on a Unmanned Ground Vehicle (UGV), contains a SICK LMS511 PRO laser scanner, a GPS, and a computer. The LMS511 PRO scans objects within distance up to 80 meters with a scanning frequency of 25 up to 100Hz and with an angular resolution of 0.1667° up to 1°. With an Ethernet connection, this scanner can output the measured values in real time. The UGV is a WIFI based remotely controlled agricultural robotics system. During field tests, the laser scanner was mounted on the UGV vertically to scan crops or trees. The UGV moved along the row direction with certain average travel speed. The experimental results show that the UGVs travel speed significantly affects the measurement accuracy. A slower speed produces more accurate measuring results. With the developed measurement system, crop/tree canopy height, width, and volume can be accurately measured in a real-time manner. With a higher spatial resolution, the original data set may even provide useful information in predicting crop/tree growth and productivity. In summary, the UGV based measurement system developed in this research can measure the crop/tree geometric characteristics with good accuracy and will work as a step stone for our future UGV based intelligent agriculture system, which will include variable rate spray and crop/tree growth and productivity prediction through analyzing the measured results of the laser scanner system.

Dilation-3 PR QMF for image processing

Perfect reconstruction (PR) quadrature mirror filter (QMF) banks with finite impulse response (FIR) filters are constructed from systems of dilation-3 biorthogonal refinable functions and wavelets. Such filters can be applied to image processing applications, such as image compression, image denoising, etc. These filters are linear due to the symmetry property of their underline biorthogonal refinable functions and wavelets, which satisfy functional equations with dilation factor 3. Image compression experiments show that the proposed dilation-3 QMFs outperform the popular CDF 9/7 filter bank.

Image object removal in redundant wavelet transform domain

In this paper, we present a novel approach on image object removal by extending subpatch texture synthesis technique into redundant wavelet transform (RDWT) domain. As an overcompleted wavelet transform, RDWT is shift invariant and obtained without downsampling. Also, each RDWT highpass subband exhibits one specific orientation features of the image, in horizontal, vertical, or diagonal. All these make RDWT ideal for performing texture synthesis object removal techniques. In our experiments, subpatch texture synthesis in RDWT is introduced to remove unwanted objects from digital photographs. Specifically, for each RDWT subband, depending on the subband orientation, a particular direction subpatch texture synthesis is applied independently. Experimental results reveal that our simple algorithm performs better than previous methods.