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This paper presents an experimental study of air-to-ground channels over sea surface at the C-band (5.7 GHz) with low airborne altitudes (0.37–1.83 km) through wideband channel measurements. In this paper, the multipath statistics and the propagation loss at different airborne altitudes are estimated and analyzed. It is observed that about 95% (86%) of the(More)
This paper investigates the dynamic property of a tropical forested channel due to the weather effect on very high frequency (VHF) and ultrahigh frequency (UHF) radio-wave propagation. In this paper, continuous-wave (CW) envelope fading waveforms are recorded over a period of 50 s with static antennas. This paper focuses on the analysis of the combined(More)
Near sea-surface line-of-sight (LoS) radiowave propagation at 5 GHz was investigated through narrowband measurements in this paper. Results of the received signal strength with a transmission distance of up to 10 km were examined against free space loss model and 2-ray path loss model. The experimental results have good agreement with the predicted values(More)
This paper presents a study of propagation through a typical coconut plantation for frequencies in the range of 40 MHz to 1400 MHz. Measurements of continuous-wave (CW) waveforms are used to construct the distribution functions for the fast fading characteristics of the channel. It is found to be Rician distributed. Analysis of the Rician K factor(More)
Gamma model is fitted using the second, fourth, and sixth moments to model the rain drop size distribution (DSD) of Singapore. As the Joss distrometer measures the number of rain drops between the drop diameters from 0.3 to 5 mm, the truncated moment fitting between these drop diameter ranges is also used for modeling the DSD. Gamma DSD requires(More)
Cloud imaging using ground-based whole sky imagers is essential for a fine-grained understanding of cloud formations, which can be useful in many applications. Some such imagers are available commercially, but their cost is relatively high, and their flexibility is limited. Therefore, we built a new daytime Whole Sky Imager (WSI) called Wide Angle(More)
Sky/cloud imaging using ground-based Whole Sky Imagers (WSI) is a cost-effective means to understanding cloud cover and weather patterns. The accurate segmentation of clouds in these images is a challenging task, as clouds do not possess any clear structure. Several algorithms using different color models have been proposed in the literature. This paper(More)
Ground-based whole sky imagers are popular for monitoring cloud formations, which is necessary for various applications. We present two new Wide Angle High-Resolution Sky Imaging System (WAHRSIS) models, which were designed especially to withstand the hot and humid climate of Singapore. The first uses a fully sealed casing, whose interior temperature is(More)
We propose a modified texton-based classification approach that integrates both color and texture information for improved classification results. We test our proposed method for the task of cloud classification on SWIMCAT, a large new database of cloud images taken with a ground-based sky imager, with very good results. We perform an extensive evaluation,(More)