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Empirical model for total precipitable water retrieval from ground-based GNSS observations in Thailand
(2020-08-14)
Rangsanseri, Yuttapong
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Phasamak, Weeranat
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Soisuvarn, Seubson
Retrieval of Total Precipitable Water (TPW) from ground-based Global Navigation Satellite System (GNSS) observations is a challenging task due to its real-time and high temporal resolution nature. In this paper, we present a method for establishing an analytical model for retrieving the TPW based on the GNSS observations over 1-year period from 12 stations distributed across Thailand. The derived Zenith Total Delay (ZTD) at all stations agrees well with the TPW data available from the Global Data Assimilation System (GDAS) Numerical Weather Prediction (NWP) model. First, a unique relationship between the ZTD and the TPW was established by taking into account the variations in station altitudes. Then, a bias correction technique with Probability Distribution Function (PDF) matching was applied to improve the final model. The inversion model of the TPW from ZTD was then easily obtained by using a numerical technique. The performance of our method has been successfully evaluated on an independent test data. This model can be useful for near real-time TPW measurements from globally available GNSS receivers.
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Experimental evaluation scheme of DTTV propagation loss in Thailand
(2019-07-01)
Promwong, Sathaporn
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Tiengthong, Thanadol
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Chaisang, Aditep
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Rangsanseri, Yuttapong
Digital terrestrial television (DTTV) propagation loss should be known characteristics of DTTV propagation channels. In Thailand used DVB-T2 standard for broadcast television channel which shell be study. DTTV propagation loss based in measurement data with system design and analysis of DTTV parameters are importance. In order to predict the result of the broadcast of DVB-T2 in Pathumthani, Thailand, the Hata propagation model is used as the calibration and optimization method for the measurement results. The measurement of the DVB-T2 signal which broadcast from transmitted station are collect as the source of research data. Two broadcast channels were sampling as the broadcasting frequency in this research, i.e., 626 MHz (CH40) and 658 MHz (CH44). The separated distance between transmitted station and received antenna were in range of 2 km. to 7 km. The least square method is use as the optimized propagation model of DVB-T2 signal. The mean error and root mean square error are use as the statistical value for the calibrated model, while relative error is use to indicate the comparison of model component. In the DTTV propagation channel analysis, the root means square error and the optimized method of calibrated model has relative error higher than the calibrated model with mean error. From the results, it shows that the calibrated model of Hata propagation model with mean error is suitable for predict DTTV propagation loss in urban area of Thailand.
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Determination of total precipitable water from GNSS data in Thailand
(2019-01-01)
Phasamak, Weeranat
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Soisuvarn, Seubson
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Rangsanseri, Yuttapong
The relationship between the total precipitable water (TPW) in the atmosphere and Global Navigation Satellite System (GNSS) Zenith Total Delay (ZTD) has been investigated. The study was performed for ZTD observations derived from GPS measurements at 5 sites across Thailand, over one-year period, July 2017 to August 2018. The ZTD was then collocated in space and time with the TPW data available from Global Data Assimilation System (GDAS) Numerical Weather Prediction (NWP) model. The result showed that the ZTD observations are highly correlated with the TPW but there are some biases between the ground base station locations largely due to the altitude differences. An empirical model was then developed to remove the altitude dependence and provide a unique relationship between the ZTD and the TPW. This model can be useful in the further TPW measurements from widely available GNSS receivers.
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Automatic scaling of critical frequency fof2 from ionograms based on a pixel-following technique
(2018-01-01)
Rangsanseri, Yuttapong
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Phasamak, Weeranat
This paper proposes a new technique for automatic scaling of critical frequency foF2 parameter of F2-layer from ionograms. Scaling of ionograms initially had to rely on experienced staff for manual operation. In this paper, we have examined ionograms data collected at Chumphon, Thailand, in March 2015, during the period that the observed F2 layer traces can be identified. Our method extracts foF2 value by finding a pixel on the beginning of the trace line and will use this pixel as the starting point for finding the ends of the traces by scanning either one or two lines. In each step we need to prepare the ionogram image, remove unnecessary part of image then remove noise, and refill the trace line before final scanning process. Based on a pixel-following technique, the method produces high accuracy results because it can scan until the final pixel of the trace line. The proposed method has been successfully tested on various ionograms, the results match with a single-pixel accuracy comparing to manual scaling.
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Remote sensing image retrieval using DCT-based texture descriptor
(2016-01-01)
Nuangnit, Atcharawan
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Rangsanseri, Yuttapong
In this paper, we propose an image retrieval technique using texture descriptor extracted from a block-based Discrete Cosine Transform (DCT) of the image. To construct the texture descriptor, the absolute DCT coefficients are averaged over the entire image, and the feature vector is formed up by choosing middle-frequency elements of the zigzag-scanned DCT coefficients. This extraction is applied to both query image and all images in the archive. A distance function is used to measure the similarity between two images. This technique is successfully applied to remote sensing images downloaded from www.earthexpolrer.usgs.gov of Thailand regions.
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ACS watermarking based on texture analysis in DCT domain
(2010-12-01)
Promcharoen, Somying
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Rangsanseri, Yuttapong
In this paper, we propose a new approach for digital image watermarking in DCT domain. A texture analysis is applied on each 8x8 DCT blocks in order to classify the block as texture or non-texture region. The Ant Colony System Algorithms (ACSs) are then performed to find out the optimal parameters for watermark embedding, independently for each region type. The experimental results show that the proposed approach yields a watermark that is invisible to human eyes and robust to various image manipulations. The algorithm was also compared with the previous work, and our algorithm is superior for all test images.
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Relevance-weighted (2D)2LDA image projection technique for face recognition
(2009-08-01)
Sanayha, Waiyawut
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Rangsanseri, Yuttapong
In this paper, a novel image projection technique for face recognition application is proposed which is based on linear discriminant analysis (LDA) combined with the relevance-weighted (RW) method. The projection is performed through 2-directional and 2-dimensional LDA, or (2D)2LDA, which simultaneously works in row and column directions to solve the small sample size problem. Moreover, a weighted discriminant hyperplane is used in the between-class scatter matrix, and an RW method is used in the within-class scatter matrix to weigh the information to resolve confusable data in these classes. This technique is called the relevance-weighted (2D)2LDA, or RW(2D) 2LDA, which is used for a more accurate discriminant decision than that produced by the conventional LDA or 2DLDA. The proposed technique has been successfully tested on four face databases. Experimental results indicate that the proposed RW(2D)2LDA algorithm is more computationally efficient than the conventional algorithms because it has fewer features and faster times. It can also improve performance and has a maximum recognition rate of over 97%. © 2009.
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Weighted LDA image projection technique for face recognition
(2009-01-01)
Sanayha, Waiyawut
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Rangsanseri, Yuttapong
In this paper, we propose a novel image projection technique for face recognition applications based on Fisher Linear Discriminant Analysis (LDA). The projection is performed through a couple subspace analysis for overcoming the "small sample size" problem. Also, weighted pairwise discriminant hyperplanes are used in order to provide a more accurate discriminant decision than that produced by the conventional LDA. The proposed technique has been successfully tested on three face databases. Experimental results indicate that the proposed algorithm outperforms the conventional algorithms. Copyright © 2009 The Institute of Electronics, Information and Communication Engineers.
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Genetic watermarking based on texture analysis in DCT domain
(2008-12-01)
Promcharoen, Somying
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Rangsanseri, Yuttapong
In this paper, we propose a new approach for digital image watermarking in DCT domain. A texture analysis is applied on each 8×8 DCT blocks in order to classify the block as texture or non-texture region. The Genetic Algorithms (GAs) are then performed to find out the optimal parameters for watermark embedding, independently for each region type. The experimental results show that the proposed approach yields a watermark that is invisible to human eyes and robust to various image manipulations. The algorithm was also compared with the previous work, and our algorithm is superior for all test images. © 2008 SICE.
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Genetic watermarking with block-based DCT clustering
(2008-12-01)
Promcharoen, Somying
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Rangsanseri, Yuttapong
In this paper, we propose a new approach for digital image watermarking in DCT domain. This approach used a Fuzzy C-Mean algorithm (FCM) to classify 8x8 DCT blocks as texture or non texture region. The Genetic Algorithms (GAs) are then performed to find out the optimal parameters for watermark embedding, independently for each region type. The experimental results show that the proposed approach yields a watermark that is invisible to human eyes and robust to various image manipulations. The algorithm was also compared with the previous work, and our algorithm is superior for all test images. © 2008 IEEE.

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