13 research outputs found
Reduced complexity turbo equalization using a dynamic Bayesian network
It is proposed that a dynamic Bayesian network (DBN) is used to perform turbo equalization in a system transmitting
information over a Rayleigh fading multipath channel. The DBN turbo equalizer (DBN-TE) is modeled on a single
directed acyclic graph by relaxing the Markov assumption and allowing weak connections to past and future states. Its
complexity is exponential in encoder constraint length and approximately linear in the channel memory length.
Results show that the performance of the DBN-TE closely matches that of a traditional turbo equalizer that uses a
maximum a posteriori equalizer and decoder pair. The DBN-TE achieves full convergence and near-optimal
performance after small number of iterations.Additional file 1: DBN-TE Pseudocode algorithm. (a) DBN-TE function
pseudocode. (b) FORWARD MESSAGE function pseudocode. (c)
BACKWARD MESSAGE function pseudocode. (d)
FORWARD BACKWARD MESSAGE function pseudocode. (e)
LLR ESTIMATES function pseudocode.http://www.hindawi.com/journals/asp/am2013ai201
Rapid detection of new and expanding human settlements in the Limpopo province of South Africa using a spatio-temporal change detection method
Recent development has identified the benefits of using hyper-temporal satellite time series data for land
cover change detection and classification in South Africa. In particular, the monitoring of human settlement
expansion in the Limpopo province is of relevance as it is the one of the most pervasive forms of
land-cover change in this province which covers an area of roughly 125 000km2. In this paper, a spatiotemporal
autocorrelation change detection (STACD) method is developed to improve the performance
of a pixel based temporal Autocorrelation change detection (TACD) method previously proposed. The
objective is to apply the algorithm to large areas to detect the conversion of natural vegetation to settlement
which is then validated by an operator using additional data (such as high resolution imagery).
Importantly, as the objective of the method is to indicate areas of potential change to operators for further
analysis, a low false alarm rate is required while achieving an acceptable probability of detection. Results
indicate that detection accuracies of 70% of new settlement instances are achievable at a false alarm rate
of less than 1% with the STACD method, an improvement of up to 17% compared to the original TACD
formulation.http://www.elsevier.com/locate/jag2016-08-30hb201
Land cover separability analysis of MODIS time series data using a combined simple harmonic oscillator and a mean reverting stochastic process
It is proposed that the time series extracted from moderate
resolution imaging spectroradiometer satellite data be modeled
as a simple harmonic oscillator with additive colored noise.
The colored noise is modeled with an Ornstein–Uhlenbeck process.
The Fourier transform and maximum-likelihood parameter estimation
are used to estimate the harmonic and noise parameters of
the colored simple harmonic oscillator. Two case studies in South
Africa show that reliable class differentiation can be obtained between
natural vegetation and settlement land cover types, when
using the parameters of the colored simple harmonic oscillator as
input features to a classifier. The two case studies were conducted
in the Gauteng and Limpopo provinces of South Africa. In the case
of the Gauteng case study, we obtained an average for
single-band classification, while standard harmonic features only
achieved an average . In conclusion, the results obtained
from the colored simple harmonic oscillator approach outperformed
standard harmonic features and the minimum distance
classifier.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=4609443ai201
An inductive approach to simulating multispectral MODIS surface reflectance time series
In this paper, a first order MODIS time series
simulator, which uses a Colored Simple Harmonic Oscillator, is
proposed. The simulated data can be used to augment data sets so
that data intensive classification and change detection algorithms
can be applied without enlarging the available ground truth data
sets. The simulator’s validity is tested by simulating data sets of
natural vegetation and human settlement areas and comparing it
to the ground truth data in the Gauteng province located in South
Africa. The difference found between the real and simulated
data sets, which is reported in the experiments is negligent. The
simulated and real world data sets are compared by using a wide
selection of class and pixel metrics. In particular the average
temporal Hellinger distance between the real and simulated data
sets is 0.2364 and 0.2269 for the vegetation and settlement class
respectively, while the average parameter Hellinger distance is
0.1835 and 0.2554 respectively.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=8859hb2013ai201
Cavalieri integration
We use Cavalieri’s principle to develop a novel integration technique
which we call Cavalieri integration. Cavalieri integrals differ from Riemann integrals
in that non-rectangular integration strips are used. In this way we can use single
Cavalieri integrals to find the areas of some interesting regions for which it is difficult
to construct single Riemann integrals.
We also present two methods of evaluating a Cavalieri integral by first transforming
it to either an equivalent Riemann or Riemann-Stieltjes integral by using special transformation functions h(x) and its inverse g(x), respectively. Interestingly enough
it is often very difficult to find the transformation function h(x), whereas it is very
simple to obtain its inverse g(x).http://www.tandfonline.com/loi/tqma20hb201
Using Page's cumulative sum test on MODIS time series to detect land-cover changes
Human settlement expansion is one of the most
pervasive forms of land cover change in South Africa. The use
of Page’s Cumulative Sum Test is proposed as a method to
detect new settlement developments in areas that were previously
covered by natural vegetation using 500 m MODIS time series
satellite data. The method is a sequential per pixel change alarm
algorithm that can take into account positive detection delay,
probability of detection and false alarm probability to construct
a threshold. Simulated change data was generated to determine a
threshold during a preliminary off-line optimization phase. After
optimization the method was evaluated on examples of known
land cover change in the Gauteng and Limpopo provinces of
South Africa. The experimental results indicated that CUSUM
performs better than band differencing in the before mentioned
study areas.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=8859hb2013ai201
The use of a multilayer perceptron for detecting new human settlements from a time series of MODIS images
This paper presents a novel land cover change detection method that employs a sliding window over hyper-temporal multi-spectral images acquired from the 7 bands of the MODerate-resolution Imaging Spectroradiometer (MODIS) land surface reflectance product. The method uses a Feedforward Multilayer Perceptron (MLP) for supervised change detection that operates on multi-spectral time series extracted with a sliding window from the dataset. The method was evaluated on both real and simulated land cover change examples. The simulated land cover change comprises of concatenated time series that are produced by blending actual time series of pixels from human settlements to those from adjacent areas covered by natural vegetation. The method employs an iteratively retrained MLP to capture all local patterns and to compensate for the time-varying climate in the geographical area. The iteratively retrained MLP was compared to a classical batch mode trained MLP. Depending on the length of the temporal sliding window used, an overall change detection accuracy between 83% and 90% was achieved. It is shown that a sliding window of 6 months using all 7 bands of MODIS data is sufficient to detect land cover change reliably. Window sizes of 18 months and longer provide minor improvements to classification accuracy and change detection performance at the cost of longer time delays.The CSIR Strategic Research Panelhttp://www.elsevier.com/locate/jagai201
Detecting land cover change using an extended Kalman filter on MODIS NDVI time-series data
A method for detecting land cover change using
NDVI time series data derived from 500m MODIS satellite
data is proposed. The algorithm acts as a per pixel change
alarm and takes as input the NDVI time series of a 3x3 grid
of MODIS pixels. The NDVI time series for each of these
pixels was modeled as a triply (mean, phase and amplitude)
modulated cosine function, and an extended Kalman Filter was
used to estimate the parameters of the modulated cosine function
through time. A spatial comparison between the center pixel
of the the 3x3 grid and each of its neighboring pixel’s mean
and amplitude parameter sequence was done to calculate a
change metric which yields a change or no-change decision after
thresholding. Although the development of new settlements is
the most prevalent form of land cover change in South Africa,
it is rarely mapped and known examples amounts to a limited
number of changed MODIS pixels. Therefore simulated change
data was generated and used for preliminary optimization of
the change detection method. After optimization the method was
evaluated on examples of known land cover change in the study
area and experimental results indicate a 89% change detection
accuracy, while a traditional annual NDVI differencing method
could only achieve a 63% change detection accuracy.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=885
Meta-optimization of the Extended Kalman filter's parameters through the use of the Bias-Variance Equilibrium Point criterion
The extraction of information on land cover classes
using unsupervised methods has always been of relevance to the
remote sensing community. In this paper, a novel criterion is proposed,
which extracts the inherent information in an unsupervised
fashion from a time series. The criterion is used to fit a parametric
model to a time series, derive the corresponding covariance matrices
of the parameters for the model, and estimate the additive noise
on the time series. The proposed criterion uses both spatial and
temporal information when estimating the covariance matrices
and can be extended to incorporate spectral information. The
algorithm used to estimate the parameters for the model is the
extended Kalman filter (EKF). An unsupervised search algorithm,
specifically designed for this criterion, is proposed in conjunction
with the criterion that is used to rapidly and efficiently estimate the
variables. The search algorithm attempts to satisfy the criterion by
employing density adaptation to the current candidate system. The
application in this paper is the use of an EKF to model Moderate
Resolution Imaging Spectroradiometer time series with a triply
modulated cosine function as the underlying model. The results
show that the criterion improved the fit of the triply modulated
cosine function by an order of magnitude on the time series over
all seven spectral bands when compared with the other methods.
The state space variables derived from the EKF are then used for
both land cover classification and land cover change detection.
The method was evaluated in the Gauteng province of South
Africa where it was found to significantly improve on land cover
classification and change detection accuracies when compared
with other methods.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=36hb201
Land cover change detection using autocorrelation analysis on MODIS time-series data : detection of new human settlements in the Gauteng province of South Africa
Human settlement expansion is one of the most pervasive
forms of land cover change in the Gauteng province of South
Africa. A method for detecting new settlement developments in
areas that are typically covered by natural vegetation using 500 m
MODIS time-series satellite data is proposed. The method is a per
pixel change alarm that uses the temporal autocorrelation to infer
a change index which yields a change or no-change decision after
thresholding. Simulated change data was generated and used to
determine a threshold during an off-line optimization phase. After
optimization the method was evaluated on examples of known land
cover change in the study area and experimental results indicate a
92% change detection accuracy with a 15% false alarm rate. The
method shows good performance when compared to a traditional
NDVI differencing method that achieved a 75% change detection
accuracy with a 24% false alarm rate for the same study area.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?reload=true&punumber=4609443hb2017Electrical, Electronic and Computer Engineerin