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© 2013, IJARCSSE All Rights Reserved Page | 10
Volume 3, Issue 11, November 2013 ISSN: 2277 128X
International Journal of Advanced Research in Computer Science and Software Engineering Research Paper Available online at: www.ijarcsse.com
An Effective Multi-feature Fusion Object-based Classification Method on
ArcGIS Platform Using Very High-resolution Remote Sensing Image Ling Zhang
* Mariofanna Milanova
Department of IT Service Department of Computer Science
City of Houston, USA University of Arkansas at Little Rock, USA
Abstract— We propose a novel, multi-feature fusion, object-based classification approach on the ESRI ArcGIS
platform using very high resolution remote sensing imagery for the study area of Lake Maumelle watershed,
Arkansas, USA. The Lake Maumelle watershed contains a reservoir that provides drinking water for more than
400,000 people in the Little Rock metropolitan area. The reservoir has a long history of excellent water quality.
However, suburban and urban development is increasing within the watershed, prompting concerns that land use
changes will impact water quality. The goal of this research is to build an easy to use tool to help water resource
managers detect land use changes within the watershed. We suggest that the integration of GIS and Remote Sensing
technologies on a single GIS platform could be a cost - effective approach in terms of time and money. The image
classification method includes four steps. First, texture features of the image are extracted, analyzed, and composited
into the original image. The original image is a color-infrared aerial imagery with one foot ground resolution
acquired in 2009. Second, we use an ESRI ArcObjects Model based on a multiresolution statistical segmentation
algorithm to generate regions. Third, training samples and test samples are generated using ESRI ArcMap and visual
inspection of the image. Next, a supervised support vector machine (SVM) classifier is applied to the segmented
multi-feature fusion and mulit–channels image. Fourth, classification accuracy is assessed with the test samples using
a tool developed in ArcGIS platform. The experiment achieved a high overall accuracy of 94.44 with 0.91 Kappa
value, which indicated an excellent probability that image pixels were correctly classified.
Keywords— GIS, remote sensing, segmentation, classification, texture
I. INTRODUCTION
There is a need for user-friendly processes to detect land use changes for water resources managers. Land use in the
Lake Maumelle watershed, Arkansas, USA, is expected to undergo significant changes in the next several decades, with
residential developments replacing forest in many areas. These land use changes have the potential to increase pollutant
loads and degrade water quality in the lake. Detecting the land use and land cover (LULC) changes is therefore a critical
requirement for the monitoring of the hydrology and water quality of the watershed and developing effective land
management and planning strategies. Current methods for detecting LULC changes require technical expertise, the use of
multiple software platforms and can be quite expensive in terms of both time and money. The traditional approach uses
visual interpretations of remote sensing data to search and identify changes, followed by manual editing of the LULC
feature class using geographic information systems (GIS) software. For Lake Maumelle, the existing LULC GIS database
was obtained with the help of 2009 color infrared one foot resolution orthophotos using unsupervised classification in
ERDAS imagine image processing software and digitizing the classified features using ArcGIS software. Image
classification refers to the task of extracting information classes from a multiband raster image [1]. It is a process used to
convert remotely sensed data into meaningful information. Post-classification comparison is a popular change detection
technique [2]. A highly accurate image classification of LULC is the key to the success of change detection in the study
area.
We are going to use the same image dataset that were used to develop existing LULC GIS database for our project.
Very high resolution imagery (VHRI) can provide much more detailed ground truth and much better visualization.
However, due to the fact that complexity and redundancy of the very high resolution imagery (VHRI) is greatly increased
and detailed information such as spectral, shape, context, and texture are provided by VHRI, traditional pixel-based
image classification approaches may not be feasible for VHRI and cannot provide satisfying results. Object – based
approaches can overcome the limitations of pixel-based methods applied to VHRI. Therefore, in this paper, we propose a
multi-feature fusing, object-based classification method, which uses texture feature fusing, image segmentation based on
multispectral statistics and image object shape measurement, and supervised support vector machine classification.
These components are implemented and deployed on the ESRI ArcGIS 10 platform. The integration of image processing
and GIS on a single software platform can save both time and money. We will use a 2009 color infrared orthophoto with
1 foot ground resolution as sample image data and a LULC feature class from the existing LULC GIS database that
covers the sample area for our proposed classification method experiment.
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 11
II. IMAGERY DATA AND ITS NDVI AND TEXTURE FEATURES
The original image is a color-infrared aerial image with one foot ground resolution acquired in 2009. It contains three
individual bands being sensitive to red, green, and near infrared wavelengths. Near infrared (NIR) wavelengths are
slightly longer than red, and they are outside of the range visible to the human eye. Blue wavelengths are filtered out of
CIR. Conventionally, a CIR image is set up to display the infrared band data with a red tone. Red wavelengths will
appear green, and green wavelengths will appear blue. Blue wavelengths are not displayed. Because the healthy green
vegetation will appear to be bright red, a CIR image is also known as a “false colour” image. CIR tends to penetrate
atmospheric haze better than natural colour, and it provides sharper imagery [3].
The Normalized Difference Vegetation Index (NDVI) is an important feature of digital CIR data, and is one of the
major attributes for representing vegetation conditions, and it is widely utilized to distinguish the vegetation covered
surface and non-vegetation covered surface [3].
The formula is:
NDVI = (NIR –Red)/(NIR + Red),
where NIR is the Near Infrared channel, and Red is the Red channel. The NDVI image is generated using ArcGIS NDVI
function. Fig. 2.1 shows the original CIR aerial photo and its NDVI image.
Fig. 2.1 Original CIR image (left) and NDVI image (right)
The textural features of image contain information about the spatial distribution of spectral variability within a
band. Texture is one of the important characteristics used in identifying objects or regions of interest in an image. Grey
Level Co-occurrence Matrices (GLCM) is one of the earliest methods for texture feature extraction proposed by Haralick
et al., in 1973 [4] and is one of the most popular methods used for describing texture. This method looks at computing a
spatial dependence probability distribution matrix [4]. This method assumes that information about image texture is
adequately specified by the matrix of relative frequencies Pij with the two gray cells separated by a distance d and an
angle alpha occur on the image, one with the gray level i and the other with the gray level j [4]. Using the gray level
spatial dependence matrices various texture features like energy, entropy, contrast, homogeneity and correlation are
calculated. Such textural descriptors are still developed today to give more and more powerful tools for classification
tasks or segmentation problems [5].
In order to describe how gray level co-occurrence matrices work, we let I(x, y: 0 ≤ x ≤N-1, 0 ≤ y ≤N-1) be used to
represent an image of size N * N with G gray levels. The image I with G gray levels is quantized to Ng levels, and let Lx
= {1, 2, 3…, Nx} be used to represent the horizontal spatial domain (range of pixel values) and Ly = {1, 2, 3…, Ny} be
used to represent the vertical spatial domain [4].
The image block used to derive gray level co-occurrence matrices is based on the nearest neighbourhood resolution
cells [4]. The neighbourhood resolution cells for a pixel * at I(x, y) are shown in Fig. 2.2.
Fig. 2.2 Resolution cells 1 and 5 are horizontal nearest neighbours to resolution cell *; resolution cells 2 and 6 are 135°
nearest neighbours; resolution cells 3 and 7 are 90° nearest neighbours; and resolution cells 4 and 8 are 45° nearest
neighbours to * [4].
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 12
In this method it is assumed that texture information is adequately specified by a matrix of relative frequencies Pij
where two neighbouring resolution cells that are separated by a distance d and an angle α occur in the image block, one
with a gray level i and the other with a gray level j [4]. These matrices are therefore a function of the angular relationship
between neighbouring cells as well as the distance between the cells [4].
Mathematically this relationship can be represented as:
P (i, j, d, 0°) = # {((k, l), (m, n) Є N, where k – m = 0, |l – n| = d
P (i, j, d, 45°) = # {((k, l), (m, n) Є N, where k – m = d, l – n = -d
P (i, j, d, 90°) = # {((k, l), (m, n) Є N, where |k – m| = d, l – n = 0
P (i, j, d, 135°) = # {((k, l), (m, n) Є N, where k – m = -d, l – n = d
where # represents the number of elements in the set, and k, l, m, n Є G and I (k, l) = i, I (m, n) = j.
To illustrate the above with an example, let us consider a simple 4 * 4 image chip with 3 gray levels:
The gray level co-occurrence matrices for the above image chip where d = 1 and α = 0°, 90°, 45° and 135°
respectively are shown below:
P(0°, H) P(90°,V) P(45°,RD) P(135°,LD)
The gray tone spatial-dependence matrix (GLCM) can be computed after the neighbourhood resolution cells for a
pixel have been obtained. The gray level co-occurrence matrix will be normalized by the sum of all the elements in the
co-occurrence matrix [4].
Haralick defined a total of 14 parameters from the co-occurrence matrix. Only five of them - homogeneity and angular
second moment, contrast, correlation, Entropy, local homogeneity (dissimility) are commonly used because it was shown
that the other out of the 14 are highly correlated with each other, and that the 5 indicated sufficed to give good results in a
classification task [6]. The homogeneity and angular second moment is a measure of similarity in pixel values of the
neighbourhood resolution cells in an image block [4]. The contrast feature is a measure of the amount of local variations
present in an image [4]. The correlation measure is a measure or predictability of pixel values in the horizontal and
vertical domains. It could also be described as a measure of linear dependencies in an image [4]. Entropy can be
described as a measure of the complexity or the measure of information in an image. The greater the variations in the
neighbourhood resolution cells, the greater the entropy values [4].
The following table (Table 1) lists 5 Haralick’s texture feature equations.
TABLE I: HARALICK’S TEXTURE FEATURE EQUATIONS
Name Equation Equation #
Angular Second Moment
(1)
Contrast
(2)
Correlation
(3)
Inverse Difference Moment (Dissimility)
(4)
Entropy
(5)
1 1 0 0
1 1 0 0
0 2 2 2
3 3 2 2
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 13
P(i,j) is the (ith
, jth
) entry in the normalized co-occurrence matrix; Ng is the dimension of co-occurrence matrix; Pᵪ(i)
and Pᵧ(j) are the marginal probabilities.
𝜇𝑥 , 𝜇𝑦 are the means of pₓ and pᵧ:
σᵪ and σᵧ are the standard deviations of Pᵪ and Pᵧ:
In our method, we propose to use standard deviation of pixel values in the neighbourhood to extract texture feature
from the very high resolution remotely sensed imagery using Block Statistics tools in ArcGIS.
The equations
(6)
σ(і,ј) is the standard deviations of P(i,j) of the N x N neighbourhood. The normalization function can be a mean filter:
𝑦 𝑖, 𝑗 = 𝑋 𝑖 − 𝑚, 𝑗 − 𝑛 ∗ 𝑅(𝑚, 𝑛)1𝑛=−1
1𝑚=−1 (7)
The Block Statistics tool in ArcGIS 10 performs a neighborhood operation that calculates a statistic for input cells
within a fixed set of non-overlapping windows or neighborhoods. The standard deviation is calculated for all input cells
contained within each neighborhood. The resulting value for an individual neighborhood or block is assigned to all cell
locations contained in the minimum bounding rectangle of the specified neighborhood. For a 5 * 5 image block, the
standard deviation image block is illustrated as Fig. 2.3:
III. SEGMENTATION
Segmentation refers to the process of partitioning a digital image into non-intersectable regions, in the way that each
region is homogeneous and that union of. It is an essential step toward higher level image processing [7]. Because very
high resolution remotely sensed imagery contains much more complexity and redundancy of spectrum, shape, texture,
the traditional pixel based classification methods tend to produce classification errors such as multiple spectral signatures
within a semantic object. Those multiple signatures, cannot be effectively dealt with by standard methods and tend to
produce “salt and pepper” classification results, when one semantic object is composed of multiple spectral signatures [8].
Baatz et al., proposed the multiresolution segmentation algorithm, in which the concept of the “degree of fitting” was
defined [9].
= (𝑓1𝑑 − 𝑓2𝑑 )2𝑑 (8)
The distance can be furthermore standardized by the standard deviation over all segments of the feature in each
dimension.
= 𝑓1𝑑−𝑓2𝑑
𝜎𝑓𝑑
2
𝑑 (9)
Appropriate object features can be mean spectral values or texture features such as the variance of spectral values
[9].
The degree of fitting of two adjacent image objects can be defined by describing the change of heterogeneity in a
virtual merge and generalized to an arbitrary number of channels c, each having a weight Wϲ:
(10)
Appropriate definitions for spectral heterogeneity of image objects can be the variance of spectral mean values or the
standard deviation spectral mean values [9].
Changhui et al., defined the distance of two regions in their research:
2 5 7 8 8
6 6 7 9 9
5 5 4 9 9
4 6 3 2 2
6 6 9 9 9
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
2 2 2 2 2
Fig. 2.3 original 5x5 image block Standard deviation image block
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 14
(11)
Ii and Ij are the average spectral value of two regions. If the spectral differences between neighbour regions are smaller
than the threshold, the regions would merged be together [10].
The eCognition commercial software adopts the Fractal Net Evolution Approach for segmentation, which is a
region merging technique based on a pairwise region merging. The merging criterion is that the average heterogeneity of
image objects weighted by their size in pixel should be minimized [9].
Due to the facts that much more efforts may be required to determine the mulitspectral difference threshold or
heterogeneity minimum threshold, we need to look at a decision to merge two regions based on spectral statistics:
(12)
is the set of regions with Ɩ pixels, , Ɩ is the total number of pixels in the image. is the total
number of pixels in this region R, , g = 256, is a set of independent random variables with
values in [0, g/ ]. The merging predicate is:
(13)
denotes the observed average for channel a in region R [11].
This algorithm is able to capture the main structural components of imagery using a simple but effective statistical
analysis, and it has the ability to cope with significant noise corruption, handle occlusions with the sort function, and
perform multi-scale segmentation. But it has the shortage of under-segmentation [12].
In very high resolution remote sensing images, the image objects that represent ground geographic features or
objects are clear. Therefore, we must handle the image objects homogeneity or heterogeneity during the process of region
merging. Shape is an important property of an object in an image. It can be used to measure the homogeneity or
heterogeneity of image objects that represent the geographic features.
Shape heterogeneity can be described by the difference of degree of compactness and/0r degree of smoothness
before and after two adjacent regions are merged [9]. Compactness represents the cluster degree of the pixels in the
region. Smooth degree indicates the smoothness of the region boundary. Shape criteria can reduce the disturbance from
noise and fragments and result in more regular objects [13].
(14)
where c is the compactness, is the perimeter, and A the object area.
(15)
where s is the smoothness, is the perimeter, and b is the perimeter of the region bounding box [13].
(16)
are weight values about compact heterogeneity and smooth heterogeneity respectively [13].
For two adjacent regions intending to merge, the merge criteria based on shape heterogeneity can be:
(17)
For each band of a multispectral image data, the general heterogeneity is:
(18)
In the study area, less than 10% land use are urban areas, where most of shapes are more regular such as linear
(roads), square or rectangles (residential or commercial areas) with smoother edges than other geographic features.
Around these paved or unpaved areas are bare-ground features with lighter colours. Forest, water bodies, and rooftops
have darker colours. Therefore, the shape criteria for two regions to be merging are set to be dynamic. For developed
areas and their surrounding areas, the shape threshold for merging two regions will be high. A non-linear function will
give the shape threshold based on the average spectral values of two regions to be determined to merge. The formula and
Fig. 3.1 graph for the function are:
(19)
where d is initial value of parameter, when R =255 , W < d , to avoid possible ln(0), If ,(RMax R ) < 10 then
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 15
Fig. 3.1 Graph for formula (19)
Finally, for an arbitrary number of channels c and at n scale, we have a formula from formula (17) and (12):
(20)
Fig. 3.2 shows the flowchart of multiresolution statistical segmentation.
Scale < n ?
Merge regions
yes
High resolution
remote sensing
data
Segmented image
Merge predicate: spectral statistics and
shape heterogeneity
yes
no
Fig. 3.2 Mulitresolution statistical segmentation flowchart
IV. CLASSIFICATION
Support vector machine (SVM) technique has advantages in remote sensing: (a). It has the ability to generalize well
from a limited amount and / or quality of training data. This property is particularly appealing in the remote sensing field
in that training samples and ground truthing are limited and expensive [14]. (b) it is a non-parametric learning technique,
therefore there is no assumption made on the underlying data distribution. This is particularly appealing in remote
sensing applications since data acquired from remotely sensed imagery usually have unknown distributions [15]. (c). It
can produce higher classification accuracy than the traditional methods such as maximum likelihood estimation [16],
decision trees, neural networks k-nearest neighbour (k-NN), training data-driven fuzzy classifiers [17]-[19]. (d). It can
incorporate texture properties well and achieve higher classification performance with image texture [26] and in the
object – based classification approaches [25][27][28].
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 16
In addition, the SVM algorithm for data classification is based on structural risk minimization (SRM) principle.
SVM can handle large input spaces, which means it is good for processing remote sensing data. It can effectively avoid
overfitting by controlling the margin, and automatically identify a small subset made up of informative points – support
vectors. The Support vector machine classification technique has been widely used in land cover land use tasks
[29][30][31], forest species classification [32][33][34], and urban areas[35][36][37].
Here is the basic idea behind SVM for pattern recognition. For the two-class classification problem, support vector
machine is a linear two-class classifier. Given a set of samples:
𝑀 = 𝑥1 , 𝑦1 , 𝑥2 , 𝑦2 , … , 𝑥𝑖 , 𝑦𝑖 , i is the number of the samples i = 1, 2, 3, ….l,
𝑥𝑖𝜖 𝑅𝑛
and
𝑦 𝜖 {+1, −1}𝑙 Here, +1 and -1 indicate the two classes. The processing of classification is to produce a solution function:
𝑓 𝑥 : 𝑥𝑖 → 𝑦
For any other model of x, f(x) can produce the corresponding values of y better. In the condition that a linear separation is
possible, we have the solution as shown in Fig. 4.1
Fig. 4.1 The separating hyperplanes.
For a dataset such as shown in Figure 4.1 is linearly separable, there exist many such hyperplanes that can separate
the two classes correctly. So we have the question that which hyperplane to choose to ensure not only the training data,
but the future examples as well, are classified correctly. Support vector machine (SVM) can achieve the hyperplane that
is known as maximal margin hyperplane which is maximally distant from the two class data. Fig. 4.2 shows maximal
margin hyperplane. In Figure 4.2, we let the L- to be ⍵·x + b = -1, and L+ to be ⍵•x + b = +1, then the maximal margin
hyperplane can be expressed as to L0 = ⍵·x + b = 0, where is the weight vector of classification’s surface, and the scalar
b is called the bias. The interval between the two classes is 2
||⍵||, which is the distance between L- and L+. The calculation
of the maximal margin hyperplane can be formulated to be the following optimization problem:
minω,b 𝜔 2
Subject to 𝑦𝑖 ⍵ · 𝑥𝑖 + 𝑏 ≥ 1, 𝑖 = 1,2,··· 𝑛 (21)
Let to be the solution of the above optimization problem. The maximal margin hyperplane can be expressed
by , and the classification decision function can be formulated by [32].
Fig. 4.2 The maximal margin hyperplane
The training samples which satisfy the equation are named support vectors. To optimize, the
Lagrange function can be converted to Quadratic programming [32].
(22)
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 17
Where αi ≥ 0 is named Lagrange multiplier. The objective function and constraints can be expressed by the equation (23).
max 𝐿 𝜶 = 𝜶𝑖 −1
2
𝒏
𝒋=𝟏
𝒏
𝒊=𝟏
𝑛
𝑖=1
𝒚𝒊𝒚𝒋𝜶𝒊𝜶𝒋𝒙𝒊 ∙ 𝒙𝒋 subject to 𝜶𝑖𝑦𝑖
𝑛
𝑖=1
= 0, 0 ≤ 𝜶𝑖 ≤ 𝐶 (23)
If we let 𝛼𝑖∗ to be the optimal solution, then ⍵∗ = 𝛼𝑖
∗𝑛𝑖=1 𝑦𝑖𝑥𝑖 and the optimal classification decision can be
calculated by the equation (24).
𝐿 = 𝛼𝑖𝑦𝑖𝑥𝑖𝑇𝑥𝑗 + 𝑏 𝑏 = 𝑦𝑖 − 𝛼𝑖𝑦𝑖𝑥𝑖
𝑇𝑥𝑗
(24)
In many applications, if a linear separation is not possible, a non-linear function can provide better accuracy by
mapping the train samples into high-dimensional feature space in which the linear separation of the train samples is
possible. To do so, a function: 𝜙 𝑥 is introduced. The mapping is performed by a kernel function
which defines an inner product in the higher dimension space. Therefore, the optimal classification decision
function implemented by SVM can be written as equation (25) [32].
𝑓 𝑥 = 𝑠𝑔𝑛( 𝛼𝑖∗𝑦𝑖𝑘 𝑥𝑖 , 𝑥𝑗 + 𝑏∗
𝑘
𝑖=0
)
(25)
The can be unknown exactly to use the equation (25). The kernel function 𝑘 𝑥𝑖 , 𝑥𝑗 can do it. There are two
typical kernel functions: polynomial kernel (equation 26) and Radial Basic function (RBF) kernel (equation 27)
𝑘 𝑥𝑖 , 𝑥𝑗 = ( 𝑥𝑖 , 𝑥𝑗 + 𝑟)𝑑 (26)
𝑘 𝑥𝑖 , 𝑥𝑗 = exp −ϓ 𝑥𝑖 − 𝑥𝑗 2
, ϓ > 0 (27)
ϓ, d, r are kernel parameters.
V. EXPERIMENT
We extracted the standard deviation texture feature image. After inspecting the histogram, statistics and images of
the five types of texture images - angular second moment, contrast, dissimility, entropy and correlation, we make a
comparison with angular second moment, contrast, dissimility (Table II, Fig. 5.1 – Fig. 5.4)
Fig. 5.1 standard deviation texture feature (left) and Contrast texture feature image (right)
Fig. 5.2 dissimility (inverse difference moment) texture feature (left) and angular second moment texture feature (right)
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 18
Fig. 5.3 Histograms of contrast texture feature (left) and standard deviation texture feature (right)
Fig. 5.4 Histograms of angular second moment texture feature (left) and dissimility texture feature (right)
TABLE II
TEXTURE FEATURES IMAGES STATISTICS
Texture feature Maximum Minimum Mean Std dev.
Standard Deviation 255 0 38.8 24.2
Contrast 255 0 12 22.75
Angular second
moment
1 0 0.19 0.83
Dissimility 32 0 1.99 1.97
We found the standard deviation texture feature is similar to contrast texture features.
Histogram of g25demoenvctrstgray.tif: Field = VALUE
Distribution based on display resolution
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
Histogram of g25demosecmgray.tif: Field = VALUE
Distribution based on display resolution
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
Histogram of g25demoenvdisgry.tif: Field = VALUE
Distribution based on display resolution
50,000
45,000
40,000
35,000
30,000
25,000
20,000
15,000
10,000
5,000
0
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 19
We implemented multiresolution statistical segmentation algorithm using ArcObjects Model on ArcGIS version 10.
Fig. 5.6 shows an example of a segmented image at resolution 2400 pixels (top) and 800 pixels (bottom).
Fig. 5.6 segmented imagery at 2400 pixels resolution (upper) and 800 pixels resolution (lower).
We also used the algorithm to segment texture feature and NDVI images. Fig. 5.7 shows a segmented NDVI image
at 1600 pixels resolution and 400 pixels resolution. Fig. 5.8 shows a segmented standard deviation texture feature image
at 1600 pixels resolution and 400 pixels resolution.
Fig. 5.7 Segmented NDVI image at 1600 pixels resolution (bottom) and 400 pixels resolution (top).
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 20
Fig. 5.8 segmented standard deviation texture feature at 1600 pixels resolution (top) and 400 pixels resolution (bottom).
There are six categories of land use land cover in the area of the experiment aerial photo according to the existing
LULC GIS database (Table 3).
TABLE III: LULC TYPES IN THE EXPERIMENT AERIAL PHOTO AREA
LULC types Coniferous
forest
Deciduous
forest
Pasture/bare
ground
Lake/pond Paved
surface
Rooftop
class C4 C2 C1 C3 C5 C7
acres 402 0.51 74.7 5.8 313.9 0.46
percentage 50.4% 0.06% 9.4% 0.73% 39.3% 0.06%
We created 30 training sample points for each type using the Create Random Points tool in ArcMap, which
generated about 0.032% sampling pixels relative to the total number of pixels in the test image. An ArcPy tool using
LIBSVM [33][34] with RBF was used to process the SVM classification with the segmented image that was fusioned
with the standard deviation texture feature and NDVI images. Fig. 5.10 shows the classification result image.
Fig. 5.10 classification result image
Zhang et al., International Journal of Advanced Research in Computer Science and Software Engineering 3(11),
November - 2013, pp. 10-23
© 2013, IJARCSSE All Rights Reserved Page | 21
VI. ACCURACY ASSESSMENT
We generated about 30 test points for each classification types using Create Random Points tool in ArcMap and
visual inspection on the image. The accuracy of classifications was measured using the overall accuracy.
Given the error matrix N = (nij), the overall accuracy is defined as
(28)
Where |T| is the number of pixels we are testing.
Given the error matrix with r rows, the Kappa statistic is defined as:
(29)
where i = 1, 2,3…., r , and r is the number of rows in the matrix, X ii s the number of observations in row i and column i,
Xi+ = ∑Xj+ , and X+i = ∑Xik are the marginal totals for row i and column i respectively, and N is the total number of the
observations.
Using an accuracy assessment tool developed with ArcPy in ArcGIS, we obtained an error matrix (Table 4),
including overall, user's, and producer's accuracies, as well as Kappa statistic for a given classification based on test data.
TABLE IV: ERROR MATRIX
C4 C1 C3 C2 C5 C7 UT UP
C4 366 14 0 0 1 0 381 96.06
C1 4 301 0 0 6 0 311 96.78
C3 0 0 27 0 0 0 311 100
C2 12 7 0 55 0 0 74 74.32
C5 0 1 0 0 14 0 15 93.33
C7 0 1 0 0 0 18 19 94.74
PT 382 324 27 55 21 18 827 0.00
PP 95.81 92.90 100 100.00 66.67 100.00 0.00 94.44
UT is user's total, PT is producer's total, and UP and PP are corresponding percentages. The results were a 94.44
overall accuracy and 0.91 Kappa value. The assessment results indicate we achieved an excellent probability that the
image pixels were correctly classified with very strong agreement.
VII. CONCLUSIONS
In this paper, we propose a novel, multi-feature fusion, object-based classification approach on the ESRI ArcGIS 10
platform using very high resolution remote sensing imagery for the study area of Lake Maumelle watershed, Arkansas,
USA. There is only one supervised, pixel-based classification method – The Maximum Likelihood Classification, and
one unsupervised classification method - ISO Cluster unsupervised Classification in ArcGIS software. We extracted
standard deviation texture feature and NDVI feature images from original image data and fusioned into original image
data. We implemented multiresolution statistical segmentation algorithm on ArcGIS 10 platform. The multiresolution
statistical segmentation algorithm improved the existing statistical region merge model with image objects shape
heterogeneity dynamic thresholds, which overcame the advantage of under-segmentation. The SVM with the RBF kernel
function are used to classify the image objects or regions produced by the multiresolution statistical segmentation process.
Our experiment proved the proposed approach can achieve high classification performance for very high resolution
remotely sensed image. The method greatly improves the processing speed of the SVM training and classifying. This
method is based on the integration of GIS and Remote Sensing technologies on a single GIS platform, which can be a
cost - effective approach in terms of time and money.
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