Abstract
Digital imagery and remote sensing have become popular and accessible tools in many scientiic research
ields. Accuracy of classiication, the degree of agreement between classiication and ground truth, is
traditionally quantiied by an error matrix and summarized using agreement measures such as Cohen’s
kappa. he kappa statistic, however, can be shown to be a transformation of the marginal proportions
commonly referred to as omissional and commissional error rates. Alternative estimation methods
for these agreement measures include binomial, bootstrap and Bayesian techniques. In this study, we
develop a Bayesian estimation method for omissional and commissional errors and discuss its utilization
in variability assessment and inference. We will also show how additional or sequential information
may be incorporated to improve the estimation situation. Techniques are demonstrated using previously
published data.
Application of Bayesian Methods for Assessing Detection Accuracy in
Remote Sensing
Publication History:
Received: June 10, 2016
Accepted: August 04, 2016
Published: August 06, 2016
Keywords:
Bayesian estimation, Agreement
measures, Error rates
Research Article Open Access
Introduction
In remote sensing, accuracy of classiication is traditionally
assessed by the comparison of classiied pixels with ground truth
using agreement measures such as Cohen’s kappa. Conventionally,
statistical inferences concerning the agreement measures have been
based on asymptotic normality assumptions. While asymptotic
methods may produce satisfactory results in certain instances, they
fail to account for the underlying distribution of the classiied data.
his can result in poor and inconsistent inferences regarding the
classiication accuracy.
Accuracy of classiication is oten represented in the form of an
error matrix [1, 2]. he rows of this table (i=1, 2, 3, ..., C) represent the
computer or human generated classiication and the columns (j=1, 2,
3, ..., C) denote the reference or ground truth categories:
where, x
ii
is the number of pixels correctly classiied in category i,
N
i.
and N
.i
are the corresponding marginal totals for classiication and
ground truth, respectively, and N = ΣN
i.
= ΣN
.i
.
Various methods have been suggested for assessing the degree
of ground truth agreement for each category. Common measures
include conditional kappa, a general index of agreement [3]:
,
the omissional error rate, measuring the proportion of pixels
incorrectly omitted from a classiication:
,
*
Corresponding Author: Dr. Bahman Shaii, Statistical Programs, P.O.
Box 442337, University of Idaho, Moscow, ID, 83844-2337 USA, E-mail:
bshaii@uidaho.edu
Citation: Shaii B, Price WJ (2016) Application of Bayesian Methods for
Assessing Detection Accuracy in Remote Sensing. Int J Appl Exp Math 1: 106.
doi: http://dx.doi.org/10.15344/ijaem/2016/106
Copyright: © 2016 Shaii et al. This is an open-access article distributed
under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the
original author and source are credited.
International Journal of
Applied & Experimental Mathematics
Bahman Shaii* and William J. Price
Statistical Programs, P.O. Box 442337, University of Idaho, Moscow, ID, 83844-2337, USA
Int J Appl Exp Math IJAEM, an open access journal
Volume 1. 2016. 106
Shaii et al., Int J Appl Exp Math 2016, 1: 106
http://dx.doi.org/10.15344/ijaem/2016/106
and the commissional error rate, measuring the proportion of pixels
erroneously committed to a classiication category [4]:
,
where x
ii
⁄ N
.i
and x
ii
⁄ N
i.
are commonly referred to as producer’s
and user’s accuracies [5].
he kappa statistic has been suggested as a means of assessing
the degree of agreement in remotely sensed data because it equally
weighs both omissional and commissional errors [6]. Remote sensing,
however, presents a unique situation for conditional kappa in which,
for a given image classiication, the marginal ground truth totals, N
.i
, as well as classiied totals for each class, N
i.
, are constant. Under
these conditions, (1) becomes a simple monotonic function of the
omissional error rate [7]. It should also be noted that, although kappa
treats misclassiications equally, in many cases it may be important
to distinguish between the error types [8]. For these reasons, it will
be more advantageous to carry out accuracy assessment based on the
later two measures, namely O
l
and O
l
Using Bayesian estimation and maximum entropy, Shaii et al,
[9] developed a methodology that may be used for estimation and
inference regarding the aforementioned agreement measures.
Furthermore, it has been shown that the Bayesian estimation
technique is superior to that of the exact binomial, and that due to its
ability to incorporate prior information, it can be more advantageous
than the parametric bootstrapping technique [10].
In this paper, we review the Bayesian estimation technique for
omissional and commissional error rates and illustrate its inferential
use for image variability assessment and comparison. Furthermore,
1 2 3 ... C
1 x11 x12 x13 ... x 1c N1.
2 x21 x22 x23 ... x 2c N2.
3 x31 x32 x33 ... x 3c N3.
C xc1 xc2 xc3 ... xcc NC.
N.1 N.2 N.3 ... N.C N
...
...
...
...
...
...
...
Ground Truth
ˆ
.
O 1
ii
l
i
x
N
= −
ˆ
ˆ
.
.
.
1
ii i
i
l
i
x N
N N
N
N
κ
−
=
−
ˆ
.
C 1
ii
l
i
x
N
= −
ˆ