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1 Introduction
On the last years there was an elevated increase on the civil
construction field (a 42.41% increase between 2004 and 2010),
being able to keep the extension between 4% and 5% for the
next years [1]. In the same rate grows the number of edifications
that present structural alterations, for project upgrades and en-
vironmental changes reasons. In this context, there is a growing
concern with the inspection of the masonry and concrete struc-
tures that may present modification or visible damages along
the time.
The cracks analysis is an important security issue to be valued
on civil engineering structures inspections [2], [3] and [4]. The
masonry constructions inspection allows observing the stabil-
ity or the increase of the opening of crack that can indicate the
necessity for structural repairs. The crack opening term involves
the opening of one or more cracks on masonry and concrete.
The crack opening alteration is a referential item on the techni-
cian’s analysis on periodic structural inspections. The inspec-
tion on the damaged structure is accomplished on different peri-
ods to the identification of possible cracks alterations.
A crack opening constant monitoring method is the use of the
mechanical or electrical strain gages, installed between two
damaged structures. On another method, the conventional mea-
surement is obtained by an inspection technician, with a dimen-
sional metrology instrument manually placed on the damaged
structure. On the reading of a crack opening, the technician ob-
serves on the instrument the measuring trait and the scale value
correspondent to the crack opening.
The direct observation on conventional measuring is a very
thorough and exhausting task, and it depends on the techni-
cian’s experience. Besides that, factors as tiredness, fatigue
and distractions can contribute to different crack dimensions
registers from the actual dimension. Although this manual tech-
nique is known and low priced, the time requested for measure-
ment and the imprecision on the results have been motivating
the researches for automatic methods.
The present paper’s objective is to contribute with a tool for
comparative analysis of the crack opening on masonry and
concrete. The purpose is to reduce the inspection technician’s
workload, facilitating and presenting more exact and consistent
results (smaller repeatability error).
Many works have been proposing the automation of the identifi-
cation and valuation of the increase rate of cracks on masonry.
Some works have utilized video images, applying color contrast
techniques between concrete and grout aggregates [5], and on
the detection of crack on pavement artificial neural networks
were used [6]. However, other works have used image process-
ing routines in order to identify cracks on masonry, with Fourier
analysis application [7], and on cracks edges detection apply-
ing image binarization techniques [8], [9] and [10]. Images of
surfaces on masonry prepared with fluorescence marker were
analyzed for micro-cracks’ detection [11]. Spatial filters on col-
ored image were applied to perform the crack region separa-
tion from the rest of the image [12]. The Sobel and Canny edge
detectors, associated to the Fast Fourier transform [13], were
used to identify the region occupied by masonry cracks. With
an image processing algorithm applying the Hough transform,
the verification of the crack’s length and width (opening) were
obtained [14]. Canny’s edge detector and Otsu’s thresholding
[15] were utilized to identify cracks on concrete tubes. Cam-
eras’ optical measuring and Green-Lagrange’s expression [16]
are tools that were applied to measurement on cracks. Texture
filters on the interest surface area [17] were used for crack iden-
tification. With webcams and images tools’ from Matlab software
[18], it is possible to find and measure the masonry’s cracks.
On the math algorithm applying [19] occurs cracks’ detection
by the difference of reflections of thermographic light radiation
from the masonry intact area. The cracks are also identified by
an algorithm applying a median filter on the image [20]. The
digital photogrammetry techniques [21] and [22] are utilized to
measure the cracks’ dimensions and to estimate civil engineer-
ing structural deformations.
Despite the accuracy and consistency of the results presented
by the discussed proposals, the performance of most of the au-
tomatic systems is presented utilizing a fixed platform to ac-
complish the measurement. Specifically, the fixed platform is
composed of a video camera to the image acquisition and a
personal computer (PC) to execute the processing algorithms
and image analysis. This requirement contributes to the partial
restriction of the use of these methods in research laboratories
or specifics environments.
The increase of the data processing and data storage capacity,
associated to the integration of high resolution video cameras
on the modern mobile phones with low prices, have been al-
lowed the substantial enlargement of these sophisticated mobile
devices’ applications. Accordingly, this article proposes the au-
tomation of the masonry and concrete cracks dimensional com-
paring (structural masonry or closure masonry), starting with the
hardware and software integration in only one mobile platform.
To reach such objective, this proposal used as mobile platform
the mobile phone Samsung model Omnia WSGH-i677 UG, 1.4
GHz processor and 512 MB (RAM) and Windows Phone 7.5
operational system.
In this paper an important contribution is the reduction of the
technician subjectivity on the monitoring of the crack opening
and the uncertain statistics, when compared to the conven-
tional method.
Although the mobile platforms processing capacity has in-
creased during the last years, the image processing algorithm
originally developed on PC software are still computationally
more complex to be executed directly on mobile phones. In this
context, the optimization of an image processing algorithm, typi-
cally utilized on PC, in a way that it may be executed on a mobile
phone, represents another important contribution of this work.
The article is organized as follows. The Section 2 presents the
necessary procedures on the conventional measurement on the
evaluation of the masonry crack’s growth. The proposed moni-
toring system is described on Section 3. The Section 4 presents
the image digital processing and the Section 5 discusses the
obtained results. The conclusions are on Section 6.
2. Conventional method
On a conventional procedure, the inspection technician veri-
fies the growth of the crack opening through a period of time, by
means of manual measurement. This kind of manual measuring on
415 IBRACON Structures and Materials Journal • 2013 • vol. 6 • nº 3
A. P. Martins | J. C. Pizolato Junior | V. L. Belini