Introduction
A combination of social,
economic, legal, and administrative parameters leads, in several countries, to
the stage of unplanned development and to the creation of a considerable number
of illegal buildings.
When increased in number, they may create various problems such as:
·
Decrease
of state and local revenue since they are not fully taxed, as the illegal
buildings are not registered, but they also demand additional infrastructure
and services provision.
·
Serious
social and economic impact on the owners and on the national economy, and the
real estate market. The owners may be charged with high penalties, also such
properties cannot be transferred or mortgaged, while there is always a risk of
creating an informal market, and
·
In
the case of a massive scale, they may have a negative environmental effect.
·
The
illegitimate nature of the buildings also poses a safety threat to the
residents of the buildings and the people living near such illegally
constructed buildings, as it is difficult to verify if the building was
constructed following the Building Safety Codes of the region.
Governments
have applied high penalties in case of the detection of illegal constructions,
but this alone cannot solve the problem. Sound update of land-use planning according
to changing needs, and a series of other fiscal and social measures are also
necessary.
From
a technical point of view, one common reason for the administration’s
inefficiency to control unplanned development is the difficulty to locate
quickly, and in time, the under-construction illegal buildings in a
cost-effective way and stop the construction at its beginning or apply a
penalty within a short time after its completion.
Classic
administrative control procedures are proved inefficient, especially when
public administration suffers from a lack of employees, bureaucracy, and
increased responsibilities. It is difficult to place inspectors at each area to
stop illegal construction work and this will encourage corruption.
The
contribution of modern techniques and tools is necessary for the design of an
automated and objective procedure for the detection of informal constructions.
The
adjacent images show how the aerial view changes with time when the region is
undergoing urbanization. Identifying these changes and matching them with
municipal records can help in identifying illegal buildings.
Informal
Settlements
·
As
per legal framework in most of the countries, “informal construction” is
characterized by any construction which
* exists without a building permit,
* has any kind of excess or violation to the building permit,
* is in violation of any valid urban and spatial regulation regardless of the
existence of a building permit.
·
The
focus of this project is restricted only to the 1st category – constructions
without a building permit- and on buildings at the urban fringe or generally in
areas without urban plans, which gradually create unplanned settlements.
·
The
term “urban plan” refers to a formal set of rules and plans, which define the
zoning and building regulations to be applied on both the private plots and the
plots selected for common use and common benefit activities.
·
In
areas without urban plan construction is only permitted inland parcels bigger
than 0.4 ha and only for a building size up to 200 sq.m.
·
Also,
these land parcels must not have been characterized as archaeological sites,
forest land, environmentally sensitive areas, and they should not be under any
other protection restrictions, e.g., those for coastal zones.
·
Informal
settlements in many countries do not have the characteristics of slums.
·
The
quality of construction and the living conditions in these areas are of a
satisfactory or even high level.
·
Also,
illegal constructions have never created major conflict or violence with the
state, mainly because they are built on legally owned land parcels.
·
The
lack of cadastre in such countries has a multidimensional impact on land
management issues.
·
It
is the major factor that makes spatial planning procedure extremely time and
cost consuming, and it allows the creation of informal settlements since there
is no other tool available for environmental and development monitoring.
·
Also,
there is no other system for reliable statistical spatial data provided to
support the development of land, the real estate market, and decision making
for applying sound land use regulations and efficient land policy.
·
The
prior sample shows a rather typical example of unplanned urban sprawl in an
area of Central Greece. This area is approx. 1.5 km from the sea and is
characterized as agricultural land.
·
Many
land parcels though are small (most are under the minimum area size for a
building permit) and gradually not cultivated.
·
Until
recently most construction there was exclusively for vacation purposes. The
construction development in the sample area is observed in four different time
periods.
·
Aerial
photos of years 1975, 1980, 1989, and a satellite image of 2001 are shown.
·
All
construction made before 1974 was legal, since the government, for a short
period, gave permits for vacation houses in smaller parcels. The later
government changed these regulations, to require all new construction to be on
parcels of 4,000 sq.m or greater.
·
The
upper left area of the photos, with a dense road network, shows a part of the sample
area which has a formal urban plan where development of land is permitted even
inland parcels of an area size of 500 sq.m. All the remaining area is outside
of the urban plan.
·
Observation
of the above four images shows that:
* In 1975 all area was agricultural land with very few buildings used for
agricultural purposes. Very few vacation houses appeared due to the temporary
governmental decision to permit this type of construction.
* In 1980 more buildings appear: those legal within the urban plan, where
construction is comparatively larger and denser, and those informal within the
‘outside urban plan’ area.
* In 1989 almost all area within the formal urban plan has been developed
legally. There is a significant development within the neighboring area where
no urban plan exists; the majority of these buildings are informal, built
without a building permit.
* In 2001 informal development within the area without urban plan becomes even
denser. It is obvious that informal development was continued and it increased
during the last decade and with even higher rates.
Available
Platform and High-Resolution Data
·
Today
a wide variety of sensors and platforms is available, providing many choices of
high-resolution imagery suitable for digital detection of buildings and other
man-made constructions or physical elements.
·
The
scope of this project is the detection of illegal buildings, with a minimum
area size of TBD (example -30 sq.m) and planimetric accuracy of the final
photogrammetric product (vector plot or orthophoto) of TBD (example – 1m).
·
Sensors
that meet these technical specifications basically can be divided into two
broad categories: airborne and spaceborne.
·
Concerning
airborne sensors, aerial cameras are the standard choice for very
high-resolution imagery.
·
Digital
aerial cameras, in particular, are becoming popular since they have significant
advantages over their film-based predecessors. These cameras:
* ensure a continuous digital workflow from data acquisition to data
processing, and
* are not influenced by grain and usually have better radiometric resolution
than film cameras.
·
Spaceborne
sensors are also a good source for high-resolution image data. Satellite images
may have lower ground resolution than aerial images, but they cost less and
each scene covers a larger area.
·
Very
high-resolution spaceborne systems like IKONOS-2, QuickBird-2, and OrbView-3
provide panchromatic images with 0.82m, 0.62m, and 1m ground resolution, for
nadir view, respectively.
·
New
generation satellites like EROS-C, OrbView-5, and WorldView-1 provide a higher
ground resolution of about 0.4m-0.7m, and real-time transmission of imagery,
making spaceborne systems even more attractive.
Change Detection
Strategies
·
Monitoring
the suburban environment for illegal buildings is, in fact, a change detection
problem augmented by some spatial information concerning land use zones and
building regulations. The solutions proposed to the problem depend on the image
scale.
·
For
monitoring illegal urbanization, first, buildings are extracted and then they
are back-projected to the reference data where it is determined if there has
been a change.
·
The
prior sample shows a rather typical example of unplanned urban sprawl in an
area of Central Greece. This area is approx. 1.5 km from the sea and is
characterized as agricultural land.
·
Many
land parcels though are small (most are under the minimum area size for a
building permit) and gradually not cultivated.
·
Until
recently most construction there was exclusively for vacation purposes. The
construction development in the sample area is observed in four different time
periods.
·
Aerial
photos of the years 1975, 1980, 1989, and a satellite image of 2001 are shown.
·
All
construction made before 1974 was legal, since the government, for a short
period, gave permits for vacation houses in smaller parcels. The later
government changed these regulations, to require all new construction to be on
parcels of 4,000 sq.m or greater.
·
The
upper left area of the photos, with a dense road network, shows a part of the
sample area which has a formal urban plan where development of land is
permitted even inland parcels of an area size of 500 sq.m. All the remaining
area is outside of the urban plan.
·
Observation
of the above four images shows that:
* In 1975 all area was agricultural land with very few buildings used for
agricultural purposes. Very few vacation houses appeared due to the temporary
governmental decision to permit this type of construction.
* In 1980 more buildings appear: those legal within the urban plan, where
construction is comparatively larger and denser, and those informal within the
‘outside urban plan’ area.
* In 1989 almost all areas within the formal urban plan has been developed
legally. There is a significant development within the neighboring area where
no urban plan exists; the majority of these buildings are informal, built
without a building permit.
* In 2001 informal development within the area without urban plan becomes even
denser. It is obvious that informal development was continued and it increased
during the last decade and with even higher rates.
Available
Platform and High-Resolution Data
·
Today
a wide variety of sensors and platforms is available, providing many choices of
high-resolution imagery suitable for digital detection of buildings and other
man-made constructions or physical elements.
·
The
scope of this project is the detection of illegal buildings, with a minimum
area size of TBD (example -30 sq.m) and planimetric accuracy of the final
photogrammetric product (vector plot or orthophoto) of TBD (example – 1m).
·
Sensors
that meet these technical specifications basically can be divided into two
broad categories: airborne and spaceborne.
·
Concerning
airborne sensors, aerial cameras are the standard choice for very
high-resolution imagery.
·
Digital
aerial cameras, in particular, are becoming popular since they have significant
advantages over their film-based predecessors. These cameras:
* ensure a continuous digital workflow from data acquisition to data processing, and
* are not influenced by grain and usually have better radiometric resolution
than film cameras.
·
Spaceborne
sensors are also a good source for high-resolution image data. Satellite images
may have lower ground resolution than aerial images, but they cost less and
each scene covers a larger area.
·
Very
high-resolution spaceborne systems like IKONOS-2, QuickBird-2, and OrbView-3
provide panchromatic images with 0.82m, 0.62m, and 1m ground resolution, for
nadir view, respectively.
·
New
generation satellites like EROS-C, OrbView-5, and WorldView-1 provide a higher
ground resolution of about 0.4m-0.7m, and real-time transmission of imagery,
making spaceborne systems even more attractive.
Change
Detection Strategies
·
Monitoring
the suburban environment for illegal buildings is, in fact, a change detection
problem augmented by some spatial information concerning land use zones and
building regulations. The solutions proposed to the problem depend on the image
scale.
·
For
monitoring illegal urbanization, first, buildings are extracted and then they
are back-projected to the reference data where it is determined if there has
been a change.
Illegal
Urbanization Detection: Architecture
New
Building Detection
·
New
buildings can be identified from the combination of building detection and
change detection solutions.
·
Buildings
identified in both images can be verified to be existent on municipal records,
to determine their legitimateness.
·
This
use case mostly relies on building detection and takes help from the change
detection algorithm.
Illegal Building
Detection Using AI
·
NEW ILLEGAL BUILDING UNDER CONSTRUCTION
New
buildings can be identified from the combination of building detection and
change detection solution.
Buildings identified in both images can be verified to be existent on municipal
records, to determine their legitimateness.
This use case mostly relies on building detection and takes help from the
change detection algorithm.
·
ILLEGAL BUILDING EXTENSION
Extension
to buildings can be detected using the changes in the area of the bounding box
of the building combined with the change detection obtained difference image.
An information classifier can be built to classify these changes as to they
indicate building an extension or not.
Municipal records can help in identifying if an extension is within the
permissible range.
This solution is an equal application of both, building detection and change
detection algorithm.
·
ILLEGAL CONSTRUCTION OF RECREATIONAL AREAS
The construction of open-air recreational areas can be identified from the AI-based change detection solution.
Changes in the images over time can be classified as changes in the landscape,
which can be further enhanced by Sports Facilities detection, and any other
specific object detection solution.
This use case is a direct application of change detection and can be further
enhanced using various other object detection techniques.
Conclusion
·
Using
satellite images and data available from
the municipal records, our platform provides an automated procedure that is
easy to use, robust, and accurate enough, to meet the needs of specific
purposes.
·
It
benefits from the modern “know-how” in the monitoring of changes and in
automatic building extraction using high-resolution images.
·
Administratively,
the proposed system may be easily applied at a regional level, without
significant requirements for state acts, e.g., the new legal framework.
·
It
is cost-efficient taking into consideration the benefits of solving the problem
of loss of state revenue and the impact on the national economy such
in-formalities bring until the necessary reforms will be in place.