Download the use of satellite and aerial imagery, and gps for delineation of ea

Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
THE USE OF SATELLITE AND AERIAL
IMAGERY, AND GPS FOR
DELINEATION OF EA BOUNDARIES
Roberto Bianchini
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
Summary
1. Objectives of delineation of EA boundaries
2. Criteria for the delineation of EA boundaries
3. Main critical criterion to delineate EA boundaries
4. Principal type of maps for census operations
5. The satellite remote sensing
6. The aerial photography
7. The Global Positioning system (GPS)
8. Some conclusions
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
1. Objectives of delineation of EA boundaries
‰ To support the census coverage
‰ To support fieldwork operations
‰ To contribute to the statistical analysis at small area
level
‰ To support sampling for statistical surveys
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
2. Criteria for the delineation of EA boundaries
EAs has:
‰
To cover the entire country and do not have to overlap
‰
Be consistent with the administrative division and other
relevant geographic units
‰
To have boundaries easily identifiable on the ground
‰
To be of approximately equal population size in order to
be covered by an enumerator during data collection
(Differences in the population size may occur for urban
and rural areas)
‰
To be consistent (to a larger extent) with EA boundaries
used in the previous census
‰
To be large enough to guarantee data privacy
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
3. Main critical criterion to delineate EA boundaries
‰
The main critical criterion is to estimate the
approximately equal population size of EAs
‰
The three methods are:
- Acquisition of administrative records (or by other
sources of information)
- Fieldwork activities (dwellings count)
- Through remotely sensed data (satellite imagery and
aerial photographs), and GPS receivers
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
4. Principal type of maps for census operations
‰ Small scale maps
‰ Topographic maps
‰ City maps
‰ Sketch maps
‰ High-resolution satellite images and aerial photos
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
4. Small scale map
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
4. Topographic map
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
4. City map
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
4. Sketch map
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
4. Manual EA delineation
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
4. High-resolution satellite imagery
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
4. Aerial photograph
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
5. Satellite remote sensing
‰
The spatial resolution of a satellite image is measured by
the size of a pixel on the ground. The size for commercial
satellites varies from the sub-one-meter of the most
popular high-resolution systems such as Quickbird and
Ikonos
‰
Indian Remote Sensing (IRS), SPOT’s panchromatic
sensor and Landsat multi-spectral imagery are also
considered high resolution systems which allow mapping
at cartographic scales of 1:25,000 to 1:50,000 or smaller
‰
In September 2008, the remote sensing company GeoEye
launched a sensor with a pixel size of 0.41 meters
panchromatic and 1.65-meter multispectral
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
5. Satellite remote sensing (cont.)
‰
Only some remotely sensed data products serve census
work well, namely high spatial resolution data such as
Geoeye (0.41), Quickbird (0.82m), Ikonos (1m), IRS
(5.8m pan), Orbimage 3 and 4 (1m), and SPOT 5 (2.5m).
Ikonos was launched in 1999 and Quickbird was
launched in 2001.
‰
For most census applications, 5m or better spatial
resolution is needed to identify housing units. Landsat
may be considered in some cases only in rural areas
‰
On line remotely sensed data such as Google Earth,
GlobeXplorer, ArcGIS Explorer, and Microsoft Virtual
Earth can be used as a first test, but the image quality
may not be suitable for detailed EA mapping
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
5. Satellite remote sensing (cont.)
‰
High resolution satellite images show a level of
geographic detail that is almost comparable to digital
orthophoto maps created from air photos.
‰
Cloud free high-resolution images may allow counts of
single housing units
‰
Aerial photography is often done on ad hoc basis, and
may be more suitable for detailed surveying and
mapping projects. New digital aerial photography may
offer superior image quality over even high-resolution
satellite imagery
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
5. Satellite remote sensing (cont.)
Main advantages and disadvantages of high-resolution
remotely sensed data:
‰
Advantages:
- High spatial resolution images offer the ability to cover
large areas at a level of detail sufficient for EA
delineation, provided population estimates exist for the
areas delineated
- Imagery can permit mapping of inaccessible areas
- Usually there are no restrictions for their acquisition
‰
Disadvantages:
- Cloud may cover restricts image interpretation
- Positional accuracy may be low without accurate orthorectification process
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
6. Aerial photography
‰
Aerial photography is obtained using specialized cameras
on-board low flying planes. The camera captures the
image on photographic film, or digitally
‰
Traditionally, the end products of an aerial photography
project are printed photos of an area on the ground. The
photogrammetrist can combine these photos to produce
a seamless mosaic covering very large part of a territory
‰
Nowadays, the most common approach is to convert the
photo negative directly into a film transparency which is
scanned using a very high resolution scanning device.
The result is a digital image that can be displayed and
processed further on a computer
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
6. Aerial photography (cont.)
‰
Additional processing is required to produce orthophoto
maps which combine the geometrical accuracy of a
topographic map with the large detail of a photograph
‰
The construction of digital orthophotos requires
considerable expertise in photogrammetric methods,
which is not usually present in a census organization
‰
The census organization therefore needs to establish a
collaborative agreement with the National Mapping
Agency
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
6. Aerial photography (cont.)
‰
Orthophoto maps may also support dwelling unit counts
and population estimation, if is available a reliable
estimate of the average number of persons per
household
‰
In a rural setting, the number of dwelling units can be
determined fairly easily, while in urban settings, the
number of dwellings may be more difficult to determine
‰
Since the orthophotos are correctly georeferenced, the
resulting enumeration areas will also be registered in a
proper map projection with known parameters
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
6. Aerial photography (cont.)
Main advantages and disadvantages of high-resolution
remotely sensed data:
‰
Advantages:
- Air photos provide a large amount of detail and can be
interpreted visually
- They usually cover the entire country
‰
Disadvantages:
- Aerial photo processing requires expensive equipment
and specialized expertise
- Their production is in general more expensive in
comparison with high-resolution satellite imageries and
requires Governmental approval
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
Aerial photograph
(Resolution 25 cm)
Ikonos satellite imagery
(Resolution 1 m)
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
7. Global Positioning System (GPS)
‰
Determine current position based on signals sent by a
number of satellites
‰
GPS receivers collect the signals transmitted from more
than 24 satellites—21 active satellites and three spares.
The system is called NAVSTAR, and is maintained by the
U.S. Department of Defense
‰
In each area of the world, five to eight GPS satellites are
within the “field of view” of a user on the earth’s surface
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
7. Global Positioning System (cont.)
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
7. Global Positioning System (cont.)
GPS uses satellite signals to obtain latitude/longitude coordinate
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
7. Global Positioning System (cont.)
‰
The accuracy of inexpensive GPS receivers is normally
around 10-20 meters for civilian applications. Altitude
information is less reliable than latitude and longitude
‰
To obtain more accurate positions GPS readings have to
be longer
‰
To improve accuracy, differential GPS (DGPS) system
(and real time system) use correction information
transmitted from a permanent base station with
precisely known coordinates to correct the satellite
signals (1-2 meters with non-geodetic receivers)
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
7. Global Positioning System (cont.)
‰
‰
Other global satellite navigation systems are:
- GLONASS, operated by the Ministry of Defense of the
Russian Federation
‰
- Galileo, the European system which will probably starts
operations in 2013
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
7. Global Positioning System (cont.)
‰
GPS in mapping activities:
- support for the preparation of enumerator maps for
census activities
- Coordinates can be downloaded or entered manually
into a GIS or other digital mapping system, where they
can be combined with other georeferenced information
- support for the delineation of of the administrative
boundaries
- locating housing units
- creation of the street network
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
7. Global Positioning System (cont.)
‰
Use of GPS for georeferencing and orthorectification of
remotely sensed data
Example of Ikonos satellite image with GCPs for
orthorectification
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
6. Global Positioning System (cont.)
‰
‰
‰
‰
‰
‰
Advantages:
- Fairly inexpensive, easy-to-use
- Sufficient accuracy for many census mapping applications—
high accuracy achievable with differential correction
- Collected data can be read directly into GIS databases
making intermediate data entry or data
Disadvantages:
- Signal may be obstructed in dense urban or wooded areas
- Standard GPS accuracy may be insufficient in urban areas
making differential techniques necessary
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
8. Some conclusions
‰
High-resolution satellite imagery and aerial photographs
may be used generally to estimate small area population size
and for delineation of EAs in rural environment (where
buildings are in general scattered, and with one or two
storey)
‰
In urban areas, fieldwork activities for dwellings count
seems not always possible to be avoided for a reliable
delineation of EAs
‰
In this respect, the use of GPS may support considerably
fieldwork activities, if the base map (Satellite imagery, aerial
photo or other digital cartography) is accurately
georeferenced and orthorectified
‰
In general, the most suitable strategy seems to be the
“change-detection approach”, by investigating in the field
only areas with important changes, detected in office trough
the analysis of remote sensed data
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008
Interuniversity Research Center for Sustainable Development
Sapienza University of Rome, Italy
THANK YOU
2010 WORLD POPULATION AND HOUSING CENSUS PROGRAMME
Regional Workshop on International Standards, Contemporary Technologies for Census
Mapping and Data Processing, Minsk, Belarus, 8-12 December 2008