Another applicable remote-sensing technique, with resolution on the order of 1 m,
is interferometric SAR (inSAR). This technology has been used for flood risk mapping
in the United Kingdom (Galy and Sanders, 2002). A complete review of LIDAR,
photogrammetry, inSAR and other technologies used in the production of digital
elevation models (DEMs) is provided by Maune (2001).
1.3 CASE STUDY: FLOOD RISK MAPPING IN PRINCE EDWARD ISLAND,
CANADA
Storm-surge flood risk mapping was one of the major objectives of a recent project
(McCulloch et al., 2002) to evaluate coastal impacts of climate change and sea-level
rise on Prince Edward Island in southeastern Canada (Figure 1). Airborne LIDAR
surveys were employed in this project and the resulting data sets provided the essential
foundation for flood risk mapping in the urban centre of Charlottetown and in a
representative rural area in the vicinity of North Rustico (Webster et al., 2002). It was
recognized at the outset that a high-resolution representation of the coastal topography
would be essential for predicting areas at risk of storm-surge flooding (Webster et al.,
2001, 2003). A multi-disciplinary scientific team was involved in this project and
contributed related analyses of sea-level change, storm-surge climatology, wave and
sea-ice climatology, statistics of flood probability, coastal erosion, socio-economic
impacts, and adaptation options (Chagnon, 2002; Forbes and Manson, 2002; Forbes
et al., 2002; Manson et al., 2002; Milloy and MacDonald, 2002; Parkes and Ketch, 2002;
Parkes et al., 2002; Thompson et al., 2002). The City of Charlottetown Planning
Department also participated in the project and incorporated the results into their
information system. The data have wide applicability, beyond climate-change impacts
assessment, among other fields, including geological and ecological research, urban and
regional planning, coastal management, and agriculture. The remainder of this chapter
describes the flood risk mapping component of this project utilizing LIDAR for coastal
areas on Prince Edward Island.
1.3.1 LIDAR mapping
LIDAR mapping involves an aircraft emitting laser pulses toward the ground and
measuring the return time of the pulse (see Webster et al., 2004). The laser scan is
acquired by rapid repetition of the laser pulse transmitter and cross-track deflection of
the beam using an oscillating mirror to produce a zigzag pattern of laser hits on exposed
surfaces below the aircraft (Figure 2). A Time Interval Meter (TIM) records the mirror
scan angle, the time when the pulse is transmitted from the sensor, the time of the
returning reflected pulse, and in some cases the intensity of the return. The
configuration of the TIM is what determines if the sensor captures the first or last
reflected returns. New generation LIDARs are capable of capturing first, last, and
intermediate returns, along with multiple intensities. The data volume with such sensors
is a potential problem and the information content of the intermediate returns is an area
of active research. Using precise differential Global Positioning System (GPS)
technology to determine the location of the aircraft (Krabill and Martin, 1987) and an
Inertial Measurement Unit (IMU) to measure the aircraft attitude (pitch, yaw, and roll),
the location of individual laser returns measured by the TIM can be determined (Figure 2).
159
Airborne Laser Altimetry
is interferometric SAR (inSAR). This technology has been used for flood risk mapping
in the United Kingdom (Galy and Sanders, 2002). A complete review of LIDAR,
photogrammetry, inSAR and other technologies used in the production of digital
elevation models (DEMs) is provided by Maune (2001).
1.3 CASE STUDY: FLOOD RISK MAPPING IN PRINCE EDWARD ISLAND,
CANADA
Storm-surge flood risk mapping was one of the major objectives of a recent project
(McCulloch et al., 2002) to evaluate coastal impacts of climate change and sea-level
rise on Prince Edward Island in southeastern Canada (Figure 1). Airborne LIDAR
surveys were employed in this project and the resulting data sets provided the essential
foundation for flood risk mapping in the urban centre of Charlottetown and in a
representative rural area in the vicinity of North Rustico (Webster et al., 2002). It was
recognized at the outset that a high-resolution representation of the coastal topography
would be essential for predicting areas at risk of storm-surge flooding (Webster et al.,
2001, 2003). A multi-disciplinary scientific team was involved in this project and
contributed related analyses of sea-level change, storm-surge climatology, wave and
sea-ice climatology, statistics of flood probability, coastal erosion, socio-economic
impacts, and adaptation options (Chagnon, 2002; Forbes and Manson, 2002; Forbes
et al., 2002; Manson et al., 2002; Milloy and MacDonald, 2002; Parkes and Ketch, 2002;
Parkes et al., 2002; Thompson et al., 2002). The City of Charlottetown Planning
Department also participated in the project and incorporated the results into their
information system. The data have wide applicability, beyond climate-change impacts
assessment, among other fields, including geological and ecological research, urban and
regional planning, coastal management, and agriculture. The remainder of this chapter
describes the flood risk mapping component of this project utilizing LIDAR for coastal
areas on Prince Edward Island.
1.3.1 LIDAR mapping
LIDAR mapping involves an aircraft emitting laser pulses toward the ground and
measuring the return time of the pulse (see Webster et al., 2004). The laser scan is
acquired by rapid repetition of the laser pulse transmitter and cross-track deflection of
the beam using an oscillating mirror to produce a zigzag pattern of laser hits on exposed
surfaces below the aircraft (Figure 2). A Time Interval Meter (TIM) records the mirror
scan angle, the time when the pulse is transmitted from the sensor, the time of the
returning reflected pulse, and in some cases the intensity of the return. The
configuration of the TIM is what determines if the sensor captures the first or last
reflected returns. New generation LIDARs are capable of capturing first, last, and
intermediate returns, along with multiple intensities. The data volume with such sensors
is a potential problem and the information content of the intermediate returns is an area
of active research. Using precise differential Global Positioning System (GPS)
technology to determine the location of the aircraft (Krabill and Martin, 1987) and an
Inertial Measurement Unit (IMU) to measure the aircraft attitude (pitch, yaw, and roll),
the location of individual laser returns measured by the TIM can be determined (Figure 2).
159
Airborne Laser Altimetry