Transcript Disaster Geo-Information Management – Maximizing Data Accuracy Speaker : Sr. Mohaizi Mohamad, FISM, FMGA PhD Mgmt, MSc LAD (Mal), MSc GIS (Aust), MSc Cart(Neth), BSc.

Disaster Geo-Information
Management – Maximizing
Data Accuracy
Speaker :
Sr. Mohaizi Mohamad, FISM, FMGA
PhD Mgmt, MSc LAD (Mal), MSc GIS (Aust), MSc Cart(Neth), BSc Survey (Mal)
Email: [email protected]
Hp: +6019-6264421
Outline Presentation
•
•
•
•
•
•
•
•
•
•
Abstract
Introduction
Methodology
LiDAR Work
Accurate Data For Flood
LiDAR Water Flow
LiDAR Drainage Pattern
Optimum Data Accuracy
Ground Registration
Conclusion
2
Abstract
• Flood occurrence increased alarmingly in recent years in Northern
Peninsular Malaysia.
• Largely caused by human activities,
• continued development of the densely populated flood plains,
• encroachment on flood-prone areas and
• destruction of forest and hill slopes.
• Official solutions for flood control - engineering based, ineffective
to combat extensive monsoon floods.
• Readiness of highly accurate topographic heighting data at 10cm is
recommended for hydrological spatial analysis.
• LIDAR technology couple with GPS technology of First Order
Geodetic needed to create a highly precise GIS-based topographic
layer for automated hydrological systems analyses and automated
flood plan delineation.
3
Flood Kedah, Nov 2010
Source: Google
• Using LIDAR technology
couples with GPS
technology of First
Order Geodetic and
methodologies, an
accurate and reliable
Flood Risk Map can
easily be produced over
Northern Peninsular
Malaysia for Disaster
Geo-Information
Management.
4
Introduction
• LiDAR stand for Light Detection And Ranging.
• An optical remote sensing technology that measures
properties of scattered light to find range and/or other
information of a distant target
.
• The prevalent method to determine distance to an object
or surface is to use laser (light) pulses. Like the similar
radar technology, which uses radio waves, the range to
an object is determined by measuring the time delay
between transmission of a pulse and detection of the
reflected signal.
• LIDAR technology has application in Geomatics,
archaeology, geography, geology, geomorphology,
seismology, remote sensing and atmospheric physics.
5
Methodology
LIDAR system
consists of
several
advanced
technologies as
can be seen in
the image.
6
LiDAR Work
•
•
•
•
Infrared Laser scans from side to side
Receiver – measure accurately intensity, travel time &
compute distance of the first pulse and the last returned
pulses.
IMU- keep track of the rotation of the aircraft in three axis
GPS- keep track of the exact location of the aircraft in space
7
Accurate Data For Flood
MADA, Kedah, Malaysia; Feb. 2010
• LIDAR data is very high vertical accuracy which enables it to represent
the Earth surface accurately.
• Laser returns are recorded from no matter what target the laser
happens to strike.
• Red points indicated as the ground points, extracted from the overall
LIDAR measurements.
• White points classified as the trees or non-ground point heights.
• Classification of these two types of points will represent the different
data for bare earth and features with accurate elevation value.
8
Classification LiDAR Data
Points of vegetation
Points of soil
MADA, Kedah, Malaysia; Feb. 2010
9
9
LiDAR Water Flow
• Rapid LiDAR data with the accuracy of 10cm on open area and
1m on heavily vegetated area (theoretically), LIDAR data are
capable of creating accurate models for drainage flow pattern
modeling to analyze the flood.
MADA, Kedah, Malaysia; Feb. 2010
White lines and arrows - directions of waterflow if water falls on every
position. The thickness if the line represent the speed of waterflow.
10
LiDAR Drainage Pattern
• The sump points are vital for flood risk detection, flood preventing,
and area effected by flood analysis.
• With additional data such as soil information, these sump points can
be shown as the precise positions of the risky water sump that may
cause landslide after the flood season.
MADA, Kedah, Malaysia; Feb. 2010
Green and Red rectangular represent the waterflow directions and the
water sump points
11
Optimum Data Accuracy
MADA, Kedah, Malaysia; July 2010
MADA, Kedah, Malaysia; July 2010
• By using RTK GPS, rapid ground
data will collect at designated
area and will compare with LIDAR
data.
• This technique ensures that all
LiDAR data achieve the accuracy
which is up to 5cm on the clear
ground.
• By using RTK technique, the LiDAR
data will reduce to the exact level
of elevation based on the ground
survey information.
• In Malaysia, the RTK GPS
technique is being governed by
the MyRTKNet and MyGeoid by
JUPEM.
12
Ground Registration
MADA, Kedah, Malaysia; July 2010
• Rapid GPS ground control will be compared with LiDAR data to identify the different
heighting value.
• The average of different heighting value will be used to reduce all the heighting of
LiDAR data. The deliverable is the + 5cm accuracy achievement.
13
Analysis Data
POINT ID
X
Y
Z GCPs (m)
Z LiDAR (m)
Different
Value (m)
1
251291.5427
706061.3381
4.3868
4.510
0.1232
2
251309.2661
706037.8725
4.5067
4.590
0.0833
3
251325.1292
706021.8001
4.4007
4.390
0.0107
4
251297.3525
706002.1293
4.6168
4.600
0.0168
5
251279.2489
706029.9268
4.5253
4.580
0.0547
6
251269.2431
706047.8952
4.4442
4.280
0.1642
7
251243.2594
706024.8210
4.4751
4.510
0.0349
8
251263.0533,
706003.7961
4.6441
4.660
0.0159
9
251277.2689
705985.7231
4.5201
4.570
0.0499
10
250865.0077
706105.6406
4.5781
4.540
0.0381
11
250873.7549
706094.7060
4.4868
4.500
0.0132
12
250858.6140
706080.0587
4.4244
4.410
0.0144
13
250849.2627
706091.9289
4.5229
4.510
0.0129
14
250839.2160
706102.1302
4.4874
4.460
0.0274
Average
Different (m)
0.047114
• The Average Different heighting value will insert into modeler to reduced all LiDAR data
over designated area to achieve the optimum data accuracy.
14
RTK GPS
• Real time kinematic (RTK) surveying is the latest dynamic GPS
survey technique that utilizes short observations times and enable
you to move between stations.
• RTK GPS can instantly determine the position of a roving unit to
centimeter-level accuracy using carrier phase positioning.
• This technique is ideal for various applications such as engineering,
cadastral, topographic and detail surveys.
• The use of a network of reference stations instead of a single
reference station allows to model the systematic errors in the
region and thus provides the possibility of an error reduction.
• This allows a user not only to increase the distance at which the
rover receiver is located from the reference, it also increases the
reliability of the system and reduces the RTK initialization time.
15
MyRTKnet Configuration
• Network of 50 dual frequency GNSS referense stations in
Peninsular Malaysia
• Network of 28 dual frequency GNSS reference stations in
East Malaysia
• Control Centre at JUPEM Headquarter
16
RTK VRS Networking
• This latest technique significantly reduces systematic errors
and extends the operating range with improved initialization
and accuracy. It is an autonomous surveying where users do
not need to set up their own base stations.
• This technique provides integrity monitoring with all users
sharing the same common established coordinate frame.
17
Conclusion
• Airborne LIDAR technology together with GPS survey is now a
proven method for acquiring accurate digital terrain model data
and associated imagery under a wide range of conditions.
• As an active sensor it can be used when other remote sensing
tools will not work, especially in the coastal zone where its
flexibility and non invasiveness are extremely relevant features.
• We believe that access to a technology that enables the
acquisition and fusion of baseline cartographic data and digital
photos in much shorter time periods when compared to
conventional methods can speed up the initiation of projects
related to flood analysis, and we believe GPS survey will can
optimum the accuracy of LIDAR data to ensure it will be a very
promising technique in topographic surveying.
18