Post on 24-Jul-2018
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 1 of 13Remote Sensing - Overview
Remote Sensing and Lidar: (Section 27.19-27.20) We have spent some time to understand
photogrammery and how to derive elevation data from it. However, there are limitations are limitations
to the measurement of parallax that relate to features that can be extracted from air photo and the
scale of the airphoto. Other means of determining elevation data have been determined though
LIDAR measurements and through radar remote sensing.
LIDAR: (Section 27.19) A play on the acronym RADAR (RADio Detection And Ranging), LIDAR (LIght
Detection and Ranging) combines: i) aircraft overflights, ii) relative GPS positioning, iii) inertial
navigation and iv) laser range finding to map ground targets to a very high accuracy. The GPS unit
determines the location of the aircraft (X,Y,Z), while the internal measures determine the rotation of the
aircraft (pitch, roll and yaw). The laser scanner can then determine the distance to ground targets and
because of the high sampling rate and narrow beam can penetrate tree cover to determine ground
elevation.
LIDAR SystemLIDAR Image of Ground Zero NYC Septemer 17, 2001
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 2 of 13Remote Sensing - Overview
LIDAR Digital Elevation Model (DEM)
Airborne Radar Digital Elevation Model (DEM)
LIDAR system is better able to penetrate
the tree canopy to extract surface
elevation data. Road network and
stream channels are visible.
Airborne RADAR system captures the
gross features of elevation but is not
able to extract finer features. This is due
to wider beam width and lower look
angles with radar that prevents canopy
penetration.
http://www.cfr.washington.edu/research.pfc/research/jfsp/index.htm
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 3 of 13Remote Sensing - Overview
Stephenville Flooding - 2005
How would you predict this event?
Land Cover Data
LandSat7
Digital Terrain Data
Shuttle Radar Topographic Mission
(SRTM)
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 4 of 13Remote Sensing - Overview
LandSat 7 & SRMT View of Stephenville Google Earth View of Stephenville(LandSat foreground; Quickbird background)
Close-Up (next page)
Shuttle Radar Topographic Mission (SRTM) DEM provides 100m x 100m elevation
data over most of the globe (60N to 55S).
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 5 of 13Remote Sensing - Overview
Close up view of the Stephenville area
shows that the high resolution
Quickbird imagery (0.7m x 0.7m) does
not match with the coarse resolution
SRTM DEM (100m x100m).
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 6 of 13Remote Sensing - Overview
What is Remote Sensing?
Remote Sensing Process: (A) An energy source emits radiation, (B) this interacts with the
atmosphere, and (C) the target. The result is (D) recorded by a sensor, and (E) transmitted for (F)
processing and (G) application.
"Remote sensing is the science (and to some extent,
art) of acquiring information about the Earth's surface
without actually being in contact with it. This is done
by sensing and recording reflected or emitted energy
and processing, analyzing, and applying that
information."
From: http://ccrs.nrcan.gc.ca/resource/tutor/fundam/index_e.php
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 7 of 13Remote Sensing - Overview
Satellite Orbits
Polar Orbit
Eg: Landsat
Geostationary Orbit
eg: GOES
Landsat ETM+
Sun Synchronous (10 am local) Polar Orbit
Altitude: 705 km
Repeat Cycle: 16 days (233 orbits)
Resolution: 30m x 30m
GOES -8
Geostationary Orbit
Altitude: 36,000 km
Repeat Cycle: Continuous
Resolution: 4km x 4km
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 8 of 13Remote Sensing - Overview
Electromagnetic Radiation
Most remote sensing information is received in the
form of electromagnetic radiation. This radiation
travels at the speed of light (c) and two important
characteristics of this radiation are frequency (f) andits wavelength ( ). These are related by:
c = f
where: c = speed of light 3x108 m/s
f = frequency (Hz = cycles per sec)
= wavelength (m)
0.4 μm 0.7 μmLandSat
(7 channels)
RadarSat
(1 channel)
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 9 of 13Remote Sensing - Overview
Active Radar Satellites - Unlike LandSat which reflects reflected solar energy from
the earth’s surface, radar satellites emit there own energy and then detect the
reflections. RadarSat is the only Canadian remote sensing satellite.
RADARSAT 1 - C-Band Radar (5.3 GHz / 5.7 cm)
Altitude - 800 km
Internal Energy Source
Resolution - 9 m (Fine Beam)
100 m (SCANSAT)
Polar Orbit
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 10 of 13Remote Sensing - Overview
Winnipeg 1997
“Flood of the Century”
RADARSAT 1 - Active RadarCoverage day or night, rain or shine
Radar Remote Sensing Uses - Flooded area determination; radar
signals are absorbed by water which provides a contrast against
the land. It is also not affected by clouds and can operate day or
night since it is an “active” system.
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 11 of 13Remote Sensing - Overview
Water is a polar molecule
Radar beams induce vibration
Vibration Resistance
(Di-Electric) increases in ice
and dry soil Wet Snow - Dark
Dry Snow and Urban - Light
RADARSAT - Ottawa
Radar Remote Sensing can “see” things that human senses cannot such as the properties of water.
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 12 of 13Remote Sensing - Overview
Shuttle Radar Topographic Mission (SRTM)
195 ft
Data Resolution (1 m elevation)
USA: 1 arc sec (~30 m)
60N-60S: 3 arc sec (~100 m)
Generated Based on Stereoscopy
ENGI 3703Surveying and Geomatics
TopicInstructor: Prof. Ken Snelgrove
Lect 24 - Nov 21/07 Slide 13 of 13Remote Sensing - Overview
Google Earth Tour
-various image resolutions: LandSat (15m) from Terrametrics
Quickbird (0.7 m) from DigitalGlobe
High Resolution Air Photos (0.03 m) (Google Campus)
Special Projects (National Geographic)
-New high resolution DEM (10m x10m): Switzerland.