basic concepts and challenges of remote sensing - elib.dlr.de · definition: remote sensing is the...

IGSSE Forum Raitenhaslach, 26 June 2013

Basic concepts and challenges of remote sensing

Peter Gege

DLR, Earth Observation Center, Institut für Methodik der Fernerkundung, Oberpfaffenhofen, 82234 Wessling

with contributions from

Richard Bamler, Michael Eineder

Definition: Remote sensing is the acquisition of information about an object or phenomenon without making physical contact with the object. In modern usage, the term generally refers to the use of aerial or satellite sensor technologies to detect and classify objects on Earth (in the atmosphere, on the surface, in water).

www.DLR.de • Chart 2 > Remote Sensing > P. Gege > 26.6.2013

Sputnik 1

Remote sensor

What is Remote Sensing?

www.DLR.de • Chart 3

Remote sensing of most atmospheric components makes use of their absorption properties. Remote sensing of the Earth surface from satellite is restricted to the atmospheric windows.

Useful Wavelengths

Paul R. Baumann (2010). http://www.oneonta.edu/faculty/baumanpr/geosat2/RS-Introduction/RS-Introduction.html

> Remote Sensing > P. Gege > 26.6.2013

Bands

K X C S L P



1418 1419 1420 1421 1422

0.0

0.2

0.4

0.6

0.8

1.0

Tran

smitt

ance

Wavenumber/cm-1

Column density/cm-2

#22 1.93x1017

#23 1.09x1018

#24 4.62x1018

#25 1.03x1019

#26 3.89x1019

#27 1.28x1020

#28 2.56x1020

FT spectrometer at DLR

Useful Wavelengths H20

Atmospheric components Remote sensing requires detailed knowledge of optical properties



Example: Microwave Humidity Sounder (MHS) on MetOp-A

Derives a 3D picture of atmospheric humidity (5 channels ↔ 5 altitudes)

Data acquired over one complete satellite orbit Channel 1 (89 GHz = 3 mm)

Water vapour concentration


O3 tot.

NO2 tot.

NO2 trop.

SO2

HCHO

BrO

H2O

Clouds

2007

-

201

2

Products 24/7

2h NRT

Example: Global Ozone Monitoring Experiment-2 (GOME-2) on MetOp-A

Long-term monitoring of atmospheric trace gas constituents


7

1970-1979 1980-1989 1990-1999 2000-2009 2040-2049

…

Mod

el

Sate

llite

Example: Monitoring and Prediction of the Ozone Layer



Useful Wavelengths


Bands

K X C S L P

Earth surface Remote sensing can utilize the atmospheric windows Information is derived from geometry, surface structure, spectral properties, penetration depth


Example: Digital Elevation Model from Stereo Images

3D model of London derived from 5 viewing angles

> Remote Sensing > P. Gege > 26.6.2013 www.DLR.de • Chart 9

Example: Bathymetry from Ocean Wave Patterns

Water depth near coastline, used e.g. to predict tsunami propagation


http://en.wikipedia.org/wiki/File:TerraSARX_Logo.png

Example: Biological Parameters from Spectral Properties

Temporal development of plant productivity



Useful Wavelengths



Water constituents Water is transparent only in the visible and near UV

Example: Chlorophyll and Suspended Matter

Results of an airborne campaign in Lake Constance (Bodensee)


Chlorophyll (µg/l) Suspended matter (mg/l)

T. Heege (2000): Flugzeuggestützte Fernerkundung von Wasserinhaltsstoffen am Bodensee. Dissertation. DLR-Forschungsbericht 2000-40, 141 Seiten

T. Heege, J. Fischer (2004): Mapping of water constituents in Lake Constance using multispectral airborne scanner data. Can. J. Remote Sensing, Vol. 30, No. 1, pp. 77–86

Uncertainty: ± 20 % Uncertainty: ± 17 %


C. Häse, T. Heege (2003): A remote sensing algorithm for primary production in Lake Constance with special emphasis on the integration level. ENVOC Final Report, March 2003. T. Heege et al. (2003): Airborne multi-spectral sensing in Shallow and Deep waters. Backscatter Vol. 14, No.1, 17-19.

Result based upon • P-I-curves from 15 years • Chlorophyll • Attenuation (from Chl, Y, SPM) • PAR

mgC m-2 h-1 60 80 100 120 140

Example: Primary productivity

Results of an airborne campaign at Lake Constance (Bodensee)

Passive Sensors Passive sensors detect natural radiation that is emitted or reflected by the object or surrounding areas. Examples: CCD cameras, infrared sensors, imaging spectrometers.


Active Sensors The sensor emits radiation which is directed toward the target to be investigated. The radiation reflected from that target is detected and measured by the sensor. Examples: RADAR, LIDAR.

Sensor Types


Example for passive sensors: Hyperspectral Sensors

Imaging spectrometers allow spectroscopy by remote sensing

Whiskbroom Scanner Simultaneously recorded: N channels = 1 spectrum

Pushbroom Scanner Simultaneously recorded: N channels x M pixels = M spectra of 1 image line

Airborne sensor ROSIS

Airborne sensor HySpex


Atmosphere corrected with ATCOR-4 Inverse modeling with WASI-2D

Water depth (m) CDOM concentration Absorption at 440 nm(1/m)

Sunglint (1/sr)

Typical spectrum of a single pixel

CDOM type Spectral slope (1/nm)

Example for Hyperspectral Applications

Remote sensing of shallow water areas


Example for active sensors: TerraSAR-X and Tandem-L www.DLR.de • Chart 18 > Remote Sensing > P. Gege > 26.6.2013

Digital elevation model (Alaska)

Ice Thickness Changes from 2000 to 2011 South Patagonia Ice Field DEM difference: TanDEM-X (2011) – SRTM (2000)

N

+100

-100

0

elevation change [m]


Subsidence in Venice www.DLR.de • Chart 21 > Remote Sensing > P. Gege > 26.6.2013


Sensor development Sensor launch Sensor calibration Georeferencing Atmosphere correction Determination of optical properties Model development Inversion Validation ...

Challenges of Remote Sensing ... all this must be done properly to get the shown nice results


Modern Sysiphus by Dluho. toonpool.com

Develop sensors to answer specific questions Exploit information content of data sets

Models “It is the theory that decides what can be observed.” (A. Einstein)


Concept of Remote Sensing


Applications

Technology

Models


Concept of Remote Sensing ... and of much more, maybe also of Shaping interdisciplinary processes?


Applications

Technology Thank you for your attention!

M. C. Escher: Ascending and Descending

basic concepts and challenges of remote sensing - elib.dlr.de · definition: remote sensing is the...

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