Digital Image Processing: A Remote Sensing Digital Image Processing: A Remote Sensing PerspectivePerspectivePerspectivePerspectiveLecture 1Lecture 1

ASPRSASPRS adoptedadopted aa combinedcombined formalformal definitiondefinition ofofphotogrammetryphotogrammetry andand remoteremote sensingsensing asas (Colwell,(Colwell,19971997))::19971997))::

the art, science, and technology of the art, science, and technology of obtaining reliable information about physicalobtaining reliable information about physicalobtaining reliable information about physical obtaining reliable information about physical objects and the environment, through the objects and the environment, through the process of recording, measuring and process of recording, measuring and interpreting imagery and digital interpreting imagery and digital representations of energy patterns derived representations of energy patterns derived f t t t f t t t from noncontact sensor systems.from noncontact sensor systems.

A remote sensing instrument gcollects information about an object or phenomenon within the instantaneous field of viewthe instantaneous-field-of-view (IFOV) of the sensor system without being in direct physical contact with it. The sensor is located on a suborbitalor satellite platform.p

IsIs RemoteRemote SensingSensing aa Science?Science?A A sciencescience is defined as the broad field of human is defined as the broad field of human knowledge concerned with facts held together by knowledge concerned with facts held together by principlesprinciples (rules)(rules)principlesprinciples (rules).(rules).

Scientists discover and test facts and principles by the Scientists discover and test facts and principles by the scientific method, an orderly system of solving problems. scientific method, an orderly system of solving problems. Scientists generally feel that any subject that humans can Scientists generally feel that any subject that humans can study by using the scientific method and other special study by using the scientific method and other special y y g py y g prules of thinking may be called a science.rules of thinking may be called a science.

The sciences include 1)The sciences include 1) mathematicsmathematics andand logiclogic 2) the2) theThe sciences include 1) The sciences include 1) mathematics mathematics andand logiclogic, 2) the , 2) the physical sciencesphysical sciences, such as physics and chemistry, 3) the , such as physics and chemistry, 3) the biological sciencesbiological sciences, such as botany and zoology, and 4) , such as botany and zoology, and 4) the the social sciencessocial sciences, such as geography, sociology, and , such as geography, sociology, and anthropology.anthropology.

Remote sensing is a tool or technique similar toRemote sensing is a tool or technique similar toRemote sensing is a tool or technique similar to Remote sensing is a tool or technique similar to mathematics. Using sensors to measure the amount of mathematics. Using sensors to measure the amount of electromagnetic radiation (EMR) exiting an object or electromagnetic radiation (EMR) exiting an object or

hi f di t d th t tihi f di t d th t tigeographic area from a distance and then extracting geographic area from a distance and then extracting valuable information from the data using mathematically valuable information from the data using mathematically and statistically based algorithms is a and statistically based algorithms is a scientificscientific activity.activity.

It functions in harmony with other It functions in harmony with other spatialspatial datadata--collection collection yy pptechniques or tools of the techniques or tools of the mapping sciencesmapping sciences, including , including cartography and geographic information systems (GIS) cartography and geographic information systems (GIS) (Clarke 2001)(Clarke 2001)(Clarke, 2001). (Clarke, 2001).

InformationInformation aboutabout anan ObjectObject oror AreaArea

S bt i ifi i f ti b t bj t (S bt i ifi i f ti b t bj t (Sensors obtain specific information about an object (e.g., Sensors obtain specific information about an object (e.g., the type or classification of the the type or classification of the wetalndwetalnd ) or the geographic ) or the geographic extent of a phenomenon (e.g., the uplandextent of a phenomenon (e.g., the upland-- wetland wetland p ( g , pp ( g , pboundaryboundary

The EMR reflected, The EMR reflected, ,,emitted, or backemitted, or back--scattered from an scattered from an object or geographicobject or geographicobject or geographic object or geographic area is used as a area is used as a surrogatesurrogate for the for the actual property actual property under investigation.under investigation.

USFWS photo

R t i iR t i i bt ibt i if thif th i li l

Advantages of Remote SensingAdvantages of Remote SensingRemote sensing is Remote sensing is unobtrusiveunobtrusive if the sensor if the sensor passivelypassivelyrecords the EMR reflected or emitted by the object of records the EMR reflected or emitted by the object of interest. Passive remote sensing does not disturb the interest. Passive remote sensing does not disturb the ggobject or area of interest. object or area of interest.

Remote sensing devices may be programmed to collect Remote sensing devices may be programmed to collect data systematically, such as within a 9 data systematically, such as within a 9 9 in. frame of 9 in. frame of vertical aerial photography. This systematic data collection vertical aerial photography. This systematic data collection can remove the sampling bias introduced in some can remove the sampling bias introduced in some in situin situp gp ginvestigations. investigations.

Under controlled conditions, remote sensing can provide Under controlled conditions, remote sensing can provide fundamental biophysical information, including fundamental biophysical information, including x,yx,ylocation,location, zz elevation or depth, biomass, temperature, and elevation or depth, biomass, temperature, and moisture content. moisture content. What and WhereWhat and Whereo s u e co eo s u e co e at a d e eat a d e e

Limitations of Remote SensingLimitations of Remote Sensing

The greatest limitation is that it is often The greatest limitation is that it is often oversoldoversold. . Remote Remote sensing is not a panaceasensing is not a panacea that provides all the information that provides all the information

d d t d t h i l bi l i l i l id d t d t h i l bi l i l i l ineeded to conduct physical, biological, or social science needed to conduct physical, biological, or social science research. It provides some spatial, spectral, and temporal research. It provides some spatial, spectral, and temporal informationinformation of value in a manner that we hope is efficient of value in a manner that we hope is efficient and economical.and economical.

Human beingsHuman beings select the appropriate remote sensing select the appropriate remote sensing t t ll t th d t if th i l tit t ll t th d t if th i l tisystem to collect the data, specify the various resolutions system to collect the data, specify the various resolutions

of the remote sensor data, calibrate the sensor, select the of the remote sensor data, calibrate the sensor, select the platform that will carry the sensor, determine when the platform that will carry the sensor, determine when the p yp ydata will be collected, and specify how the data are data will be collected, and specify how the data are processed. Human methodprocessed. Human method--produced error may be produced error may be introduced as the remote sensing instrument and missionintroduced as the remote sensing instrument and missionintroduced as the remote sensing instrument and mission introduced as the remote sensing instrument and mission parameters are specified.parameters are specified.

PowerfulPowerful activeactive remoteremote sensorsensor systemssystems thatthat emitemit theirtheirl t til t ti di tidi ti (( LIDARLIDAR RADARRADARownown electromagneticelectromagnetic radiationradiation (e(e..gg..,, LIDAR,LIDAR, RADAR,RADAR,

SONAR)SONAR) cancan bebe intrusiveintrusive andand affectaffect thethe phenomenonphenomenonbeingbeing investigatedinvestigated.. AdditionalAdditional researchresearch isis requiredrequired totogg ggdeterminedetermine howhow intrusiveintrusive thesethese activeactive sensorssensors cancan bebe..

RemoteRemote sensingsensing instrumentsinstruments maymay becomebecome uncalibrateduncalibrated,,ltilti ii lib t dlib t d tt d td tresultingresulting inin uncalibrateduncalibrated remoteremote sensorsensor datadata..

RemoteRemote sensorsensor datadata maymay bebe expensiveexpensive toto collectcollect andandanalyzeanalyze HopefullyHopefully thethe informationinformation extractedextracted fromfrom thetheanalyzeanalyze.. Hopefully,Hopefully, thethe informationinformation extractedextracted fromfrom thetheremoteremote sensorsensor datadata justifiesjustifies thethe expenseexpense..

Problems Associated withProblems Associated with In SituIn Situ Data CollectionData Collection

ScientistsScientists cancan collectcollect datadata inin thethe fieldfield usingusing biasedbiasedproceduresprocedures oftenoften referredreferred toto asas methodmethod--producedproduced errorerror..S hS h bb i t d di t d d bbSuchSuch errorerror cancan bebe introducedintroduced byby::

sampling design does not capture the spatial variability of sampling design does not capture the spatial variability of the phenomena under investigation (i.e., some the phenomena under investigation (i.e., some phenomena or geographic areas are oversampled phenomena or geographic areas are oversampled p g g p pp g g p pwhile others are while others are undersampledundersampled))

improper operation ofimproper operation of in situin situ measurement instrumentsmeasurement instrumentsimproper operation of improper operation of in situ in situ measurement instrumentsmeasurement instruments

uncalibrateduncalibrated in situ in situ measurement instruments.measurement instruments.

Jensen, 2000

Spectral ResolutionResolution

Jensen, 2004

Airborne Visible Airborne Visible Infrared Imaging Infrared Imaging Spectrometer Spectrometer (AVIRIS)(AVIRIS) DatacubeDatacube ofof(AVIRIS) (AVIRIS) DatacubeDatacube of of Sullivans Island Sullivans Island Obtained on October Obtained on October 26 199826 199826, 199826, 1998Color-infrared colorcomposite on top p pof the datacube was created using three of the 224 bandsof the 224 bands at 10 nm nominal bandwidth.

Jensen, 2004

Spatial Spatial ResolutionResolutionResolutionResolution

Jensen, 2004

Temporal ResolutionTemporal ResolutionTemporal ResolutionTemporal Resolution

Remote Sensor Data AcquisitionRemote Sensor Data Acquisition

June 1, 2004June 1, 2004 June 17, 2004June 17, 2004 July 3, 2004July 3, 2004June 1, 2004June 1, 2004 June 17, 2004June 17, 2004 July 3, 2004July 3, 2004

16 days16 days

Jensen, 2004

Radiometric ResolutionRadiometric Resolution

77--bitbit(0(0 -- 127)127)0

88--bitbit(0(0 -- 255)255)0

(0 (0 127)127)

(0 (0 255)255)

99--bitbit(0(0 511)511)

0(0 (0 -- 511)511)

1010--bitbit(0 (0 -- 1023)1023)0 (( ))

Jensen, 2004