Rs lect 2day_1

Dr.-Ing. Görres Grenzdörffer Remote Sensing

Airborn Remote Sensing 1

Universität Rostock, Professur für Geodäsie und Geoinformatik X 2006

Dr.-Ing. Görres Grenzdörffer

Basics and Applications ofRemote SensingBasics and Applications ofRemote Sensing

Universität Rostock, Professur für Geodäsie und Geoinformatik

Schedule Lectures

• Remote Sensing Basics (1st Day)• Examples of modern airborne and spaceborne remote sensing• The EM-spectrum• Reflectance properties of different objects• Spaceborne sensors

• Satellite Remote Sensing (1st Day)• Resolution• Examples• SRTM• Change Detection

• Airborne Remote Sensing (2nd Day)• (digital) airborne sensors• Digital orthophotos• Digital oblique imagery

• Digital image Processing (2nd Day)• Pixels and mixels• Spectral bands / low level image operations• MS-classification• Object oriented classification



Universität Rostock, Professur für Geodäsie und Geoinformatik X 2006

Airborne Remote Sensing

Dr.-Ing. Görres Grenzdörffer


Photogrammetry

• Photogrammetry can be defined as the method of determining the shapes, sizes and positions of objects using photographs, and therefore it is an indirect method of measurements.

• Photogrammetric surveying uses photographs taken from an aircraft or terrestrial from the ground.

Z

X

Yobjects

Imagey

x

Z

XY

objects Image

x

z

from an aircraft from the ground




Mathematical fundamentals of photogrammetry

Z

X

Y

Real world

OImage

x

y

cK

N

The interior Orientation of theimaging camera (3 parameters):

xH, yH - image co-ordinates of nadir point N

cK - focal lenghtLC - Lens distortion

The exterior Orientation of theimaging camera (6 parameters):

XO, YO, ZO - the position of theperspective center O

ωO, ϕO, κO - the rotation of theperspective center O


Z

X

Y

Real world

OImage

x

y

A

a

xA = -cK

a1 (XA-XO) + a2 (YA-YO) + a3 (ZA-ZO)

c1 (XA-XO) + c2 (YA-YO) + c3 (ZA-ZO)

yA = -cK

b1 (XA-XO) + b2 (YA-YO) + b3 (ZA-ZO)

c1 (XA-XO) + c2 (YA-YO) + c3 (ZA-ZO)

Given: Co-ordinates of the object point A - (XA, YA, ZA)

Wanted:Co-ordinates of the image plane -(xA, yA)

Solution:

ai, bi, ci - Functions of theorientiation parameters

Mathematical fundamentals of photogrammetry




Aerial photogrammetry

• Aerial photogrammetry involves the use of photographs taken in a systematic manner from the air. They are then controlled by land survey and measured by photogrammetric techniques. Accuracy of aerial photogrammetry are comparable with those obtained by land survey, and in many cases the work is carried out more economically.

Flight track

Overlap 15-25%

Overlap ca. 60%

End lap > 50 % basic prerequisite for stereoscopic vision


Introduction – situation of analogue and digital airborne imaging systems

• Analogue imaging systems (airborne frame cameras) will remain at work for the next 5 - 10 years

• Digital is state of the art for data processing • Professional digital airborne imaging systems (e.g. DMC, ADS

40, Ultra Cam) are available and replace the analogue cameras • Additionally digital „low-cost“ systems are available for special

applications

• The digital „low-cost“ systems differ greatly in terms of performance, accuracy, price




Aerial mapping camera - Leica RC 30

Stabilized mount

Film magazineNavigationtelescope

Cameralense

Camera control/Data annotation

External camera controlby GPS/INS flight mana-gement system

Product information lh Systems


Data annotation of aerial survey camera

• Fiducial marks• Interior orientation, film displacement

• Time and Acquisition date• Changing situations, chronological,

sequence, reconstruction of the airspeed, Sun azimuth and direction

• Bubble level• Deviation from the vertical

• Altitude measure/ statoscope / GPS• Air pressure, Altitude above sea level

• Image scale Image number, camera number

• Information on the backside of the images

• Project, aerial survey company, focal length, exposure time etc.

Dietz, 1981

RC 30, digital annotation.




Advantages and disadvantages of digital sensors

• Advantages of digital sensors• Better radiometric and spectral properties• More flight hours, due to higher sensibility of the sensor • No film – no scanning• Data processing allows for higher degree of automation• Fit well into digital GIS-environment

• Problems with digital sensors• Large amount of data (Terabytes)• Turnaround time, especially with big projects (1 h flight 100 h

data processing)• Digital camera systems more expensive than analogue cameras


Geometric Resolution – scale and ground sampling distance (GSD) at analogue and digital cameras

Scale – a familiar term

1:50.000

1.00 m

0.50 m

0.25 m

1:40.0001:30.0001:20.0001:10.000

0.75 m

1.25 m Analogue, 25 µm (CIR)

Analogue, 15 µm (SW)

Digital, 12 µm (Color, CIR)

Digital, 6.5 µm (Color, CIR)

Scale from digital cameras ≠ analogue cameras

Image scale

Gro

und

sam

plin

g di

stan

ce (G

SD)




Digital Modular Camera DMC

Flight direction

Color camerasPan-cameras

Max. 4 panchromatic camerasMax. 4 multispectral cameras


DMC - data post processing




Principle of a three line scanner

F

RN

N

R

F

• On a flight line every object is covered from three different viewing angles

• Stereo measurement inherent (Stereo along track)

• Automatic Ortho photo generation• Requirement: Geocoding of any

image line !! with high accuracy GPS/INS

Systems: HRSC, ADS 40


Leica ADS 40 – three line scanner




Components of the ADS 40

1. Sensor unit with digital optics and INS2. Control unit with navigations computer3. Mass storage

4. User interface5. Navigation aerial survey6. Stabilized platform PAV 40

Fricker, 2001


Airborne Digital Sensor (ADS 40)

1h data acquisition> 50 h data processing !!

Focal length 62.77 mmTotal field of view 42.6° x 64°Number of CCD lines 10 (4 Color), 2 staggered

Lines for Pan-bandsStereo angle - 14.2°, +28.4°Swath width (FOW) 64°Pixel per CCD line 12.000Pixel size 6.5 x 6.5 µm²Radiometric Resolution 12 Bit pan 8 Bit MS

Blue: 430 - 490 nmGreen: 535 - 585 nmRed: 610 - 660 nm

Spectral resolution

NIR: 835 - 885 nmNadir/Stereo band (Pan) 465 - 680 nmReadout rate max. 833 Lines/secWeight camera 70 kgSystem Weight 180 kgStabilization Stabilized mount PAV 30,

GPS/INS from Applanix / IGIData storage MM 40 (max. 438 GB)




Influx of the radial terrain distortion in ortho photo generation of aerial images and 3- line scanners

Single image withCentral perspective

Photogrammetric block withcentral perspective images

Backward lookingstrip

Nadir lookingstrip

Forward lookingstrip

Aerial image 3- line scanner


Comparison of three line scanner technology with CCD-array sensors

Advantages CCD-array sensor Advantages three line scanner - a well definied, stable geometrie of the

acquired images - Direct Geo referencing with GPS/INS

(AT optional) - common, central perspective image

geometry - Highest automation and accuracy of

digital terrain models and ortho photos - Compatibility with the software of ex-

isting softcopy-systems - „True Orthophoto“ of nadir channel

- GPS/INS not necessary - Homogenious spectral properties within a single strip




PFIFF in action

Sport aeroplane(Cessna 172)

Ground hole

PhotographerNavigator / Copilot

12 cm


Resolution 4080 * 5440 Pixel Pixel size 9 * 9 µm Sensor size 36.9 * 48.9 mm Color mode Mosaic filter on Chip Color Either RGB or CIR Color depth per channel 12 Bit (= 4096 Gray values File size (8 Bit) 66 MB Min. exposure interval ca. 3 Sec. Min. ground resolution ca. 8 cm at 60 % End lap Weight (inkl. camera) ca. 1.800 g Computer connection Firewire IEEE, Barebone PC Software Phase One

Rollei AIC 45 CIR




Image processing - from aerial survey to 3D- information

• Survey planning und flight• Aerotriangulation with min. number of GCP‘s• Orthophoto generation• Mosaicking und color balancing• Delivery of „GIS-ready“ data within a few

days or weeks• 2D/3D-data analysis


Forestry – aerial surveys for disease detection (pine looper)

Flight parameters• Altitude: ca. 750 m• GSD: ca. 12 cm• Date: 15.1.2006• Area: 35 km²• No. of Images: 210• Image 59.100 * 48700 pixel• Georeferencing: 3 days

1 km1 km

• Funding / Partner• State forestry department

• Goals• Detection of infected / infested trees

of pine looper by CIR-Images• Determination of exact locations for

chemical forest treatment of pine looper

• Special issues• High resolution images for single

tree detection• less one week for orthophoto

generation• Aerial survey during winter time

(light conditions)





Pine looper infestion of pine trees

• Small plots of infected areas• The pine looper causes up 100 % loss of needles

Bupalus piniarius (L.)




Student project digital village planning – winter semester 05/06

• Course objectives• Basic practical knowledge of photogrammetry and GIS for rural

planning• Investigation of potential roofs for solar energy panels based on

digital photogrammetric data• Data

• Digital aerial survey of the small village (ca. 800 inhabitants)Parkentin

• Digital topographic base Information (Maps, historic maps parcelcadastre, DEM, etc.)

• Project work• Generation of digital orthophoto mosaic, • Stereo mapping of houses, trees, roads etc.• Data base of house attributes (height, no. of floors, age, roof

material, ridge direction, etc.• Calculation of potential shading due to house and tree obstruction• Identification of suited buildings for solar panels on their roofs• Comparison of current and historical land use


Digital Orthophoto Mosaic Parkentin – 23.11.2005

Flight height: ca. 700 mNumber Images: 35GSD: 12 cm / Pixel

Flight height: ca. 700 mNumber Images: 35GSD: 12 cm / Pixel




Detail 1: 500


Suitable roofs for solar panels – data base query

CriteriaCriteria::RidgeRidge directiondirection SE SE –– SW,SW,RoofRoof inclinationinclination 3535°° –– 45 45 °°,,No No thatchedthatched roofroofRoofRoof > 60 m> 60 m²²




Suitable roofs for solar panels – final visual control of roof structures

suitablesuitablepartlypartly suitablesuitablenotnot suitablesuitable

CriteriaCriteria::RidgeRidge directiondirection SE SE –– SW,SW,RoofRoof inclinationinclination 3535°° –– 45 45 °°,,No No thatchedthatched roofroofRoofRoof > 60 m> 60 m²²No No shadeingshadeing, , UsableUsable roofroof areaarea > 60 m> 60 m²²


Settlement- and land use development 1875 - 2005




Image scale of a nadir image

c = focal length (calibrated value)

hg = flight height above ground

O = Perspective center

S = Distance on ground

Sk = Distance in map

s' = Distance in image

Mb = Image scale

Mk = Map scale

c

S

hg

Ground plane(Map plane)

Image plane

Mb = 1mb

chg

s'S

s'Sk * mk

= = =

s'


Relief displacement due to central perspective

The relief displacement is radial to the image nadir• Points above the nadir level are displaced towards the image edges• Points below the nadir level are displaced towards the image center

Löffler, 1985

Imhof, 1958




Principle of digital ortho image generation

O

Digitalterrainmodel

Orthophoto

Analogue image

Digital image

Input: Digital imageDigital terrain modelImage orientation parameter

Processing:Differential resamplingRadiometric CorrectionsMosaicking

Output:Digital OrthophotosThematic MapsDigital Orthophoto Maps


O

x0

0y

xys

sdigital image

DTM

Ortho photo

Why are digital ortho images necessary

Prerequisite for

• GIS-Integration

• On-Screen digitizing

• Update digitizing

• Monitoring

• Change detection

Ortho photos correct terrain induced displacements only at the surface, roofs, trees etc. are not displayed at their right position !!




A seamless orthophoto mosaik isderived from many single images

Radiometric differences occur dueto changes in viewing perspective, atmosphere, BRDF …

Options

• Histogram matching

• Color balancing

Mosaicking

• Dodging


Orthophotos for updating current cadastral base maps




AD

BC

d' d"

a' a"b' b"

t"t'c' c"

n2"n1'

O1 O2

T

n2"n1'

Stereoscopic vision

• The stereo vision is possible due to the simultaneous view of an object from two different viewing angles

• With our pair of eyes humans recognize an object from two perspectives, which are fused into one 3D-image in the brain.

• Instrumental stereoscopic vision requires two images (stereo pair), which:

• Show an object under two different viewing angles

• Have a similar image scale• Are taken from the same

perspective


Pocket stereoskope Mirror stereoskope Visopret

Mirror

Eye distance

RIght imageLeft image Instrument base

Mirror

Reflecting Prisms

ca 6,5 cm

ca. 21 cm

6,5 cm

10 cm

2,8 time enlargement2,8-15 time enlargement

Zeiss, 1994

Stereoskopes




Stereo measurement of digital aerial images

Prerequisites• Digital stereo image pairs /

photogrammetric blocks• Special software and stereo

glassesAdvantages• Correct 3D-measurement (no

terrain displacement)• Complete usage of the image

content• Geo referenced data "GIS-

Ready“Methods for digital stereo vision

• Anaglyph glasses• Shutter glasses• Polarization glasses





Trends and Outlook – Oblique images for Photogrammetryand 3D city Models

• In the past oblique images were generally taken for visualization purposes, rather than for metric applications

• Exemption: military sector were oblique images are a standard for reconnaissance purposes

• To fully exploit the information from the oblique perspective, a minimum of four images from all sides have to be acquired and managed.

• Standard GIS-packages do not support oblique images, due to their geometry with varying scales, therefore new viewers and software necessary, e.g. Pictrometry, Multivision, Virtual Earth ….

• Oblique images are difficult to obtain with standard mapping cameras

• Middle format camera(s) systems provide the necessary flexibility


Key applications of oblique images

• Tax Assessment and building code violations • Change Detection• Urban & infrastructure planning • Real estate surveys • Military, security, anti- terror and special forces operations• First response for police and fire fighters• Critical infrastructure protection for facilities such as airports,

seaports, chemical & power plants, government buildings and more




Flight pattern for test flight Rostock 23.11.2006

Altitude: ca. 400 mStrip distance: 400 mViewing angle: 45°GSD at image center: ca. 12 cm


Sample of oblique image (foreground)




Multivision Main Screen

Universität Rostock, Professur für Geodäsie und Geoinformatik - 52 -

With MultiVision, you can view, analyze and measure




Comparing Projects from 2 Periods for Change Detection

Secondary ProjectPrimary Project


Import of Shape files on Oblique images




Import of Shape files on Oblique images


Object height model

LOD 1 3D- building model on the basis of 2D- building geometry and an object height model (OHM)

2D-building geometry

Assignment of theelevation to the buildings

3D-block model

Rostock 3D with 34.096 buildings is available LOD 1




Rostock 3D- Model LOD 1 → LOD 2

• Semiautomatic 3D-buildings based on ALK

• Separation of „Multipart“ ALK-buildings

• Definition of roof type via building attribute

• CAD-construction of selected landmarks

• Texture generation of selected buildings with Multivision


Semiautomatic generation of building textures




MultiVision's 3D with ArcGlobe

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