Photogrammetry and Multispectral Remote Sensing Lecture 3 September 8, 2004.

Photogrammetry and Multispectral Remote Sensing

Lecture 3

September 8, 2004

What is Photogrammetry

Photogrammetry is the art and science of making accurate measurements by means of aerial photography: Analog photogrammetry (hard-copy photos) Digital photogrammetry (digital images)

Aerial photographs were the first form of remote sensing imagery.

Differences between photogrammetry and Remote Sensing are that photographs are: Black and white (1 band) or color (blue, green, red, and IR) Wavelength range of 0.3-1.0 m Use cameras One type of remote sensing imagery

Types of vantage points to acquire photographs

Vertical vantage points Low-oblique vantage points High-oblique vantage points

GooseneckGoosenecks of the s of the

San Juan San Juan River River in Utahin Utah

GooseneckGoosenecks of the s of the

San Juan San Juan River River in Utahin Utah

Vertical Aerial PhotographyVertical Aerial PhotographyVertical Aerial PhotographyVertical Aerial Photography

Jensen, 2000Jensen, 2000Jensen, 2000Jensen, 2000

Altitude above-ground- level (AGL)

Vertical Aerial Photograph Over

Level Terrain

Principal point (PP)

Optical axis

Camera film plane

field of view

Altitude above-ground- level (AGL)

Vertical Aerial Photograph Over

Level Terrain

Principal point (PP)

Optical axis

Camera film plane

field of view

Most are vertical aerial photography

Low-oblique photograph of a bridge Low-oblique photograph of a bridge on on

the Congaree River near Columbia, the Congaree River near Columbia, SC.SC.

Low-oblique photograph of a bridge Low-oblique photograph of a bridge on on

the Congaree River near Columbia, the Congaree River near Columbia, SC.SC.

Low-oblique Aerial PhotographyLow-oblique Aerial PhotographyLow-oblique Aerial PhotographyLow-oblique Aerial Photography


Low-Oblique Aerial Photograph Over

Flat Terrain

Horizon is not shown in photograph

Optical axis

field of view

Low-Oblique Aerial Photograph Over

Flat Terrain

Horizon is not shown in photograph

Optical axis

field of view

High-oblique photograph of the High-oblique photograph of the grand Coulee Dam in Washington grand Coulee Dam in Washington

in 1940in 1940

High-oblique photograph of the High-oblique photograph of the grand Coulee Dam in Washington grand Coulee Dam in Washington

in 1940in 1940

High-oblique Aerial PhotographyHigh-oblique Aerial PhotographyHigh-oblique Aerial PhotographyHigh-oblique Aerial Photography


High-Oblique Aerial Photograph Over

Flat Terrain

Horizon is shown in the photographOptical

axis

field of view

High-Oblique Aerial Photograph Over

Flat Terrain

Horizon is shown in the photographOptical

axis

field of view

Color Science

Additive primary colors : Blue, Green, and Red

Subtractive primary colors (or complementary colors): Yellow, Magenta, and Cyan

Filters (subtract or absorb some colors before the light reaches the camera): Red filter (absorbs green and blue, you can

red) Yellow (or minus-blue) filter (absorbs

blue, allows green and red to be transmitted, which is yellow)

Haze filter (absorbs UV)

additive

Subtractive

Types of photographs

Black and white photographs Panchromatic (minus-blue filter used to eliminate UV and blue

wavelengths) IR (IR-sensitive film and IR only filter used to acquire photographs at

0.7- 1.0 m ) UV (at 0.3-0.4 m, low contrast and poor spatial resolution due to

serious atmospheric scattering) Color photographs

Normal color (Haze filter used to absorb UV and create true color 0.4-0.7 m, or blue, green, red)

IR color (Yellow filter used to eliminate blue and create IR color of 05-1.0 m, or green, red, IR)

4 bands (blue, green, red, and IR)

Satellite photographs

Extensive collections of photographs have been acquired from manned and unmanned Earth or Mars-orbiting satellites. Beginning in 1962, USA acquired photographs of moon for Apollo

mission 1995, USA declassified intelligence satellites photographs of Sino-

Soviet acquired 1960-1972 at 2-8 m resolution. 2000, Russia launched satellites acquired photographs of 2 meter

resolution 1999, Mars Global Surveyor of NASA acquires Mars photographs

with 1.2 – 12 m resolution 2003, Mars Express of ESA acquires Mars photographs with 2 and

10 m resolution.

Flightline of Vertical Aerial Photography Flightline of Vertical Aerial Photography Flightline of Vertical Aerial Photography Flightline of Vertical Aerial Photography


Exposure station #1

stereoscopic model

#2 #3

Direction of Flight

terrain recorded on three successive photographs

lens altitude above ground level, H

60% overlap

Coverage of photograph

Flightline of Aerial Photography

Exposure station #1

stereoscopic model

#2 #3

Direction of Flight

terrain recorded on three successive photographs

lens altitude above ground level, H

60% overlap

Coverage of photograph

Flightline of Aerial Photography

Block of Vertical Aerial Photography Block of Vertical Aerial Photography Block of Vertical Aerial Photography Block of Vertical Aerial Photography


20 – 30% sidelap

oblique photography may be acquired at the end of a flightline as the aircraft

banks to turn

Flightline #3

Flightline #2

Block of Aerial Photography

Flightline #1

20 – 30% sidelap

oblique photography may be acquired at the end of a flightline as the aircraft

banks to turn

Flightline #3

Flightline #2


Flightline #1

Block of Vertical Block of Vertical Aerial Photography Aerial Photography Compiled into an Compiled into an

Uncontrolled Uncontrolled Photomosaic Photomosaic

Block of Vertical Block of Vertical Aerial Photography Aerial Photography Compiled into an Compiled into an

Uncontrolled Uncontrolled Photomosaic Photomosaic


4-44-54-6

3-63-53-4


Compiled into an Uncontrolled

Photomosaic

a.

b.

4-44-54-6

3-63-53-4


Compiled into an Uncontrolled

Photomosaic

a.

b.

Columbia, SCColumbia, SCOriginal scale = 1:6,000Original scale = 1:6,000Focal length = 6” (152.82 Focal length = 6” (152.82

mm)mm)March 30, 1993 March 30, 1993

Columbia, SCColumbia, SCOriginal scale = 1:6,000Original scale = 1:6,000Focal length = 6” (152.82 Focal length = 6” (152.82

mm)mm)March 30, 1993 March 30, 1993

Scale of photographs

Principal Point

Optical axis

Camera lens

Focal length, f

A B

a b

o

P

Positive print

Real-world object space

Image space

Altitude above ground level,

H

Exposure Station, L

Principal Point

Optical axis

Camera lens

Focal length, f

A B

a b

o

P

Positive print

Real-world object space

Image space

Altitude above ground level,

H

Exposure Station, L

Image size/ real world size : S = ab/AB

Focal length/ altitude above ground: S = f / H

Scale (2)

56.1’

0.113”

6’

0.012”

56.1’

0.113”

6’

0.012”

1’ = 12 ”

0.012/ (6 x 12) = 1/6000

Average elevation above sea level,

h

Camera lens

Focal length f

Exposure station, L

A B

e go

P

Sea level

C

D

Highest elevation above sea level,

h max

Lowest elevation above sea level,

hmin

c d

Altitude above

sea level H

E

G

a bImage space

Object space

Average elevation above sea level,

h

Camera lens

Focal length f

Exposure station, L

A B

e go

P

Sea level

C

D

Highest elevation above sea level,

h max

Lowest elevation above sea level,

hmin

c d

Altitude above

sea level H

E

G

a bImage space

Object space

S = f / (H-h)

Max scale, minimum scale, and average or nominal scale

Orthophotographs and digital orthoimagery

Photograph after corrected by ground control points (x, y, z) or digital elevation model (DEM) called orthophotograph, orthophoto, or digital orthoimagery.

Not as photographs, they have different scales in different terrain relief, orthophotos have only one scale, no distortion, and have true distance, angle, and area. Orthophotos can be directly input into GIS as basemap or for interpretation.

Extraction of Building Infrastructure based on orthophotographs

Extraction of Building Infrastructure based on orthophotographs

Orthophotograph draped over a DEMOrthophotograph draped over a DEM

Kevin Hankinson will share his experience in acquiring aerial

photos

Multispectral Remote Sensing

Multispectral remote sensing is defined as the collection of reflected, emitted, or backscattered energy from an object or area of interest in multiple bands of electromagnetic spectrum; while Hyperspectral remote sensing involves data collection in hundreds of bands.

Instead of cameras and 1 or 4 bands for photogrammetry, Remote sensing use detectors that are sensitive to hundreds of bands in the electromagnetic spectrum. Measurements made by detectors are always stored in a digital format.

Overview Overview Overview Overview


Energy detected is recorded as an analog electrical signal

Remote Sensing Raster (Matrix) Data FormatRemote Sensing Raster (Matrix) Data Format Remote Sensing Raster (Matrix) Data FormatRemote Sensing Raster (Matrix) Data Format

0

127

255

Brightness value range

(typically 8 bit)Associated gray-scale

10 15 17 20

15 16 18 21

17 18

20

22

18

20

22 24

1

2

3

4

1 5432Columns ( j)

Bands (k )

1

2

3

4

X axis Picture element (pixel) at location Line 4, Column 4, in Band 1 has a Brightness Value of 24, i.e., BV4,4,1 = 24 .

black

gray

white21

23

22

25

Lines or rows (i)

0

127

255

Brightness value range

(typically 8 bit)Associated gray-scale

10 15 17 20

15 16 18 21

17 18

20

22

18

20

22 24

1

2

3

4

1 5432Columns ( j)

Bands (k )

1

2

3

4

X axis Picture element (pixel) at location Line 4, Column 4, in Band 1 has a Brightness Value of 24, i.e., BV4,4,1 = 24 .

black

gray

white21

23

22

25

Lines or rows (i)


Y axis

Jensen, 2000Jensen, 2000

Scanning Mirror

and Discrete Detectors

Lens

Scan mirror

Linear Array “pushbroom”

Objective

b.

Dispersing element

Lens

Collimator

Slit

Objective

Hyperspectral Area Array

d.

a.

c.

Linear Array “whiskbroom” Dispersing

elementLens

Collimator

Objective aperture

Scan mirror

Blue

NIRBlue

NIR

e.

Lens and filtration

Digital Frame Camera Area

Arrays

Detectors (multiple arrays)

Detectors

Scanning Mirror

and Discrete Detectors

Lens

Scan mirror

Linear Array “pushbroom”

Objective

b.

Dispersing element

Lens

Collimator

Slit

Objective

Hyperspectral Area Array

d.

a.

c.

Linear Array “whiskbroom” Dispersing

elementLens

Collimator

Objective aperture

Scan mirror

Blue

NIRBlue

NIR

e.

Lens and filtration

Digital Frame Camera Area

Arrays

Detectors (multiple arrays)

Detectors

Detector configurations: breaking ou the spectrum

Discrete Detectors and scanning mirrors

- MSS, TM, ETM+, GOES, AVHRR, SeaWiFS, AMS, ATLAS

Linear Arrays

- SPOT, IRS, IKONOS, ORBIMAGE, Quickbird, ASTER, MISR

Liner and area arrays

- AVIRIS, CASI, MODIS, ALI, Hyperion, LAC

Field of View (FOV), Instantaneous Field of View (IFOV)Dwell time is the time required for the detector IFOV to sweep across a ground cell. The longer dwell time allows more energy to impinge on the detector, which creates a stronger signal.

Sabin, 1997

Discrete Detectors and scanning mirrorsLiner arrays and area arrays


Landsat satellite series

MSS TM ETM+0.5-0.6 0.45-0.52 0.45-0.520.6-0.7 0.52-0.60 0.52-0.610.7-0.8 0.63-0.69 0.63-0.690.8-1.1 0.76-0.90 0.78-0.9010.4-12.6 1.55-1.75 1.55-1.75 10.4-12.5 10.4-12.5 2.08-2.35 2.09-2.35 0.52-0.9079m 30 30240m 120 60 156 bits 8 8103 m/c 99 9918 days 16 16 919km 705 705185km 185 185

Inclination (99º) of the Landsat Orbit to Inclination (99º) of the Landsat Orbit to Maintain A Sun-synchronous OrbitMaintain A Sun-synchronous Orbit

Inclination (99º) of the Landsat Orbit to Inclination (99º) of the Landsat Orbit to Maintain A Sun-synchronous OrbitMaintain A Sun-synchronous Orbit

99Þ

Landsat at 12:30 p.m. local time

Equatorial plane and

direction of Earth

rotation

Landsat at 9:42 a.m. local time

N

S

99Þ

Landsat at 12:30 p.m. local time

Equatorial plane and

direction of Earth

rotation

Landsat at 9:42 a.m. local time

N

SJensen, 2000Jensen, 2000Jensen, 2000Jensen, 2000

Sun-synchronous orbit mean that the orbital plane precessed around Earth at the same angular rate at which Earth moved around the Sun

The satellite cross the equator at approximately the same local time (9:30 to 10:00 am)

MSS 99ºTM 98.2º

Today’s Landsat 7 orbits and acquisition

http://landsat7.usgs.gov/pathrows.php

TexasView Remote Sensing Consortium

http://www.texasview.org/pages/archives/html/landsat.html

Free Landsat 7 imagery available from TexasView

About the lab setup and a DEMO of ENVI

Photogrammetry and Multispectral Remote Sensing Lecture 3 September 8, 2004.

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