Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data...
-
date post
15-Jan-2016 -
Category
Documents
-
view
215 -
download
0
Transcript of Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data...
![Page 1: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/1.jpg)
Lecture 2 Photographs and digital mages
Friday, 7 January 2011
Reading assignment:
Ch 1.5 data acquisition & interpretationCh 2.1, 2.5 digital imagingCh 3.3 scale
1
![Page 2: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/2.jpg)
What was covered in the previous lecture
2
LECTURES• Jan 05 1. Intro previous• Jan 07 2. Images today
Jan 12 3. PhotointerpretationJan 14 4. Color theoryJan 19 5. Radiative transferJan 21 6. Atmospheric scatteringJan 26 7. Lambert’s LawJan 28 8. Volume interactionsFeb 02 9. SpectroscopyFeb 04 10. Satellites & ReviewFeb 09 11. MidtermFeb 11 12. Image processingFeb 16 13. Spectral mixture analysisFeb 18 14. ClassificationFeb 23 15. Radar & LidarFeb 25 16. Thermal infraredMar 02 17. Mars spectroscopy (Matt Smith)Mar 04 18. Forest remote sensing (Van Kane)Mar 09 19. Thermal modeling (Iryna Danilina)Mar 11 20. ReviewMar 16 21. Final Exam
Introduction
•Remote sensing•Images, maps, & pictures•Images and spectra•Time series images•Geospatial analysis framework•Useful parameters and units•The spectrum
![Page 3: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/3.jpg)
Tuesday’s lecture was an introduction to remote sensingWe discussed:
what remote sensing wassomething about maps, images, and spectratime-series images - movieswhat was to be covered in this class
Today we discuss imaging systems and some of their characteristics
Specialized definitions:
scene the real-world target or landscape image a projection of the scene onto the focal plane of a camera picture some kind of representation of the image (e.g., hard copy)
3
![Page 4: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/4.jpg)
An imaging system
- scene
- optics
- (scan mirrors)
- focal plane
- detectors (film, CCD, etc.)
4
![Page 5: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/5.jpg)
Photographs
When it is enlarged enough, a photo gets fuzzy
A photo can be made incolor using dye layers
5
Photographs utilize concentrations of opaque grains to represent brightnesses
![Page 6: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/6.jpg)
Digital Images
CCD silicon wafer solid-state electronic component array of individual light-sensitive cells each = picture element (“pixel”)
Each CCD cell converts light energy into electrons.
A digital number (“DN”) is assigned to each pixel based on the magnitude of the electrical charge.
A Charged Couple Device replaces the photographic film.
In the case of digital cameras: Each pixel on the image sensor has red, green, and blue filters intermingled across the cells in patterns designed to yield sharper images and truer colors.
6
![Page 7: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/7.jpg)
Digital images
Each pixel is assigned a DN
0 200
198
168
199
75
100
100
100
75 75
75
168167
168
0 0 0
0
0
0
0 0
0
0
0
0
198
198
198
0 100 200 250
20
10
0
DN value
Num
ber
Histogram
7
![Page 8: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/8.jpg)
Digital images
When it is enlarged, a digital photo gets ‘pixilated’ Enlargement
8
![Page 9: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/9.jpg)
Important spatial properties in images
° Field of view (“FOV”) - Distance across the image (angular or linear)
° Pixel size- Instantaneous Field of view (“IFOV”) Size in meters or is related to angular IFOV and height above groundex: 2.5 milliradian, at 1000 m above the terrain
1000 m * (2.5 * 10-3 rad) = 2.5 m
Each pixel represents a ~square area in the scene that is a measure of the sensor's ability to resolve objects
Examples:Landsat 7 / ASTER VIS 15 metersLandsat 5 / ASTER NIR 30 metersASTER TIR 90 meters
9
![Page 10: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/10.jpg)
Radians defined
• Radian is a measure of angle, like degrees
• The circumference of a circle = 2 r, where r is its radius.
• There are 2 radians in a circle and 360 degrees
• A radian is therefore a little over 57 degrees
• 2.5 milliradians = 0.143 degrees
10
![Page 11: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/11.jpg)
IMAGE PROFILE
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0.45
0.5
0 10 20 30 40 50
DISTANCE
SIG
NA
L
Important spatial properties in images (continued)
TWO POINT SOURCES
0
0.2
0.4
0.6
0.8
1
1.2
0 10 20 30 40 50
DISTANCE
BR
IGH
TN
ESS
IMAGE PROFILE
0
0.1
0.2
0.3
0.4
0.5
0.6
0 10 20 30 40 50
DISTANCE
SIG
NA
L
Distance
Distance
DN
Bri
ghtn
ess
Two point sources
Image profile
Image profile: closer point sources
Distance
DN
° Resolution varies with object contrast, size, shape
11
![Page 12: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/12.jpg)
High contrast
Resolution, contrast & ‘noise’ affect detectability
Low contrast & blurred
12
Low signal/noise
![Page 13: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/13.jpg)
Large targets are more easily detected
13
Blurred, no measurement error with ‘noise’
![Page 14: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/14.jpg)
Recognition of shape is affected by resolving power
14
![Page 15: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/15.jpg)
Color information only, no spatial information (single pixel, three channels – Blue, , Green, & , & Red)
Resolution affects identification
15
What can be said in B/W? What can be said about color alone?Where does most of the useful information come from?
![Page 16: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/16.jpg)
Spectral information alone
Color information, no spatial information(single pixel, three channels – B, G, & R)
Spectrum – full “color” information,no spatial information
16
![Page 17: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/17.jpg)
What was covered in today’s lecture?
•Photographs and digital images•Structure of brightness elements in images•Detection•Resolution•Signal & noise•Point & extended targets
17
![Page 18: Lecture 2 Photographs and digital mages Friday, 7 January 2011 Reading assignment: Ch 1.5 data acquisition & interpretation Ch 2.1, 2.5 digital imaging.](https://reader035.fdocuments.net/reader035/viewer/2022062804/56649d5f5503460f94a3fbd8/html5/thumbnails/18.jpg)
Spatial data - photointerpretation & photogrammetry
18
What will be covered in Tuesday’s lecture