Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.
-
Upload
ashton-collins -
Category
Documents
-
view
218 -
download
2
Transcript of Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.
![Page 1: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/1.jpg)
Environmental Remote Sensing GEOG 2021
Lecture 2
Image display and enhancement
![Page 2: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/2.jpg)
2
Image Display and Enhancement
Purpose
• visual enhancement to aid interpretation • enhancement for improvement of information
extraction techniques
![Page 3: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/3.jpg)
3
Topics
• Display– Colour composites– Greyscale Display– Pseudocoluor
• Image arithmetic– +
• Histogram Manipulation– Properties – Transformations – Density slicing
![Page 4: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/4.jpg)
4
Colour Composites
‘Real Colour’ compositered band on red
green band on green
blue band on blue
Swanley, Landsat TM
1988
![Page 5: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/5.jpg)
5
Colour Composites
‘Real Colour’ compositered band on red
![Page 6: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/6.jpg)
6
Colour Composites
‘Real Colour’ compositered band on red
green band on green
![Page 7: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/7.jpg)
7
Colour Composites
‘Real Colour’ compositered band on red
green band on green
blue band on blue
approximation to ‘real colour’...
![Page 8: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/8.jpg)
8
Colour Composites
‘False Colour’ compositeNIR band on red
red band on green
green band on blue
![Page 9: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/9.jpg)
9
Colour Composites
‘False Colour’ compositeNIR band on red
red band on green
green band on blue
![Page 10: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/10.jpg)
10
Colour Composites
‘False Colour’ composite• many channel data, much not comparable to RGB
(visible)– e.g. Multi-polarisation SAR
HH: Horizontal transmitted polarization and Horizontal received polarizationVV: Vertical transmitted polarization and Vertical received polarizationHV: Horizontal transmitted polarization and Vertical received polarization
![Page 11: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/11.jpg)
11
Colour Composites‘False Colour’ composite• many channel data, much not comparable to RGB (visible)
– e.g. Multi-temporal data
– AVHRR MVC 1995
April
August
September
April; August; September
![Page 12: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/12.jpg)
12
Greyscale Display
Put same information on R,G,B:
August 1995
August 1995
August 1995
![Page 13: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/13.jpg)
13
Pseudocolour
• use colour to enhance features in a single band – each DN assigned a
different 'colour' in the image display
![Page 14: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/14.jpg)
14
Image Arithmetic
• Combine multiple channels of information to enhance features
• e.g. NDVI
(NIR-R)/(NIR+R)
![Page 15: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/15.jpg)
15
Image Arithmetic
• Combine multiple channels of information to enhance features
• e.g. NDVI
(NIR-R)/(NIR+R)
![Page 16: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/16.jpg)
16
Image Arithmetic
• Common operators: Ratio
Landsat TM 1992
Southern Vietnam:
green band
what is the ‘shading’?
![Page 17: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/17.jpg)
17
Image Arithmetic
• Common operators: Ratio
topographic effects
visible in all bands
FCC
![Page 18: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/18.jpg)
18
Image Arithmetic
• Common operators: Ratio (cha/chb)
apply band ratio
= NIR/red
what effect has it had?
![Page 19: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/19.jpg)
19
Image Arithmetic
• Common operators: Ratio (cha/chb)
• Reduces topographic effects
• Enhance/reduce spectral features
• e.g. ratio vegetation indices (SAVI, NDVI++)
![Page 20: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/20.jpg)
20
Image Arithmetic
• Common operators:• Subtraction
• examine CHANGE
MODIS NIR: Botswana Oct 2000
Predicted Reflectance
Based on tracking reflectance for previous period
![Page 21: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/21.jpg)
21
Image Arithmetic
Measured reflectance
![Page 22: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/22.jpg)
22
Image Arithmetic
Difference (Z score)
measured minus predicted
noise
![Page 23: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/23.jpg)
23
Image Arithmetic
• Common operators: Addition
– Reduce noise (increase SNR) • averaging, smoothing ...
– Normalisation (as in NDVI)
+
=
![Page 24: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/24.jpg)
24
Image Arithmetic
• Common operators: Multiplication• rarely used per se: logical operations?
– land/sea mask
![Page 25: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/25.jpg)
25
Histogram Manipluation
• WHAT IS A HISTOGRAM?
![Page 26: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/26.jpg)
26
Histogram Manipluation
• WHAT IS A HISTOGRAM?
![Page 27: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/27.jpg)
27
Histogram Manipluation
• WHAT IS A HISTOGRAM?
Frequency of occurrence (of specific DN)
![Page 28: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/28.jpg)
28
Density Slicing
![Page 29: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/29.jpg)
29
Density Slicing
![Page 30: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/30.jpg)
30
Density Slicing
Don’t always want to use full dynamic range of display
Density slicing:
• a crude form of classification
![Page 31: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/31.jpg)
31
Density Slicing
Or use single cutoff
= Thresholding
![Page 32: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/32.jpg)
32
Histogram Manipulation
• Analysis of histogram – information on the dynamic range and distribution
of DN• attempts at visual enhancement• also useful for analysis, e.g. when a multimodal
distribution is observed
![Page 33: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/33.jpg)
33
Histogram Manipulation
• Analysis of histogram – information on the dynamic range and distribution
of DN• attempts at visual enhancement• also useful for analysis, e.g. when a multimodal distibution
is observed
![Page 34: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/34.jpg)
34
Histogram Manipulation
Typical histogram manipulation algorithms:
Linear Transformation
input
outp
ut
0 255
255
0
![Page 35: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/35.jpg)
35
Histogram Manipulation
Typical histogram manipulation algorithms:
Linear Transformation
input
outp
ut
0 255
255
0
![Page 36: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/36.jpg)
36
Histogram Manipulation
Typical histogram manipulation algorithms:
Linear Transformation
• Can automatically scale between upper and lower limits•or apply manual limits
•or apply piecewise operator
But automatic not always useful ...
![Page 37: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/37.jpg)
37
Histogram Manipulation
Typical histogram manipulation algorithms:
Histogram EqualisationAttempt is made to ‘equalise’ the frequency distribution across the full DN range
![Page 38: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/38.jpg)
38
Histogram Manipulation
Typical histogram manipulation algorithms:
Histogram Equalisation
Attempt to split the histogram into ‘equal areas’
![Page 39: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/39.jpg)
39
Histogram Manipulation
Typical histogram manipulation algorithms:
Histogram Equalisation
Resultant histogram uses DN range in proportion to frequency of occurrence
![Page 40: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/40.jpg)
40
Histogram Manipulation
Typical histogram manipulation algorithms:
Histogram Equalisation
• Useful ‘automatic’ operation, attempting to produce ‘flat’ histogram
• Doesn’t suffer from ‘tail’ problems of linear transformation
• Like all these transforms, not always successful
• Histogram Normalisation is similar idea
• Attempts to produce ‘normal’ distribution in output histogram
• both useful when a distribution is very skewed or multimodal skewed
![Page 41: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/41.jpg)
41
Summary
• Display– Colour composites– Greyscale Display– Pseudocoluor
• Image arithmetic– +
• Histogram Manipulation– Properties– Density slicing– Transformations
![Page 42: Environmental Remote Sensing GEOG 2021 Lecture 2 Image display and enhancement.](https://reader035.fdocuments.net/reader035/viewer/2022062511/5515dafb550346d46f8b4a6e/html5/thumbnails/42.jpg)
42
Summary
• Followup:– web material
• http://www.geog.ucl.ac.uk/~plewis/geog2021• Mather chapters• Follow up material on web and other RS texts• Access Journals