</head>
<body>
- <h1></h1>
-Here are my notes from today.
+ <p><a href="http://www.geo.uio.no/geogr/geomatikk/oppgaver/bildeforbedring_eng.html">Assigment 8</a>
+ in <a href="http://www.uio.no/studier/emner/matnat/geofag/GEG2210/index-eng.html">GEG2210</a>
+ - Data Collection - Land Surveying, Remote Sensing and Digital
+ Photogrammetry</p>
+ <h1>Image enhancement, filtering and sharpening</h1>
+<img src="jotunheimen-ir-2band.jpeg">
+<img src="jotunheimen-truecolor.jpeg">
+<img src="jotunheimen-std-ir-eq.jpeg">
-Logged into jern.uio.no using ssh to run ERDAS Imagine. Started by
-using 'imagine' on the command line. The images were loaded from
-/mn/geofag/gggruppe-data/geomatikk/
+ <p>By Petter Reinholdtsen and Shanette Dallyn, 2005-05-01.</p>
-Tried to use svalbard/tm87.img, but it only have 5 bands. Next tried
-jotunheimen/tm.img, which had 7 bands.
+<p>This exercuse was performed by logging into jern.uio.no using ssh
+and runnign ERDAS Imagine. Started by using 'imagine' on the command
+line. The images were loaded from /mn/geofag/gggruppe-data/geomatikk/
-The pixel values in a given band is only a using a given range of
+<p>We tried to use svalbard/tm87.img, but it only have 5 bands. We
+decided to switch, and next tried jotunheimen/tm.img, which had 7
+bands.
+
+<p>The pixel values in a given band is only a using a given range of
values. This is because sensor data in a single image rarely extend
over the entire range of possible values.
-Evaluation of the different bands
-=================================
+<p>The peak values of the histograms represent the the spectral
+sensitivity values that occure the most often with in the image band
+being analysed.
+
+<h2>Evaluation of the different bands</h2>
-band 1, blue (0.45-0.52 um)
----------------------------
+<h3>band 1, blue (0.45-0.52 micrometer - um)</h3>
Visible light, and will display a broad range of values both over
land and water. Reflected from ice, as those are visible white and
30 and 136. Mean values of 66.0668. There are one wide peak with
center around 50. There are two peaks at 0 and 255.
-band 2, green (0.52-0.60 um)
-----------------------------
+<h3>band 2, green (0.52-0.60 um)</h3>
Visible light, and will display a broad range of values both over
land and water. Reflected from ice, as those are visible white and
to 120. The mean value is 30.9774. There are two main peaks at 20
and 27. There is also a pie at 0.
-band 3, red (0.60-0.69 um)
---------------------------
+<h3>band 3, red (0.60-0.69 um)</h3>
Visible light, and will display a broad range of values both over
land and water. Reflected from ice, as those are visible white and
t 135, with one wide peak around 52. There are also seem to be two
peaks at 0 and 255. The mean value is 34.3403.
-band 4, near-infraread (0.76-0.90 um)
--------------------------------------
+<h3>band 4, near-infraread (0.76-0.90 um)</h3>
+<img align="right" width="20%" src="jotunheimen-band4-hist.jpeg">
Water acts as an absorbing body so in the near infrared spectrum,
water features will appear dark or black meaning that all near
show most values between 7 and 110. The mean is 40.1144. There are
two peaks at 7 and 40.
-band 5, mid-infrared (1.55-1.75 um)
------------------------------------
+<h3>band 5, mid-infrared (1.55-1.75 um)</h3>
The ice, glaciers and water do not reflect any mid-infrared light.
The histogram show most values between 1 and 178. The mean is
49.8098 and there are two peaks at 6 and 78, in addition to two
peaks at 0 and 255.
-band 6, thermal infrared (10.4-12.5 um)
----------------------------------------
+<h3>band 6, thermal infrared (10.4-12.5 um)</h3>
Display the temperature on earth. We can for example see that the
ice is colder than the surrounding areas. The histogram show most
values between 36 to 122. The mean is 102.734. There are one wide
peak around 53, in addition to two peaks at 0 and 255.
-band 7, mid-infrared (2.08-2.35 um)
-------------------------------------
+<h3>band 7, mid-infrared (2.08-2.35 um)</h3>
The ice, glaciers and water do not reflect any mid-infrared
frequencies. The histogram show most values between 77 and 150.
The mean is 24.04, and there are one wide peak at 130 and a smaller
peak at 83, in addition to one peak at 0.
-Image enhancement
------------------
+<h3>Image enhancement</h3>
We can get a good contrast stretch by using the histogram
equalisation. This will give us the widest range of visible
separation between features.
-Displaying colour images
-------------------------
+<h3>Displaying colour images</h3>
+
+<p><img width="40%" src="http://home.online.no/~oe-aase/jotunheimen/jotun2000topper.jpg">
+<!-- img src="jotunheimen-map.jpeg" -->
+
+<img width="40%" src="jotunheimen-std-ir.jpeg">
-Comparing a map we found on the web,
-<URL:http://home.online.no/~oe-aase/jotunheimen/jotun2000topper.jpg.>
-and the standard infrared image composition, we can identify some
-features from the colors used:
+<p>Comparing a map we found on the web, and the standard infrared
+image composition, we can identify some features from the colors
+used:</p>
- - water is black or green
+<ul>
- - ice and glaciers are white, while snow is light green.
+ <li>water is black or green
- - vegetation is red.
+ <li>ice and glaciers are white, while snow is light green.
- - non-vegetation is brown or dull red when closer to snow and
+ <li>vegetation is red.
+
+ <li>non-vegetation is brown or dull red when closer to snow and
glaciers.
-Next, we tried to shift the frequencies displayed to use blue for the
+</ul>
+
+<p>Next, we tried to shift the frequencies displayed to use blue for the
red band, green for the near ir band and red for the mid ir (1.55-1.75
um). With this composition, we get some changes in the colours of
different features:
- - water is black
+<ul>
+ <li>water is black
+
+ <li>ice and glaciers are light blue, while snow is dark blue.
- - ice and glaciers are light blue, while snow is dark blue.
+ <li>vegetation is light green and yellow.
- - vegetation is light green and yellow.
+ <li>non-vegetation is red or brown.
- - non-vegetation is red or brown.
+</ul>
-Filtering and image sharpening
-==============================
+<h2>Filtering and image sharpening</h2>
-We decided to work on the grey scale version of the thermal infrared.
+<p>We decided to work on the grey scale version of the thermal infrared.
This one has lower resolution then the rest of the bands, with 120m
spatial resolution while the others have 30m spatial resolution.
-The high pass filtering seem to enhance the borders between the
+<p>The high pass filtering seem to enhance the borders between the
pixels. Edge detection gave us the positions of glaciers and water.
We tried a gradient filter using this 3x3 matrix: [ 1 2 -1 / 2 0 -2 /
1 -2 -1 ]. It gave a similar result to the edge detection.
-We also tried unsharp filtering using this 3x3 matrix: [ -1 -1 -1 / -1
+<p>We also tried unsharp filtering using this 3x3 matrix: [ -1 -1 -1 / -1
8 -1 / -1 -1 -1 ]. This gave similar results to the edge detection
too.
-We started to suspect that the reason the 3x3 filters gave almost the
+<p>We started to suspect that the reason the 3x3 filters gave almost the
same result was that the fact that the spatial resolution of the
thermal band is actually 4x4 pixels. Because of this, we tried with a
5x5 matrix, making sure it sums up to 0.
- -1 -1 -1 -1 -1
- -1 -1 -1 -1 -1
- -1 -1 24 -1 -1
- -1 -1 -1 -1 -1
- -1 -1 -1 -1 -1
+<p><table align="center">
+ <tr><td>
+ <tr><td>-1</td><td>-1</td><td>-1</td><td>-1</td><td>-1</td></tr>
+ <tr><td>-1</td><td>-1</td><td>-1</td><td>-1</td><td>-1</td></tr>
+ <tr><td>-1</td><td>-1</td><td>24</td><td>-1</td><td>-1</td></tr>
+ <tr><td>-1</td><td>-1</td><td>-1</td><td>-1</td><td>-1</td></tr>
+ <tr><td>-1</td><td>-1</td><td>-1</td><td>-1</td><td>-1</td></tr>
+ </table></p>
Next, we tried some different weight:
- -1 -1 -1 -1 -1
- -1 -2 -2 -2 -1
- -1 -2 32 -2 -1
- -1 -2 -2 -2 -1
- -1 -1 -1 -1 -1
+ <p><table align="center">
+ <tr><td>-1</td><td>-1</td><td>-1</td><td>-1</td><td>-1</td></tr>
+ <tr><td>-1</td><td>-2</td><td>-2</td><td>-2</td><td>-1</td></tr>
+ <tr><td>-1</td><td>-2</td><td>32</td><td>-2</td><td>-1</td></tr>
+ <tr><td>-1</td><td>-2</td><td>-2</td><td>-2</td><td>-1</td></tr>
+ <tr><td>-1</td><td>-1</td><td>-1</td><td>-1</td><td>-1</td></tr>
+ </table></p>
+<p><img align="right" width="40%"src="jotunheimen-therm-unsharp5x5.jpeg">
This one gave more lines showing the borders between the thermal
pixels.
<address><a href="mailto:pere@hungry.com">Petter Reinholdtsen</a></address>
<!-- Created: Sun May 1 13:25:38 CEST 2005 -->
<!-- hhmts start -->
-Last modified: Sun May 1 13:32:31 CEST 2005
+Last modified: Sun May 1 14:28:48 CEST 2005
<!-- hhmts end -->
</body>
</html>
projects / homepage.git / blobdiff