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">
<p>By Petter Reinholdtsen and Shanette Dallyn, 2005-05-01.</p>
-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>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/
-Tried to use svalbard/tm87.img, but it only have 5 bands. Next tried
-jotunheimen/tm.img, which had 7 bands.
+<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.
-The pixel values in a given band is only a using a given range of
+<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.
+<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>
-<h3>band 1, blue (0.45-0.52 um)</h3>
+<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
peaks at 0 and 255. The mean value is 34.3403.
<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
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" -->
-<p>Comparing a map we found on the web,
-<img src="http://home.online.no/~oe-aase/jotunheimen/jotun2000topper.jpg">
-and the standard infrared image composition, we can identify some
-features from the colors used:
+<img width="40%" src="jotunheimen-std-ir.jpeg">
+
+<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>
<ul>
<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>
+ <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:
<tr><td>-1</td><td>-1</td><td>-1</td><td>-1</td><td>-1</td></tr>
</table></p>
-<p>This one gave more lines showing the borders between the thermal
+<p><img align="right" width="40%"src="jotunheimen-therm-unsharp5x5.jpeg">
+This one gave more lines showing the borders between the thermal
pixels.
From: shanette Dallyn <shanette_dallyn@yahoo.ca>