T3-Colour Composite Contrast_2010_v3_3slides_lowres

T3-Colour Composite Contrast_2010_v3_3slides_lowres -...

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1 Geography 333 Remote Sensing I Topic 3: Colour Theory, Multiband Images, Contrast Enhancement 2 Readings This class: Chapter 4 & Chapter 5 pg 152-164 (Image Quality, Histograms, Image Display) Next class: Chapter 2 (Sensors) & Chapter 6 (Radiation Principles) p 194- 222 Required Texts Jensen, J. R., 2005: Introductory Digital Image Processing: A Remote Sensing Perspective . Prentice Hall. 3 Today's new topics Raster data model review Basic colour theory Colour composites and multiband images Lookup tables and pseudocolour tables Histograms and scatterplots Contrast manipulation Gray-level thresholding Density slicing Contrast stretching
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2 4 Bands : Temporary holding spots in ENVI to al ow viewing; data from layers is loaded as you choose to display as Red/Green/Blue Sensor measures radiance in discrete wavelength bands B a n d 1 ( .4 5 - .5 2 u m ) 7 .0 8 .3 1 Values are stored as DNs in database channels ; each channel in the file physical y stores one band of data 1 2 3 Data stored in image planes are temporary! However, they can also be saved back to a physical channel in the database. NOTE: image plane 3 can be stored in database channel 7 (numbers do not need to align) ENVI: The software package used for image visualization and manipulation 5 Raster Data Model Based on grid cells, or pixels Each grid cell holds one attribute (brightness as DN) Are easy to process Remote sensing data is nearly always in the form of rasters 6 Computer Storage of Information Bits = B inary digITS ; the building block of computer information storage A single binary value (0 or 1) 8 bits equal 1 byte Unit used to represent most characters and numbers
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3 7 The Decimal System of Numbers Consider the number 193 3 * 10 0 9 * 10 1 1 * 10 2 3 9 1 1’s 10’s 100’s 8 The Binary System of Numbers Same concept, but with base 2 Consider the base 10 number 193 (= 128 + 64 + 1) 0 0 * 2 5 32’s 0 * 2 0 0 * 2 1 0 * 2 2 0 * 2 3 0 * 2 4 1 * 2 6 1 * 2 7 0 4’s 0 8’s 1 0 0 1 1 1’s 2’s 16’s 64’s 128’s 9 8-bit (1 byte) vs. 16-bit (2 bytes) 8 bit = 2 8 = (0 to 255) 0 = 00000000 1 = 00000001 2 = 00000010 3 = 00000011 254 = 11111110 255 = 11111111 16 bit = 2 16 = (0 to 65535) 0 = 0000000000000000 1 = 0000000000000001 2 = 0000000000000010 3 = 0000000000000011 65534 = 1111111111111110 65535 = 1111111111111111
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4 10 Common Digital Image Formats 8 bit integer = 1 Byte 0-255 Common for satellite imagery Unsigned 16 bit integer 0-65535 Common for Radar imagery Signed 16 bit integer – one bit is used for sign -32767 to +32767 Common for Digital Elevation Models 32 and 64 bit real – has fraction/decimal component Different bytes used for mantissa and exponent Often referred to as single and double precision Mantissa : The positive fractional part of the
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This note was uploaded on 01/18/2011 for the course GEOG 331 taught by Professor Staff during the Fall '08 term at Kansas.

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T3-Colour Composite Contrast_2010_v3_3slides_lowres -...

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