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Saturation And Value Saturation And Value Modulation: A New Method Modulation: A New Method For Integrating Colour And For Integrating Colour And
Grey-Scale ImageryGrey-Scale Imagery
David Viljoen & Jeff HarrisGeological Survey of Canada
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OverviewOverview
• Why integrate colour and grey-scale data?
• Conventional methods and problems.
• Saturation-Value-Modulation concept & SatValMod ArcGIS implementation.
• Geoscience examples.
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Integrating Colour & Grey-scale imageryIntegrating Colour & Grey-scale imagery
Enhancing the visualizationof a dataset.
DEM with shaded relief of DEM for Mt. Logan
}
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Integrating Colour & Grey-scale imageryIntegrating Colour & Grey-scale imagery
Visualizing the relationshipsbetween two datasets.
}K-Th-U (RGB) Gamma ray spectrometer with Landsat TM 7
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Layer transparencyLayer transparency20%
40%
60%
80%
80%
60%
40%
20%
Transparency of Colour
(Colour over shaded relief)
Transparency of shaded relief
(Shaded relief over colour)
Layer transparency control in ArcMap
Result is independentof layer order
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Red-Green-Blue coordinatesRed-Green-Blue coordinates
RGB used to define colours in computers and image files.
Integrating colour and greyscale imagery involves manipulation of coloursin RGB & HSV coordinate spaces.
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Hue–Sat–Value coordinatesHue–Sat–Value coordinates
Hue
ValueValue
V = 100
S = 1000º
120º
240º 0
100
0
100
0º 359º
SaturationSaturationHueHue
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Conventional Value ReplacementConventional Value Replacement
R
G
B
HH
SS
VV
R
G
B
RGB2HSV HSV2RGB
STOP
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Problems with Value ReplacementProblems with Value Replacement
• Loss/corruption of colour where: 1. Pixel colour is differentiated on Value (HSV)
2. Pixel colour has low saturation (achromatic axis of RGB cube)
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Problems with Value ReplacementProblems with Value Replacement
1. Pixel colour is differentiated on Value
R,G,B H,S,V
0,110,0 120,99,43
0,188,0 120,99,74
0,253,0 120,99,99
ReplaceV with pixelvalues from shaded relief
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Problems with Value ReplacementProblems with Value Replacement
2. Pixel colour has low saturation (achromatic axis of RGB cube)
… to replace the Values ofcolours with low saturation …
Using Values fromgrey-scale image …
… results in poorimage integration.
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Conventional RGB ModulationConventional RGB Modulation
R
G
B
R’
G’
B’
Multiply
Multiply
Multiply
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Problem with RGB ModulationProblem with RGB Modulation
Overwhelming majority of pixels in the output raster will have a darker colour than original.
Better than value replacement.
Colours are not “lost” but what happened to the yellow.
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Inspiration for SatValModInspiration for SatValMod
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SatValMod ConceptSatValMod ConceptLower Saturation
CutoffLower Value
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SatValMod MultipliersSatValMod MultipliersLower Saturation
Lower Value Cutoff
Value multiplier
Saturation multiplier
Shade value
Mul
tiplie
r
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SatValMod DetailSatValMod Detail
HH
SS
VV
R
G
B
*
* =
=
Pixel value in grey-scale imagedetermines multiplier
SmSm
VmVm
HSV2RGB
Multipliers
0.75
1.00
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SatValMod in ArcGISSatValMod in ArcGIS
SatValMod written in VBARuns in ArcGIS 8.x or 9.x (ArcMap – ArcView or ArcInfo)
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SatValMod Colour Raster OptionsSatValMod Colour Raster Options
CLR filepixel valueand RGB’s
RGB
8-bit image planes 3 separate 8-bit raster files
RGB
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SatValMod ParametersSatValMod Parameters
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SatValMod parameters (CutOff)SatValMod parameters (CutOff)
CutOff = 255 CutOff = 180 CutOff = 128
CutOff should be the maxima of the shade raster histogram. For shaded relief images, this is sin(Altitude).
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SatValMod parameters (Vmin)SatValMod parameters (Vmin)
Vmin = 0 Vmin = 0.3 Vmin = 0.6
Vmin > 0 is best so shadows are not completely black.
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SatValMod parameters (Vexp)SatValMod parameters (Vexp)
Vexp = 0.3 Vexp = 1 Vexp = 3
Vexp 1 is recommended so shadows are not too extensive.
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SatValMod parameters (Smin)SatValMod parameters (Smin)
Smin = 0 Smin = 0.3 Smin = 0.6
Smin < 0.4 is recommended. Higher values do not provide enough decrease in saturation.
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SatValMod parameters (Sexp)SatValMod parameters (Sexp)
Sexp = 0.3 Sexp = 1 Sexp = 3
Sexp 1 provides better results
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Geology + Shaded relief aeromag.Geology + Shaded relief aeromag.
Value replacement SatValMod RGB Modulation
SatValMod doesnot lose or corrupt original colours.
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Pan sharpeningPan sharpening
Value replacement SatValMod RGB Modulation
Colour critical?Use SatValMod.
Sharpening critical,colour unimportant?Use value replacement
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Ternary imagesTernary images
Value replacement SatValMod RGB Modulation
U-Th-K RGB composite image integrated with shaded relief DEM
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ConclusionsConclusions
Value replacement SatValMod RGB Modulation
SatValMod provides better integration of colour and grey-scale imagery compared to many traditional methods.
Colour is more accurate.
SVM Parameters provide flexibility on integration.
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AvailabilityAvailability
• ArcGIS 8.x and 9.x MXD VBA • ArcMap
– ArcView or ArcInfo
• e-mail for download instructions
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