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Saturation And Value Modulation: A New Method For Integrating Colour And Grey-Scale Imagery

Saturation And Value Modulation: A New Method For Integrating Colour And Grey-Scale Imagery. David Viljoen & Jeff Harris Geological Survey of Canada. Overview. Why integrate colour and grey-scale data? Conventional methods and problems.

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Saturation And Value Modulation: A New Method For Integrating Colour And Grey-Scale Imagery

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  1. Saturation And Value Modulation: A New Method For Integrating Colour And Grey-Scale Imagery David Viljoen & Jeff Harris Geological Survey of Canada 1/30

  2. Overview • Why integrate colour and grey-scale data? • Conventional methods and problems. • Saturation-Value-Modulation concept & SatValMod ArcGIS implementation. • Geoscience examples. 2/30

  3. Integrating Colour & Grey-scale imagery Enhancing the visualization of a dataset. } DEM with shaded relief of DEM for Mt. Logan 3/30

  4. Integrating Colour & Grey-scale imagery Visualizing the relationships between two datasets. } K-Th-U (RGB) Gamma ray spectrometer with Landsat TM 7 4/30

  5. Layer transparency 20% 40% Result is independentof layer order Transparency of Colour (Colour over shaded relief) 60% 80% 60% 80% Transparency of shaded relief (Shaded relief over colour) 40% Layer transparency control in ArcMap 20% 5/30

  6. Red-Green-Blue coordinates RGB used to define colours in computers and image files. Integrating colour and grey scale imagery involves manipulation of colours in RGB & HSV coordinate spaces. 6/30

  7. Hue–Sat–Value coordinates Saturation Hue V = 100 100 120º 0 Value 0º S = 100 100 240º 0 0º 359º Hue 7/30

  8. R R H G G S B B V Conventional Value Replacement RGB2HSV HSV2RGB STOP 8/30

  9. Problems with Value Replacement • Loss/corruption of colour where: • Pixel colour is differentiated on Value (HSV) • Pixel colour has low saturation (achromatic axis of RGB cube) 9/30

  10. Problems with Value Replacement 1. Pixel colour is differentiated on Value Replace V with pixel values from shaded relief 10/30

  11. Problems with Value Replacement • Pixel colour has low saturation (achromatic axis of RGB cube) … to replace the Values of colours with low saturation … Using Values from grey-scale image … … results in poor image integration. 11/30

  12. R R’ G G’ B B’ Conventional RGB Modulation Multiply Multiply Multiply 12/30

  13. Problem 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. 13/30

  14. Inspiration for SatValMod 14/30

  15. SatValMod Concept Lower Saturation Cutoff Lower Value 15/30

  16. SatValMod Multipliers Lower Saturation Saturation multiplier Multiplier Value multiplier Shade value Cutoff Lower Value 16/30

  17. R G S B V SatValMod Detail H Multipliers 1.00 = * Sm HSV2RGB 0.75 = * Vm Pixel value in grey-scale image determines multiplier 17/30

  18. SatValMod in ArcGIS SatValMod written in VBA Runs in ArcGIS 8.x or 9.x (ArcMap – ArcView or ArcInfo) 18/30

  19. R R G G B B 3 separate 8-bit raster files 8-bit image planes SatValMod Colour Raster Options CLR file pixel valueand RGB’s 19/30

  20. SatValMod Parameters 20/30

  21. 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). 21/30

  22. SatValMod parameters (Vmin) Vmin = 0 Vmin = 0.3 Vmin = 0.6 Vmin > 0 is best so shadows are not completely black. 22/30

  23. SatValMod parameters (Vexp) Vexp = 0.3 Vexp = 1 Vexp = 3 Vexp  1 is recommended so shadows are not too extensive. 23/30

  24. 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. 24/30

  25. SatValMod parameters (Sexp) Sexp = 0.3 Sexp = 1 Sexp = 3 Sexp  1 provides better results 25/30

  26. Geology + Shaded relief aeromag. SatValMod doesnot lose or corrupt original colours. Value replacement SatValMod RGB Modulation 26/30

  27. Pan sharpening Colour critical?Use SatValMod. Sharpening critical, colour unimportant? Use value replacement Value replacement SatValMod RGB Modulation 27/30

  28. Ternary images Value replacement SatValMod RGB Modulation U-Th-K RGB composite image integrated with shaded relief DEM 28/30

  29. Conclusions • 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. Value replacement SatValMod RGB Modulation 29/30

  30. Availability • ArcGIS 8.x and 9.x MXD VBA • ArcMap • ArcView or ArcInfo • e-mail for download instructions viljoen@nrcan.gc.ca 30/30

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