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

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

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

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

5/30 Layer transparency 20% 40% 60% 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 independent of layer order

6/30 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.

7/30 Hue–Sat–Value coordinates Hue Value V = 100 S = 100 0º0º 120º 240º º0º 359º Saturation Hue

8/30 Conventional Value Replacement R G B H S V R G B RGB2HSVHSV2RGB STOP

9/30 Problems 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)

10/30 Problems with Value Replacement 1. Pixel colour is differentiated on Value R,G,BH,S,V 0,110,0120,99,43 0,188,0120,99,74 0,253,0120,99,99 Replace V with pixel values from shaded relief

11/30 Problems with Value Replacement 2.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.

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

13/30 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.

14/30 Inspiration for SatValMod

15/30 SatValMod Concept Lower Saturation Cutoff Lower Value

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

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

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

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

20/30 SatValMod Parameters

21/30 SatValMod parameters (CutOff) CutOff = 255CutOff = 180CutOff = 128 CutOff should be the maxima of the shade raster histogram. For shaded relief images, this is sin(Altitude).

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

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

24/30 SatValMod parameters (Smin) Smin = 0Smin = 0.3Smin = 0.6 Smin < 0.4 is recommended. Higher values do not provide enough decrease in saturation.

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

26/30 Geology + Shaded relief aeromag. Value replacementSatValModRGB Modulation SatValMod does not lose or corrupt original colours.

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

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

29/30 Conclusions Value replacementSatValModRGB 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.

30/30 Availability ArcGIS 8.x and 9.x MXD VBA ArcMap –ArcView or ArcInfo for download instructions