Variable Opacity Merges

Select option from Overlay menu, Two map interactive comparison on  map. Merge two different maps. Put the overlays for map on separate map plane.

This option allows you to interactively merge two compatible maps, varying the opacity of the top image.  The two images must share the same image projection characteristics (UTM or geographic).  Possible data sets include:

• Imagery and DEM
• Two views of a DEM
• Two views of the same imagery (different contrast, filters, band combinations)
• Imagery from  two dates

To use this option:

• Open the two maps in separate windows.  Place any desired overlays.
• You must insure that the two images share the same projection characteristics (UTM or Lat/Long). 
• With the bottom image active, pick the Menu choice "Overlay menu, Two map interactive comparison, Variable Opaque merge".  The program will notify you if the two projections are not compatible.
• Pick the second map.
• The merge will be created, using the bottom image for the size and coverage limits.
• Use the slide bar to change the opacity settings.  See the images below for sample results.

Notes:

• Only request this product for the central region of the map, where the two products will overlap.
• Cannot move or resize the window.  If necessary, you must close the merge, select the new coverage limits, and then restart the opacity merge.
• If necessary, you can resample DEM as either DTED or UTM format, so it matches the imagery.

	Blend Value 255, seeing only the USGS DOQQ.
	Blend Value 200
	Blend Value 150
	Blend Value 100
	Blend Value 1, seeing only the USGS DRG

last Modification 9/16/2019