The Feathering
tab (pictured below) allows the user to feather-blend selected overlay(s)
with the underlying overlay(s) on specified edges. This can be extremely
powerful tool for blending imagery/ maps from different sources and/or
at different resolution to make the edge between the map sets invisible.
Choose to either feather-blend around the edges of selected
files or along the boundary of one or more selected polygons. Feather
blending can be used on both raster (imagery) layers as well as gridded
elevation layers.
For elevation layers, feather blending works by calculating modified elevation values based on elevation value in the blended layer and the topmost elevation layer underneath the blended layer in the draw order.
Note: Exported data will preserve the feathering displayed in the map view. Global Mapper v20.1 and later will preserve feathering of image layers with more than 3 bands.
Note: To recreate the polygon from a previously feathered layer, choose the tool Save Feather and Crop Polygons to Layer from, the Favorites List in Favorites Toolbar and use the 
run button to create the polygon layer.
Example
The example below displays the results of feather-blending a very high resolution data set (0.15 meters per pixel) with a lower resolution (3.5 meters per pixel) dataset to remove the edge. Note that the higher resolution image has been purposely tinted violet to make the effect more obvious.
