Map GPS Coordinates - GPS Map Coordinates ... - Global Mapper

The Transparent option allows a particular color (or colors) to be displayed transparently, making it possible
to see through a layer to the layers underneath. For example, when viewing a DRG on top of a DOQ, making
the white in the DRG transparent makes it possible to see much of the DOQ underneath. Pressing the Set
Transparent Color... button allows the user to select the color (or multiple colors for palette-based files) to
treat as transparent in the selected overlay(s) as well as save the palette for palette-based files to a color palette
(.pal) file. If you also check the Make Very Similar Colors Transparent as Well option, any colors that are a
very similar color to the selected transparent color will also be displayed transparently. This is useful for
getting rid of colors in lossy formats like JPG and ECW where the colors are not exact.
The Resampling option allows you to control how the color value for each displayed/export location is
determined based on the values in the file. The following resampling methods are supported:
• Nearest Neighbor - simply uses the value of the sample/pixel that a sample location is in. When
resampling or reprojected an image this can result in a stair-step effect, but will maintain exactly the
original color values of the source image.
• Bilinear Interpolation - determines the value of a new pixel based on a weighted average of the 4
pixels in the nearest 2 x 2 neighborhood of the pixel in the original image. The averaging has an
anti-aliasing effect and therefore produces relatively smooth edges with hardly any jaggies.
• Bicubic Interpolation - a more sophisticated method that produces smoother edges than bilinear
interpolation. Here, a new pixel is a bicubic function using 16 pixels in the nearest 4 x 4 neighborhood
of the pixel in the original image. This is the method most commonly used by image editing software,
printer drivers and many digital cameras for resampling images.
• Box Average (3x3, 4x4, 5x5, and 7x7) - the box average methods simply find the average values of the
nearest 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), or 49 (for 7x7) pixels and use that as the value of the
sample location. These methods are very good for resampling data at lower resolutions. The lower the
resolution of your export is as compared to the original, the larger "box" size you should use.
• Box Maximum (3x3, 4x4, and 5x5) - the box maximum methods simply find the maximum value of
the nearest 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), or 49 (for 7x7) pixels and use that as the value of
the sample location. These methods are very good for resampling elevation data at lower resolutions
so that your new terrain surface has the maximum elevation value rather than the average (good for
terrain avoidance). This method behaves the same as the average on raster/imagery layers. The lower
the resolution of your export is as compared to the original, the larger "box" size you should use.
The Texture Map option allows a 2D raster overlay to be draped over loaded 3D elevation overlays. Selecting
the check box causes the overlay to use any available data from underlying elevation layers to determine how
to color the DRG or DOQ. The result is a shaded relief map.
Color/Contrast Adjustment Tab
Global Mapper User's Manual
The Color/Contrast Adjustment tab (pictured below) allows you to control the color balance and contrast of
the selected overlay(s).
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