Common Raster Settings

File Type

The File Type section allows you to choose what type of file to generate. The various file types are described below:

• 8-bit Palette Image - This option generates a 256-color raster file with 8-bits per pixel. The Palette options described below will apply in this case.
  

• 24-bit RGB - This option generates a raster with 24-bits per pixel. Uncompressed images generated with this option will be at least 3 times the size of those generated with the 8-bit Palette option, but the colors in the image will exactly match what you see on the screen. You can also maintain the colors while achieving some compression using compression option.
  

• Multi-band - This option generates a raster file with 1 or more bands of data at either 8-, 16-, or 32-bits per band of data. This option is very useful when working with multi-spectral imagery with more than 3 bands of data, such as RGBI, Landsat imagery, or data sets with more than 8 bits per color channel. After selecting this option additional dialogs will be presented allowing for further setup of the multi-band export by choosing the input sources for each band in the output image.
  

• Black and White- This option generates a two color file with 1 bit per pixel. This will generate the smallest image of these options. However if the source image had more than two colors the resulting image will be very poor. By default, white will be a value of 0 and black will be a value of 1. This can be reversed by selecting the Grayscale - Min Is Black palette option.
  

• Elevation (16-bit integer samples) - This option generates an elevation grid using the currently loaded elevation grid data sets. Elevation samples will be stored as signed 16-bit integers.

• Elevation (32-bit integer samples) - This option generates an elevation grid using the currently loaded elevation grid data sets. Elevation samples will be stored as signed 32-bit integers. Check that vertical units are appropriate prior to using this option, intended for use with high resolution, sub-metric elevation data and values.

• Elevation (32-bit floating point samples) - This option generates an elevation grid using the currently loaded elevation grid data sets. Elevation samples will be stored as 32-bit floating point values.

Palette

When generating a 256 color (8-bits per pixel), it is necessary to select a palette indicating what 256 colors will be used to describe the image being exported.

The following choices of palette are available:

Sample Spacing

The Sample Spacing section allows the user to select the grid spacing to use when generating the file. The default value is the average of the grid spacings of all the currently loaded raster and elevation overlays.

If the Always Generate Square Pixels option is checked, the smaller of the specified x and y resolutions will be used for both the x and y resolution.

Selecting Always Generate Square Pixels ensures that the resultant image file will look good even in software that is not able to deal with pixels that aren't square.

To specify the spacing in units other than those of the currently selected view/ export projection, press the Click Here to Calculate Spacing in Other Units button.

Specify the X and Y spacing of the output pixels in any of the selected units. These pixel dimensions will be translated into the units of the display projection during export. The Use Current Screen Pixel Size button will update the X and Y values to the dimensions of the map display. Use Last Exported Sample Spacing will update the X and Y values to the most recent export resolution.

Metadata File Formats to Generate

Metadata File Formats to Generate

A range of accompanying metadata files can be generated upon export, to preserve spatial information that may not be contained in the export itself. Choose from the following Metadata file formats:

• World File (.bpw)
• PRJ (Projection)File
• ESRI .aux.xml Projection File
• ERS (ERMapper Header) File
• TAB (MapInfo) File
• MAP (OziExplorer) File
• MCF (ublox Position) File
• TXT (Text) Metadata

Resampling When the pixels change size due to changes in resolution or reprojection, the resampling method determines how new pixel values are calculated.

• Nearest Neighbor - simply uses the value of the sample/pixel that a sample location is in. When resampling 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 less stair-step effect.
• 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 (2x2, 3x3, 4x4, 5x5, 6x6, 7x7, 8x8, and 9x9) - the box average methods simply find the average values of the nearest 4 (for 2x2), 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), 49 (for 7x7), 64 (for 8x8), or 81 (for 9x9) ) 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.
• Filter/Noise/Median (2x2, 3x3, 4x4, 5x5, 6x6, 7x7, 8x8, and 9x9) - the Filter/Noise/Median methods simply find the median values of the nearest 4 (for 2x2), 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), 49 (for 7x7), 64 (for 8x8), or 81 (for 9x9) pixels and use that as the value of the sample location. This resampling function is useful for noisy rasters, so outlier pixels do not contribute to the kernel value. Some common sources of raster noise are previous compression artifacts or irregularities of a scanned map/image.
• Box Maximum (2x2, 3x3, 4x4, 5x5, 6x6, 7x7, 8x8, and 9x9) - the box maximum methods simply find the maximum value of the nearest 4 (for 2x2), 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), 49 (for 7x7), 64 (for 8x8), or 81 (for 9x9) 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 the new terrain surface has the maximum elevation value rather than the average (good for terrain avoidance). The lower the resolution of the export file is as compared to the original, the larger "box" size that should be used.
• Box Minimum (2x2, 3x3, 4x4, 5x5, 6x6, 7x7, 8x8, and 9x9) - the box minimum methods simply find the minimum value of the nearest 4 (for 2x2), 9 (for 3x3), 16 (for 4x4), 25 (for 5x5), 49 (for 7x7), 64 (for 8x8), or 81 (for 9x9) 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 the new terrain surface has the minimum elevation value rather than the average. The lower the resolution of the export file is as compared to the original, the larger "box" size that should be used. 
• Gaussian  Blur (3x3, 5x5, 7x7) - the Gaussian blur methods calculate the value to be displayed for each pixel based on the nearest 9 (for 3x3), 25 (for 5x5), or 49 (for 7x7) pixels. The calculated value uses the Gaussian formula that weights the values based on the distance to the reference pixel.

Other Options

Save Scale/Elevation Legend/Grid if Displayed

The distance scale, elevation legend, and coordinate grid will be saved to the file (except elevation grids) if they are configured to show up in the main display.  

Save Vector Data if Displayed

Any loaded vector data that is configured to show up in the main display will be saved to the file (except elevation grids).

Make Background (Void) Pixels Transparent:

Only some raster formats support transparency. Depending on the format, an alpha channel will be added to the created file to indicate which pixels should be treated as transparent, or a NoData value will be applied.

Tiling Panel

Export Bounds