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Image Layers

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ImageLayers are one of the fundamental data types in Openwind. The difference between an image and a raster in Openwind is that an image is purely for display purposes. It can have no recognized meaning with the one exception that it may influence the validity of its parent through a pixel color test.

Openwind users may take advantage of conversion tools in Openwind to convert Image layers into much more useful RasterLayers.

For images derived from scanned paper maps or orthophotos, the options in figure 74 allow scaling of color channels, saturation, hue, or luminosity values into numeric values as the basis of a raster layer.

For false color images containing a key, users can go to the tab shown in figure 75 to convert to numeric values.

 

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Figure 74:   ImageLayer Properties: Image=>Raster Tab (1)

 

 

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Figure 75:   ImageLayer Properties: Image=>Raster Tab (2)

 

Image 082E_lc_1.tif has been downloaded from a database of Canadian satellite images processed into distinct classes of land-cover (EOSD - http://www4.saforah.org/eosdlcp/nts_prov.html). The key to this image was downloaded with the image and is shown in figure 76.

 

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Figure 76:   Example of an Image Key

 

By using the key given in figure 76, one can create a scheme in Openwind to convert the pixel colors in the image to numeric values representing either roughness or vegetation height. Once input, the image key can be saved for later use by choosing Save Color Profile. Openwind does not save these values internally so they should be saved as a color profile (*.cfg) file if they are likely to be useful in the future.

It is assumed that the images come with coordinate information or the user has access to GIS resources in order to geo-reference images. In order to correctly load an image into Openwind, users must have the north, south, east and west extents of the image in either UTM or geographic coordinates. Images in geographic coordinates will be resampled in a manner similar to geographic rasters.

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