icon and select the layer type.
Background layers including shape files, images, and rasters can be added in the Setup tree view. To add a new background layer, click on the icon and select the layer type.
Image area coordinates can be read from a world file or else specified by the user. If using a world file, the world file must be located in the same directory as the image file, with the same name. Otherwise, image coordinates can be entered by hand.
Shape file background layers require specification of a projection type. If a projection file (PRJ file) exists, the projection type is automatically read. Otherwise, a user-specified map projection must be selected.
The raster background layer is used when the user would like to use a digital elevation model (DEM) or other raster as a background layer in the Map view. Four raster formats can be selected:
· ESRI ASCII: a text file format, which requires that the coordinate system as well as the elevation unit are specified manually.
· dfs2: for a dfs2 raster file, the coordinate system and units are obtained from the file's metadata.
· GeoTIFF: a special format of tiff file, which also stores the coordinate system and units as metadata.
· ESRI binary grid: a binary format of raster, composed of multiple files with extension .adf. The raster is actually the folder containing the .adf files.
Background layers are displayed in the Map view in the order given in the list of layers found at the bottom of the tabular view (when Background layers is selected in the Setup tree view). The appearance of background layers follows the order in the list of images (i.e. the image in line 1 is on top, then image 2 is below image 1, then image 3 is below image 2, etc.). It is possible to rearrange the order of images by selecting an image and using the arrows to move the selected image up or down in the list.
Display settings for background layers can be modified in the Symbology tree view. In this view, layer transparency settings can be changed so that underlying background layers are visible in the Map view. It is also possible to remove layers from the map view by unchecking the Visible box. Other aspects of symbology can also be modified, such as colour schemes and feature labels. For more details about symbology options, please see the discussion of symbology in Section 2 (Working With MIKE HYDRO).
