Layer Visibility

Adjusting the absolute visibility of a map layer is done in the Legend panel by checking and unchecking the boxes that appear beside each layer. Finer visibility adjustments can be accomplished in the Visibility sub-category. In this dialog box transparency and scaled visibility can be addressed.

By setting the minimum and maximum scale values the user can control at what mapping scale a layer will become visible. This can be an extremely beneficial tool for map layers which represent detailed features which would be lost, or create unnecessary clutter at certain scales. When an area on the map is zoomed to a particular scale within the threshold values assigned to the layer, the symbology will automatically appear. This can be useful for line coverages, such as roads or unfilled polygons, as well as labels and point features.

Since most maps are composed of a series of layers, each representing unique spatial information, it is often important to visualize underlying features for a complete picture of the area. Transparency of the entire layer can be addressed in the 'Visibility' sub-category by chosing the 'Transparent paint' option and using the slider bar to select the desired transparency (0 = clear and 100 = solid). By clicking 'Apply' the changes are immediately updated in the Map Viewer so the exact appearance can be chosen before the 'Layer properties' dialog box is closed. If the transparency of individual symbols or individual layers of symbols are modified, the total transparency of the layer is a product of all transparencies. This is more apparent when individual symbol adjustments are explained in more detail below.

Opaque paint means that no transparency adjustments are made to the visibility of the entire map layer. If the individual symbols and symbol layers have been modified, then the symbols are displayed on the layer with a defined transparency however, the entire layer is drawn with no further transparency adjustments. Simply, if no detailed symbol adjustments have been made and 'Opaque paint' is chosen, the entire layer will be drawn with solid colours. This option controls how the entire map layer is drawn in the Map Viewer. If further transparency adjustments are required to see features beneath the layer 'Transparent paint' should be selected but if the layer is behaving as it should, 'Opaque paint' should be chosen to ensure no further transparency adjustments. (Opaque = 100 transparency)

The erasing paint option is a rarely used but sometimes important option available in Patchworks. This option, would apply to a dynamic layer where not all features of the layer were classified to a specific symbol. For example, if the optimization model is running and attempting to locate the best blocks for treatment it will display the treatment at the time it is being considered, however if the model changes its mind regarding the location of that treatment it will not be removed. This problem is solved by using 'Erasing paint', however setting up the theme involves further customization in the PIN file (see the section called “The PIN file”). I'm concerned this needs more explanation or 'expert' explaination!