DeLorme is justifiably proud of its pioneering endeavors in the field of digital mapping over the last 25 years. Those of us old enough to remember the early versions of Street Atlas USA® will recall the sense of amazement when we learned that virtually every road in the entire U.S. could fit onto one of those new-fangled CD ROMs. The basis for this amazing feat was the simple fact that all of the features on the map were efficiently stored in a database and rendered on the screen only when required. This vector-based approach to mapping is still the foundation of most of DeLorme’s software and data products, including the new World Base Map.
The delivery of maps in vector format offers several advantages over raster data products, such as aerial imagery or scanned paper maps:
The data is much smaller so a wider geographic coverage area can be delivered per megabyte of storage- The data is updatable so periodic edits and corrections are relatively straightforward
- The data display can be manipulated by the end user
XMap users have several customization options that can be utilized to create a base map that is tailored to the needs or requirements of the project at hand:
Map Features
The Map Features tab in the Option dialog (accessible from the toolbar) offers two levels of control depending on the degree of customization required.
The main window offers a concise list of map feature types that can be checked on or off as needed. This list includes points of interest, minor roads, and map grids.- By selecting the Use Custom Map Features option at the bottom of the window, the base map contents can be fine tuned to a greater degree. Individual types of lines, points, and polygons can be displayed or hidden using the appropriate check boxes. A common approach to map feature customization is to initially disable all objects in the base map by selecting the None button and then individually turning on the features that are needed.
Map Features settings are recorded in the current XMap project so it is possible to create template maps containing various combinations of features by creating and saving several projects.
Contour Display
In the topographic base map in XMap, contours are dynamically generated from the underlying digital elevation model. If required, the contours can be removed from the map using the Map Features settings as noted above. Alternatively, the interval or space between adjacent contours can be adjusted to accentuate the elevation in relatively flat terrain or to reduce the concentration of contour lines in mountainous areas. Note that the contour interval is automatically optimized at different zoom levels so it is usually not necessary to make manual adjustments.
If necessity dictates, the contour properties can be adjusted in the Map Data tab by expanding Reference Data, then expanding Topography and right-clicking on Contours. In the resulting window, the first setting allows the selection of Low Density, High Density, or Custom contour spacing as well as the selection of the zoom level at which contours first appear. If Custom is selected, the next window provides the opportunity to set the contour interval within specified zoom levels. It also offers the option to establish the major contours at each zoom level, which stipulates which contour lines are labeled on the map.
The next window in the Contour Properties dialog box offers the option to adjust the overall zoom level range for contours. The final window is used to select the map views in which the contours will be displayed.
Shaded Relief
The pattern of shaded relief or terrain shadow is employed by XMap to emphasize the topography and, as with contours, it is generated dynamically from the digital elevation model. The shaded relief pattern can be adjusted to imply an alternative light source position so the simulated shadow falls on a different side of each mountain or hill.
To make this adjustment, right-click Shaded Relief in the Map Data tab and click Properties. The first screen in the Shaded Relief Properties window has settings to change the sun bearing and inclination or angle above the horizon, as well as the brightness range for the shadow effect. As with the contour settings, the next screens provide the option to choose the zoom level range and map selection within which the shaded pattern will appear.
Map Colors
Under the Display section of XMap’s Options window, there are three Map Colors options. Topo Colors, the default setting displays all topographic features as well as land cover information; Street Colors mirrors the map view in DeLorme’s Street Atlas USA—with no contours, shaded relief, or land cover—for a simple street view; the High-Contrast Colors option renders the map with darkened features and is intended for in-vehicle use, especially when driving at night when the brightness of the screen can be distracting.
Magnification
Also contained within the Display Options window, the Magnification drop-down list can be used to alter the size of the features, text, and symbols on the map. The most common use is to increase the magnification so that objects appear larger and text is easier to read, especially on a small screen with a high screen resolution. Note that on the GPS tab in the Options dialog, a check box offers the option to automatically magnify the map when GPS tracking is enabled.
Layering
There are two ways to adjust the layering hierarchy on the map depending on whether the layer in question is raster or vector. By default, the layering sequence starts with base map vectors at the bottom followed by raster layers such as aerial imagery, and GIS and draw layers on top. Often it is necessary to display specific features from the base map on top of a raster or a GIS layer or to adjust the layering hierarchy of specific GIS layers.
To adjust raster layering, locate the layer in question in the Map Data tab and right-click to select Properties. If necessary, click Next to display the Data Positioning window and, using the drop-down list, select the feature class that you wish to display on top of the raster layer. Note that because of the hierarchical structure of the base map data, the chosen selection will also include those objects that appear above it in the list. For instance, if Roads is selected, Town Borders, Business POIs, etc, will also appear. If these additional features are not needed, they can be filtered using the Map Features settings noted above.
By default, this layering behavior will be applied to the selected data throughout its entire zoom level range; however, it is also possible to establish a different layering sequence for a specified zoom level range.
GIS layering is controlled from the Layering section of the GIS tab. As each new layer is imported or created, it is assigned a z-level value of 4500. By increasing or decreasing this value, the position of the selected layer can be moved up or down relative to other GIS layers or to features in the base map. The process of adjusting the layering can be performed by simply typing a new z-level value or by clicking and dragging a selected layer in the layering list and dropping it at the appropriate position in the hierarchy.
The inherent flexibility of XMap’s topographic base map means that it is possible to create a truly unique map view as a foundation for clearly representing and emphasizing user data layers.
