Cartography

Empirical vs. Theoretical

3D Stills | Cartography | GPS & Compass | Remote Sensing

Satellite imagery is empirical. An imaging satellite measures patterns of light waves bouncing off the surface or clouds. Computers automatically map basic ground cover types.

Pure theory attempts to map terrain and ecosystems using math and symbology. Simple cosine calculations map shaded relief during all seasons. Symbolic lodgepole pines and granite strata "fill" the proper regions. Such "virtual renderings" look realistic and achieve much because mathematical detail can be multiplied upon each symbol. Thus the light cast upon each pine needle matches the seasonal sun angle and sparkles with flash: thanks to geometry.

Pure theory must also calculate precisely where and how much to use each symbol on a given pixel representing the real world. Here, nature proves elusive. But theory continues to advance. Math ecology estimates ground cover based on the geometry of the terrain and "rules of nature:" Shady northern slopes tend to hold snow longer, for example. The computer will render snow and shade on northern aspect slopes, with sunny grass renders on southern aspect slopes. Simple math ecology breaks down without variables like wind speed and direction. Windpacked snow might endure on south slopes, and so forth. Likewise, trees certainly prefer particular micro-climates, but many individual trees grow outside their ideal setting. Theory fails to adjust for factors like animal and wind dispersion of plant seeds. Theory also can not predict the locations of roads and clear cuts.

Thus combinations of empirical remote sensing data and detail rich final virtual renderings make the most of both advances in cartography.

Color bands mark of ranges of elevation, such as every 1,000ft.

Generic graphic icon represents features at some map location. Symbols can represent points (trailhead) lines (4wd road) or areas (alpine areas) Symbols are cartographic shortcuts, drawing attention to complex meanings specifically located on the map but also generalizing the individual character of each feature such as a campground or tree. Virtual renders, for example may have libraries of 5 or 10 Ponderosa Pines. If lighting & size can me modified in 5 or 10 ways then suddenly hundreds of tree symbols are available. Such a quantity is enough to rapidly symbolize wide swaths of landscape with realistic patterns. A perfect depiction of a forest, however, requires thousands of unique tree symbols, since every tree on the ground is different.