Given the world famous landscapes of Grand Canyon, Yosemite, and other National Parks, including shaded relief on Park Tiles was an easy decision to make. Trickier to decide was just how to design a shaded relief that could do justice to this spectacular terrain while also serving as an unobtrusive background for multi-purpose maps. Another objective was creating a relief that complements the design standards found on the visitor maps produced by Harpers Ferry Center.
On Park Tiles, the shaded relief functions as a ubiquitous background. The relief is kept light to maximize the legibility of park areas, roads, rivers, boundaries, urban areas, and labels that appear on top of it. A relief that prints too dark would lessen overall map legibility. We also wanted a color that could stand on its own as an attractive and pleasing tone — thus, sterile gray was ruled out. After trial and error, we decided on light, neutral beige.
A beige shaded relief makes it possible to present other map information lightly and with clear visual hierarchies. For example, roads appear unobtrusively in a light red. The shaded relief also features reduced contrast for its highlights and shadows. This makes for a less “noisy” background—the shaded relief does not distract from park and thematic information on the map. And because a little tone exists even the brightest highlights, white state and international boundaries show up no matter how rugged the terrain.
We’ve also paid close attention to water. Tones for land and water are complementary yet provide enough figure-ground contrast to distinguish the coast. River and lakes use the same blue tint as the oceans, putting all water features on the same visual plane. Even more important, the land-water boundary appears without any thin coastal lines, making for a cleaner map. A feathered vignette applies darker blue tones along the immediate coast fading to lighter blue further offshore. This graphical effect gives emphasis to coasts without excessively darkening the map.
Creating the shaded relief and ocean vignettes was accomplished with a combination of GIS and graphical software. For example, coloring the shaded relief as beige and adding ocean vignettes occurred in Adobe Photoshop using the Geographic Imager plugin by Avenza, which maintains georeferencing. We used Natural Scene Designer 6.0 to generate the shaded reliefs, saved as GeoTIFFs. To get around the 4GB file size limit for GeoTIFFs, we created smaller, overlapping shaded reliefs for the very large areas covered by zoom levels 9 and higher. We then used GDAL VRT files to reference the multiple GeoTiffs, and then loaded these single pieces into TileMill, giving these relief pieces a seamless appearance on the final online map.
For detailed information on creating web map shaded relief, visit http://www.shadedrelief.com/web_relief.