The NPMap Symbol Library is the National Park Service’s web map icon set. We integrate these icons into our other mapping tools, including Park Tiles, Places, and NPMap.js/NPMap Builder.
The latest version is 2.3.0. It was released on May 2, 2017.
A graphic tradition
Symbol Library has a clear and distinctive graphic identity that is based on the map symbols developed by the Harpers Ferry Center for its print brochure maps. Each of the icons has been carefully adapted to address legibility and accessibility needs specific to the web. This attention to detail helps us provide a clear window into the large number of amenities, services, and attractions offered by our national parks.
Adapted for the web
We considered the following factors when adapting print map symbols for use on our web maps:
- Web map symbols need a slim profile to reduce bulk at multiple zoom levels, render well within placemarkers, and not interfere with other classes of information. As a result, we've eliminated the bounding box for our symbols.
- Supporting black, off-white, and white versions of each assures we can render them clearly on top of a wide range of base maps and placemarkers.
- Six sizes have been designed for each symbol for greater cartographic flexibility—three stand-alone symbol sizes (14, 22, and 30px) and three for placement within placemarkers (12, 18, and 24px).
- We use the Maki toolset built by Mapbox to adapt our symbols for use in NPMap Builder as placemarkers.
Every pixel counts
When optimizing artwork that varies in size from 30px square for our largest stand-alone symbol size to as small as 9px square for our 12px placemarkers, every pixel counts. We create our artwork to be as "pixel-perfect" as possible. In other words, we respect the pixel grid to make sure our symbols do not appear "fuzzy" on standard-resolution displays.
All our symbols are developed as resolution-independent scalable vector graphics (SVGs). Small SVGs that are not aligned to the pixel grid and/or optimized for their pixel dimensions fall apart, as their details are smaller than the pixels available to render them on screen:
Our modified sailing symbol provides an example of artwork that remains legible at the scale of pixels.
Screen capture of enlarged vector artwork:
Enlarged vector artwork in Pixel Preview mode:
Artwork at actual size:
A frequently-revised resource
We welcome your feedback on current symbols and suggestions for additional symbols. As new symbols are designed, we will bundle them into new releases of the library. Visit the Github repository to:
- Access source image files (formats available include SVGs and portable network graphics—PNGs—at standard and retina resolutions)
- Provide feedback and request new symbols via the issue tracker
Our commitment to developing quality map symbols is driven by our larger pursuit to set the standard in web cartography. All of our maps are built with carefully considered symbolization that represents our parks in a way other web maps simply do not or cannot. That said, like most of our other tools, Symbol Library is available under a liberal open source license so others can build on top of and learn from our work.