One of the major projects we have kicked off over the past few months is an online National Park Service-styled basemap we are calling Park Tiles. In this blog post, I'll briefly discuss the design rationale behind Park Tiles and give a brief overview of the data and technology we are using to drive this project.
As more and more Park Service groups and partners move to the web, we've found a need for a customized NPS basemap that can be used as a backdrop to display the wide variety of spatial data that are collected and maintained by the service.
Currently, the NPS uses basemaps from various providers, including Bing, Esri, Google, and MapBox. For certain projects, however, we are looking for more stylistic control over these basemaps. Some of these providers allow us to modify colors and turn some layers on and off, but often when we mash up our content on these basemaps there is a lot of overlap and our information doesn't come to the foreground as much as we would like.
Park Tiles is not meant to be a total replacement for any of the basemaps we currently use. It is, rather, meant to give us an alternative basemap we can use in custom projects where we'd like to see our National Parks highlighted. We'd also like to incorporate more detailed park information (such as campsites, visitor centers, trails, etc.) at larger scales that can serve both NPS employees and visitors.
Most importantly, the National Park Service has a strong cartographic tradition that has been developed by the cartography team at the Harpers Ferry Center in West Virginia. Our primary goal with this online map is to transfer that tradition to the web. We are doing this by using NPS fonts, colors, and symbols. It is also important for us to maintain the graphic identity of the NPS so when we embed web maps in park pages, the maps compliment the existing style.
We have designed Park Tiles with a subdued style and a limited number of colors and information. As you can see below, the shaded relief and reference information on the map are designed using colors that are low in saturation. To contrast, the National Park points, polygons, and labels are symbolized and labeled using colors with higher saturation so they come to the foreground. We have limited the features displayed on the map knowing that if we need to add additional reference information, we have the freedom to do so. All of this has been done with the goal of clearly identifying National Park units and creating a basemap that can support multiple overlay types symbolized using a wide variey of colors.
The data we are using to build this map come from a variety of publicly available sources. The ScaleMaster diagram below shows the data source of each feature by zoom level (or scale). We are using data from the NPS at all scales for park units. Natural Earth data is used for reference information like administrative boundaries, administrative labels, roads, urban areas, and hydrography at small scales. We are using DEMs of varying resolutions for relief from NASA and the USGS.
At larger scales (zoom level 8 and above), we begin to switch data sources. Urban areas switch from Natural Earth to the US Census Bureau, coastlines are drawn from NOAA, and the majority of other features come from OpenStreetMap (OSM). Specifically, we are experimenting with OSM data at large scales to display features like points of interest, trails, and more detailed base data.
Larger scale designs (zoom level 10 and above) are still being prototyped. We prefer to use data from Parks, when available. In cases where individual Parks do not have data, we are currently exploring alternatives, particularly OSM.
We are using a combination of technologies to build and serve this map. To read in data from OSM we are using a couple of different approaches, including Imposm and osm2pgsql. Both of these tools allow us to manage and query OSM data using PostgreSQL and PostGIS. Park units are managed in a SQLite database, and the remainder of the data (for now) are managed in shapefiles.
The primary tool we are using to design Park Tiles is TileMill. TileMill is an open source design studio where multiple data formats can be read, queried, and styled. To create the shaded relief, we're using Natural Scene Designer and Photshop. For icons like highway shields and POI's (at larger scales), we are using Inkscape. We're also using some other tools, including Dymo for labeling and High Road to query and symbolize our road layers at zoom levels 8 and above.
Take a Tour
So far, Park Tiles is available for zoom levels 4-9. We're actively working on incorporating more zoom levels – we'll keep you updated!
You can view Park Tiles here. If you click on the "Switch" button, you'll see our initial large scale prototype of Mt. Rainier National Park that uses all OSM data.
Look for a follow-up blog post where we'll describe, in detail, how we are looking to serve our basemap.