Crater Lake National Park

NPMap

Digital maps for the National Park Service

The Anatomy of Park Tiles

Posted on 24 Jan 2013 by Mamata Akella

In a previous post, we introduced you to Park Tiles, an online basemap we are working on. In this post, we'll go into more detail about how we're serving Park Tiles and outline how you can use the basemap in your own web maps.

Background

We've all seen the traditional mash-up pattern where data are placed on top of a basemap and, in turn, obscure the underlying (and important!) contextual information. Most “traditional” online basemaps used in web map applications have been designed for navigation first and foremost. Because of this, these basemaps tend to be information rich with a wide variety of highly-saturated colors to denote different road, landuse, and landcover types. The problem with these traditional designs is that information mashed-up with them doesn't always pop off the map and often gets lost. As the use of basemaps as backdrops for spatial information changes, the way these basemaps are designed and served needs to change as well.

Basemaps available through various providers are shifting towards a more minimalist and subdued style where a better figure-ground relationship is established between the basemap and the mashed-up content. This isn't a new idea. It is something print cartographers have done for years. For example, in a National Geographic Atlas, you don't see bird migration data on top of a road map with all of the reference information covered up. You, rather, see these data overlaid on a map background that supports the information instead of distracting from it.

As described in our introductory blog post, the design of Park Tiles is a subtle one. The shaded relief on the basemap is colored to make it sit nicely in the background and the other reference information is equally subdued. The features that are highest in the visual hierarchy are National Park units and their labels. This design ensures that Parks are clearly visible and information that is mashed up on the basemap comes to the foreground (if designed appropriately).

Another pattern that has emerged over the past few years is a change in the way basemaps are served. More and more, we're seeing basemaps that are separated into various components. Some examples include Esri's Terrain with Labels and Light Gray Canvas Map. Both of these maps gives users the ability to put reference information that is typically underneath mashed-up content on top. MapBox's suite of basemaps goes one step further, giving users the ablility to reorder layers, turn groups of features on and off, and recolor groups of features dynamically. With the release of their new basemap designs, Stamen has also created a reference overlay from their Toner style that can be used to provide geographic context with other basemaps. Two of the first online basemaps to demonstrate these new patterns were Esri's Terrain with Labels (released in 2009) and GeoIQ's Acetate basemap (released in 2011).

Our Idea

We have been thinking about how we can take this pattern one step further. We have decided to “explode” Park Tiles into multiple layers. What this means is that each feature on the map is served on its own.

We decided to do this for a few reasons:

  1. We want to support multiple overlay types - including points, lines, and discontinuous/continuous polygons.
  2. We want to get the greatest amount of flexibility out of our basemap so we can mix and match layers to support any number of projects and applications.
  3. We feel like this is new pattern is worth exploring.

Take a Look

You can use our Park Tiles Viewer to explore this pattern in more detail. In the bottom right-hand corner of the map, click the "Toggle Layer View" button.

Under the Overlays layer section, you will find two pre-generated overlay examples that are discussed in more detail below.

Overlay Types

Here are some examples of how this pattern works with line and continuous polygon data:

National Trails (Lines)

We want our National Trails data to be shown over Parks and water features, but, as seen in the image below, we don't want them to overrun labels for Parks, cities, and hydro features.

Default Trails

In this case, we can put the tiles for our National Trails underneath the tiles for Park, city, and hydro labels.

Reordered Trails

Ammonium Deposition in Parks (Continuous Polygons)

The traditional mash-up pattern is to overlay contiguous data on top of a basemap while using transparency to allow the underlying geographic context to be seen.

Default Mash-up

A more desirable view of the Ammonium Deposition overlay would be a view where the context (roads, labels, Park polygons, etc.) are on top. In this case, we would put the Ammonium Deposition tiles above the shaded relief but below all of the other reference information. The result can be seen in the image below.

Better Mash-up

The above example still has some issues. The urban areas (symbolized in a pale yellow) can be misinterpreted as data and it is difficult to see the variation in Ammonium Deposition in Rocky Mountain National Park because Park polygons are symbolized with a fill.

The solution is to turn off the urban area and symbolize Park polygons using outlines. This way, there is no other polygon data interfering with the continuous surface of Ammonium Deposition.

Ideal Mash-up

Flexibility

By serving Park Tiles as individual tilesets, we're giving ourselves the flexibility to use the individual components of the map for a variety of projects. For example, in some of the Park projects we work on, the focus of the map is only on a subset of Parks managed by the Park Service. In those cases, we would not serve our layer with all of the Parks displayed, but would instead create an alternative Park layer to display only the relevant Parks on the map. The number of use cases addressed by this basemap is huge. Each layer of the map can be mixed and matched into a variety of web maps, and each layer of the basemap can be ordered in a way that best tells the story of the overlaid data.

How to Use and Access Park Tiles

Whether or not you are a Park Service employee or partner, you may find our new basemap and the pattern we've implemented useful in some of your projects. If you'd like to learn more about how to access these tilesets and use them in your own applications, take a look at the Using Park Tiles tutorial in our support documentation.