Acetate: A Technical Introduction – part 1

*Note: this is a cross post from our developer blog: http://developer.geoiq.com/blog/

What is Acetate?

This week we launched Acetate a collaboration between us, Stamen , and 41 Latitude which allows users to create more compelling maps in GeoCommons by essentially re-ordering the basemaps to incorporate their own layers. This allows users to places their own data within the the basemap, creating a more visually pleasing effect and making maps easier to understand.

The goal of this post is to introduce you to the technical concepts of Acetate. I’ll start by providing a high-level introduction to the software and data we used to create and serve the maps, and then I’ll dive into how to use Acetate within GeoCommons.

It’s worth mentioning that this post is only the beginning of our look at the technical pieces of Acetate. In the coming days/weeks I’ll be writing a series of detailed posts on the various pieces that make up Acetate. So stay tuned!

Software and Data

As was mentioned in other introductions to Acetate the software and data stack we’ve used is all open source as is the entire Acetate project (Acetate on Github). The software used in Acetate centers on using Tilestache to render and serve map tiles. Tilestache relies heavily upon both Mapnik (to style data) and PostGIS (to store data). I’ll be diving into the details on installing and configuring those pieces in a follow up post to this coming very soon.

The majority of the data used in Acetate is from OpenStreetMap, Natural Earth , and NASA’s SRTM data. Each dataset are tied together with a series very nice stylesheets designed by Stamen and are served as map tiles via Tilestache. Again, more on the details of these in a later post.

Acetate Layers

The general idea behind Acetate is that it’s a basemap in the same vein as OpenStreetMap, Google, Microsoft, Yahoo, and MapQuest, but it separates itself by providing several independently accessible layers. Each layer is described below.

Acetate Roads:

The Acetate Roads layer is a very light-weight layer with only roads on a transparent background. This layer is “sortable” and can be placed over/under other datasets within maps.

Acetate Place Names:

The Acetate Place Names layer is another sortable layer that allows you make your maps much more clear by being able to place map labels on top of all dataset layers in your maps.

Acetate Hillshade:

The hillshade layer is the base layer used in the Acetate Terrain layer (see below) and is generated from NASA’s SRTM Digital Elevation Model (DEM).

Acetate Background:

The Acetate Background layer is general basemap used in Acetate. It’s free of all labels in order to keep it very light-weight and simple.

Acetate Terrain:

This layer is a composite layer, meaning it combines two or more layers together. For the Acetate Terrain layer we’ve combined the Acetate Background with the Acetate Hillshade layer to create a more visually pleasing basemap.

Acetate:

And finally we have the full composite basemap (not currently used in GeoCommons). This layer uses each of the above layers (except the hillshade and terrain) to form a fully functioning basemap with roads and place name labels.

Using Acetate in GeoCommons

If you go to GeoCommons right now and make a map you’ll notice that Acetate is now the default background map in all new maps. In the layers “palette” (the list of layers in the upper right hand corner of the map) there are two “injected” layers: Roads and Place Names. These layers are the movable components within Acetate meaning that your map layers can be re-ordered and shuffled with respect to these two layers.

This is a before and after of the layer re-ordering with Acetate layers.

You can see that map layers can be re-ordered to create different effects. Roads and labels can be placed above or below your own data layers. If you’d like to try re-ordering some layers is map available for you to edit and play around with:
http://geocommons.com/maps/46555/edit

In addition to re-ordering and placing layers between Place Names and Roads you can also change the underlying basemap to be the new Acetate Terrain layer. To do this follow these steps:

Step 1. While in “edit mode” in your map select the “Basemap” button near the top right corner. The Basemap palette will appear in the upper left corner of the map.

Step 2. In the Basemap palette select the terrain icon and choose the Acetate option from the list. The underlying basemap will then change to the Acetate Terrain layer. In the screenshots below you can see the before and after effect:

Before adding Terrain:

After adding Terrain:

And that’s it! You can try experimenting with different layer styles and types and see how Acetate can make really great maps! If you’re curious to see some examples of maps that have been created with Acetate so far this link. If you want to share what you’ve done with Acetate you can add an ‘acetate’ tag to your map and share it the world.

Next time:

In my post on Acetate I’ll dive deeper into the software and data we’ve used in Acetate. I’ll go through the details of installing Tilestache, getting your own database rolled out, and how to get started with the Acetate code base.