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Online cartography for richly layered maps

Several recent items have called attention to the growing effort to make really good-looking maps online – see Matt Ball on the coming “cartographic explosion” and Peter Batty’s posts highlighting the great maps from OSM and CloudMade and of course Stamen Design (hardly an inclusive list, but it’s already a long-ish intro sentence).

It’s an exciting time for all that.  We’re hopefully moving well beyond the ubiquitous pushpins of more map mashups than we can count (no dig against Google Maps, but the pushpins can get a bit old — see EveryBlock’s insightful post about “Google Maps fatigue” and FortiusOne’s original — and on-the-mark — blog title “Moving Past Pushpins“). 

From what I can see, however, most of the latest online cartography efforts are focused on road-centric basemaps.  This is great, but there’s a lot more mapped information out there that eventually will be either layered on top of these basemaps or provided online directly.  And we’ll need good cartography to display richly layered online maps effectively.

I wanted to add a note about our humble contribution to that effort.  Our team at the City University of New York (and earlier at the Community Mapping Assistance Project, CMAP) has maintained an online mapping platform for the New York area since early 2001 called OASIS — the Open Accessible Space Information System.  OASIS displays open space resources (broadly defined) to help sustain these resources and visualize the nexus between community greening and broader urban planning issues.  The project is guided by a collaborative partnership of almost 60 greening groups, educators, individuals, businesses, nonprofits, and public agencies.


We recently completely revamped the website (see above screen shot).  The old site is at www.oasisnyc.net.  The new one is at http://www.urbanresearchmaps.org/oasis/map.aspx (best viewed in Firefox but tested in IE 6 & 7, Chrome, and Safari).  Our cartographic challenge — as Christy Spielman, a long-time colleague who helped create the original version of OASIS, noted — was to create an interactive map that certainly included transportation features, but in a way that kept them in the background while emphasizing parks, gardens, housing, land use patterns, zoning, schools, and more – plus aerial imagery.

Also, the recent upgrade includes neat new data such as local environmental stewardship “turfs” (in partnership with the USDA Forest Service) and *very* historical imagery and data from the Wildlife Conservation Society’s Mannahatta Project — photorealistic imagery of Manhattan circa 1609 as well as layers representing eco-systems, soils, Native American trails, and the 1609 Manhattan shoreline (more on Mannahatta in a separate post — it’s an amazing project). 


So we needed to figure out styles and colors and scale dependency that would work together (we have easily more than 4 dozen layers with distinct map styles), allow room for more layers of data in the future, and potentially be able to integrate data feeds and user generated data on the fly.

I think we did ok, though there’s always room for improvement (feedback is welcome!).  Christy (and I, though to a lesser extent) spent many hours developing color styles and symbology to find the right ones that worked well together.  We used ArcGIS to develop the maps (we’re most familiar with that, and it was quicker than having to learn SLD customization, for example).  We relied heavily on ColorBrewer, an amazing resource for GIS color symbology. 

ESRI’s New York City office — in particular, Patrick Gahagan – also helped us by providing ArcGIS techniques to create the map of subway stations and routes, and providing a DEM mosaic that we used as a backdrop for the new OASIS map.


Cached tiles were key, but deciding which layers to cache and which ones to be dynamic was an involved process.  We wanted to preserve as much flexibility for the map user while of course trying to speed up performance.  We ended up caching most of the transportation data (with the option to turn on/off the entire transporation cache layer) as well as the land use information – lot boundaries, building footprints, and parcel-by-parcel color shading. 


The parcel and building footprint layers were the most cumbersome as dynamic layers, each of them with literally a million features, so the performance gain by caching them was huge.  But Dave Burgoon (who coded the site from top to bottom – more on his impressive work in a separate post) customized the “land use” section of the legend to enable our users to display either the entire cached land use layer or to display each land use category dynamically (see screen shot below). 


This was a good compromise between performance (showing all land use patterns at all scales) and user flexibility (showing one land use category at a time dynamically isn’t too slow, and enables people to see all the commercial property versus residential versus industrial at a time).

The tiles, btw, were generated with ArcGIS Server and integrated into the map directly via OpenLayers.

We also took a page from the O’Reilly book “Designing Web Interfaces” plus Axismaps (who helped design GeoCommons Maker!) plus MapTube – and created a “dynamic transparency” tool that can accomodate each map layer on OASIS. 


The ExtJS transparency tool allows for a smooth, real-time transition as you slide from fully opaque to 100% transparent.  It makes for a powerful user experience.  The relevant quote from Designing Web Interfaces

Things move smoothly in the real world.  They do not “pop up”.  Transitions smooth out the jarring world of the Web, making changes appear more natural. (p. 233)

… and from Axismaps:

The transparency control lets mapmakers decide what works and what doesn’t.

Hopefully the cartographic result works well.  We’d love to know what you think!

3 Responses

  1. […] in New York City — see “A new OASIS for New York“.  (Also see an earlier blog post about how we designed the cartography in the new OASIS […]

  2. […] we decided on different GIS technologies/techniques for the Long Island Index mapping site.  And an earlier blog post discusses our cartographic decision-making for the new OASIS […]

  3. […] own style that didn’t conflict with other thematic layers and choropleth overlays, either we rolled our own.  Or if we used Google Maps, we used the Flash API so we’d have the ability to desaturate […]

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