This page last changed on Jun 07, 2012 by bmmpxf.
The demo site referred to on this page is no longer maintained. This page is retained for historical purposes only.

Introduction

OpenPlans|http://openplans.org] has worked to stand up a demonstration of GeoServer's capabilities at http://sigma.openplans.org. It includes extensive data for all of the United States, and country outlines and named places for the rest of the world. We hope others will be inspired by it, and all our welcome to make use of our data and servers. We're not a commercial service, so we can not guarantee complete uptime, but we will try our best.

General

Why are you doing this?

OpenPlans is a high tech non-profit focused on enhancing citizen engagement and increasing government transparency. We believe that this kind of data should not just be legally available, but also more accessible. We also believe that citizens can collaborate with government, and we're hoping to experiment with bring the open source process of software to geospatial data, and to use this site as a basis for that. It also gives us an opportunity to test and refine GeoServer with large amounts of data.

What software did you use to make this?

All software used is completely open source. GeoServer is used for the mapping through WMS, and for access to the data through WFS. OpenLayers is used as the WMS front end, and some javascript code that we wrote is used for searching. TileCache is used to do the caching, which greatly improves performance. PostGIS on top of PostGresql is the backend database, and we highly recommend it.

What's in store for the future?

We're hoping to build out more functionality in GeoServer and show it off here. One of the things we're most excited to experiment with is user contributions. Both on the basemap layers themselves, and for new layers on top of it. See GeoCollaborator for more information, and Versioning WFS for our work on implementation using open standards.

Data

Where can I get the data?

All the data we used to create this map is available under the public domain, from three datasets - TIGER, VMAP0, and GNIS. The original datasets are all available under public domain. We've done some data cleaning and processing of each, to put them all in a PostGIS database that GeoServer can use. On the live site we are using the roads, landmarks, water and state outlines from TIGER, countries from VMAP0, and place names from GNIS.

We are working to make available the results of our data processing and cleaning, we'd like to put it out for download under a Creative Commons license. Email inquiry at openplans dot org for information. But in the meantime we've made tutorials and scripts on how to do the same loading process we did, follow the links for GNIS, TIGER, and VMAP0. You can also access the data from GeoServer directly through WFS, as GML or Shapefiles of a given area. Currently we limit access to 5000 features at a time.

Why just the US?

The big reason is that the US is one of the few countries where data is available completely free from proprietary licenses. The other reason is because we are based in the US, so it's an obvious target for us. We hope that in the future more data for the rest of the world will be available, and if you are standing up WMS servers of similar layers for other countries let us know, and we can include them in the map. And we can also help host it on our servers (but likely can't take the time to do all the processing and styling and the like).

Can I use your layers on my own servers?

Of course. Everything is released under an attribution share-alike creative commons license, so we ask that you give credit to OpenPlans - ideally our logo and a link to http://openplans.org. At the very least you are required to write somewhere on the page that you are using map layers from OpenPlans. If you would like to display layers without giving attribution just get in touch and we're likely happy to let you do so, we more just want to know where our maps are being used.

How can I make use of your layers?

The best way to use our layers is to use a client that follows the WMS Tiling Recommendation, though currently the only one we know about is OpenLayers. Any client that follows the recommendation will benefit from much greater speeds, and is much nicer because it puts much less of a load on our server. If you're wanting to expose our layers to a much wider audience, like WorldWind users, please talk to us so we can figure out a solution that will work.

To take advantage of the nice cache we're building up, point your OpenLayers or other WMS Tiling server to

http://sigma.openplans.org/tilecache-1.3/tilecache.cgi?

with the layer named 'sigma'.

wms_sigma = new OpenLayers.Layer.WMS( "TIGER", "http://sigma.openplans.org/tilecache-1.3/tilecache.cgi?", {layers: 'sigma' }, {numZoomLevels: 17});

This is a png layer, with transparency, so you can overlay on other maps. If you'd like gif rendering of the same (useful for ie6 and below when you want to overlay) then you can use the 'sigma-gif' layer.

Note that the tilecache link will only respond to WMS requests that are formed properly. If you'd like to hit the full WMS then contact us. But really, we just highly encourage to get your WMS client up on the Tiling recommendation.

Can I change the styles of your layers?

Yes, one of the benefits of open standards and open data is you can let others do fun things with your map. So you can make whatever crazy style you like, make an SLD file of it, and then send the request to GeoServer with the SLD, and it will render it as you want to see the map, not as some other random person thought you'd like to see it.

Troubleshooting

Why are things sometimes labeled too many times?

This is a result of combining our more traditional rendering with the more advanced (and faster performing) method of caching tiles and displaying those. We are working to improve GeoServer to render tiles specifically, so that labels won't be replicated in every tile.

Why does it sometimes take longer to load, especially when zoomed in?

In order to have nice speeds we've pre-cached a good portion of the map, meaning that we've already had GeoServer generate the tiles. We're slowly adding more, but when you look at a new area of the map you are actually helping to increase the speed for others who may look at the area. Google Maps pre-processes every tile before they put it out, while we go for a more iterative approach - first caching a portion, but then just building the cache as people browse to new areas of the map. This has the nice effect of caching the most popular areas over time, and not wasting processing power on high zooms in the middle of the ocean.

Why do I sometimes get 'Sorry, no data'?

There are several reasons that you might get tiles that say they have no data. If you're going to an area of the map that has not been cached and GeoServer is down then it won't be able to generate the data. TileCache also occasionally gets hit, and if it is not working properly you can also get no data messages.

Why is Internet Explorer 7 preferred over IE 6?

IE 7 contains a fix that makes our maps look much nicer. Before version 7 there was no transparency available for PNGs. Since these really don't work on IE 6 or below we decided to return GIF files instead. These can be transparent, but they don't look nearly as good. And we are also doing less pre-caching of them, since PNG's look so much nicer.

All other browsers work fine with PNG transparency, and a majority of our users are on firefox. IE6 really is not that great of a browser, so we recommend IE7 or Firefox.

Contact

How do I contact you?

Send an email to inquiry (at) openplans (dot) org.

Document generated by Confluence on May 14, 2014 23:00