Open Online Polygon Mapping Communities
A community needs to be created where one can create and represent polygons, similar to how people can edit line features with openstreetmap (OSM, . There are several efforts to allow people to create and manipulate polygons, which are currently being inventoried below.
There would be great power in an online community around polygons. For example, a user could enter a year, such as "1900" and see the way the world was then, as well as animate historical changes and events (see Centennia as an example, 1000 years of European history and 10,000 border changes ). Also, a community could exist around different statistics, such as population density, which could be visualized in darker shades of red (see Gridded Population of the World). I can then edit a map, changing and adding polygons, and their colors and metadata. I should also be able to view areas by, say, population density and other statistics.
List of Online Polygon Mapping Tools and Communities
There are several tools that are available to map polygons online, which range from proprietary, to semi-proprietary and based on open source tools, to completely open source. Most of the open source tools are built on functions that exist in OpenLayers.
- OpenLayers. Demo 
- OpenMoose. Demo . Uses OpenLayers.
- OpenStreetMap. An explanation of how to create polygons, such as buildings . A user closes a polygon by clicking the first point in a polygon to close it, then adding choosing from a dropdown menu a polygon feature such as "building".
Web Map Server - Time (WMS-T) is a standard that allows a WMS server to provide support to temporal requests. This is done by providing a TIME parameter with a time value in the request. Overview of projects using WMS-T: 
- GeoServer. Blog entry about WMS-T .
- MapServer. WMS-T page .
- GeoCommons . Communities can collaborate online around maps. Users can simply upload a spreadsheet with names of entities (countries, zip codes, etc), with associated numbers, and a map is automatically generated. Can upload KMLs, and see animations.
- Click2Map : Customers can buy the tools to put on their own servers. A free demo is online. Users can create a polygon, and a dialog pops up automatically, in which a user can easily add the metadata, including the name and color and line thickness and description.