Hands On VGI is a specific example of the community-based information collection model that features content developed by end users. Amazon and Trip Advisor are familiar examples of sites that incorporate user community comments. These comments provide information from real consumers with direct knowledge of the subject and assist potential purchasers in making decisions. You are probably also already familiar with sites that promote geocollaboration and community mapping. Open Street Map and WikiMapia are examples of this type of site. These and other similar geocollaboration sites provide access to informal sources of data and local knowledge about the geography of a place. All sites that depend on user-generated content must motivate people to act voluntarily. Contributors need to understand how the content they collect supports the site’s overall goal. Also, sites that let end users enter information must be managed by an administrator to ensure that the content posted is credible, relevant, and not offensive in content or language and to avoid copyright infringement issues. When end users have been successfully motivated and are contributing to the map, administrators filter the map’s geometry to avoid clutter that could make the map illegible. For example, in places that have poorly detailed map coverage or out-of-date or expressive mapping, the rapid entry of information by the user community may result in maps that have overlapping shapes. Site administration is discussed more fully later in this article. Requirements for Building a VGI Site Using ArcGIS 10 Creating a VGI site requires not only assembling people and software but also designing a workflow, data schema, geodatabase, and map template. A discussion of these requirements follows. People The process of designing, constructing, implementing, and administering the site and implementing Web editing will require one or more GIS professionals with knowledge of ArcSDE, geodatabase design, and the use of ArcMap for Web map design and familiarity with publishing services using ArcGIS Server. One or more persons will also be needed to act as site administrators to maintain content credibility. Optionally, the role of the administrator can be limited to setting up a security policy for ensuring that the data is only accessed and/or edited by a select group of people. However, the most important factor to the success of the site is a user community willing to volunteer information. Required Software Components The Web application for collecting data should use ArcGIS 10 and one of the ArcGIS Web Mapping APIs that has been configured so all components for editing geographic data are enabled. The following components, configured as described here, are required when setting up a VGI site:  ArcSDE geodatabase containing features set up for handling Web edits  An ArcMap document that references one or more feature classes from an ArcSDE geodatabase  A feature template that defines the properties required for creating a new feature  The map document and its associated template, published as a map service with feature access  A Web application with UI controls for making edits to geometry and/or attributes Designing the Workflow of the ArcSDE Feature Class Schema Start by preparing the ArcSDE feature classes that will participate in the editing workflows. Keep in mind that the fields and their names (or aliases, if provided) will be visible to the end user of the editing application. Once the feature class has been added to ArcMap as a layer, table properties, such as alias name and visibility, can be tuned further. Please note that the order of the fields can only be defined in the feature class table, so they should be in the order you want the end user to see them in the Web application. Some other things to consider at this stage of data preparation include  Creating a separate geodatabase feature class to support Web editing if content also exists in the authoritative geodatabase  How you want the attribute data represented to users who may not be familiar with GIS?  Defining subtypes and domains (whenever possible) to simplify the attribute editing experience  Deciding if data can be registered as versioned or edited in a nonversioned environment (Feature classes that participate in nonsimple data types, such as topology or network data, must be registered as versioned.)  Configuring the feature class to support attachments in the geodatabase. (A feature class that has been configured to use attachments must be added to and published with the map document.) Preparing the ArcSDE Geodatabase When preparing the ArcSDE geodatabase, remember that all data that will be added to the map document for editing must come from a single ArcSDE geodatabase and must be registered with that geodatabase. Examine the database connection file to determine whether access to feature classes will be controlled using operating system authentication or database authentication. Defining Layer and Table Properties in ArcMap The feature symbology and layer names defined in the map document will be exposed to the Web application end user. Take great care to choose symbols that will be meaningful to non-GIS users and create aliases for all layers.  When designing the symbols that will be used when editing features, temporarily add the basemap layers that will also be used with the Web application so you can see how features will appear in the legend and on the map when the Web application is in use. In ArcMap, you can further modify how editable layers will appear in the Web application to end users.  Create aliases for all table fields exposed in the Web editing Continued on page 52 ArcUser Summer 2010 51 www.esri.com