Goal and Background
This lab is an introduction to VGI, or volunteered
geographic information. VGI is a crowdsourcing operation that allows the
general public to collect and upload geo-locations and their associated
attribute information to a web GIS application. This lab will teach someone how
to develop a web GIS VGI application that can be used by the general public to
upload geo-locational information for a number of phenomena.
Methods
The first section of this lab addresses the creation of a
map document that will later be used to publish services to an online server. In
order to set domains for the feature classes, the properties must be edited
within the geodatabase for the VGI application. This is when coded value
domains can be set, for example a 0 representing a red fire hydrant and a 1
representing a yellow fire hydrant. The VGI application in this lab will
display 3 feature classes each with domains including fire hydrants (red or
yellow), sidewalks (very good or needs repair) and green spaces (lush or needs
fixing). While creating the feature classes, each one can be configured to use
the corresponding coded value domain and include user comments during data
publication.
In order to make our feature classes cartographically
pleasing, we will customize the symbology of each coded value domain. The image
below shows how each feature class will appear on the completed VGI
application.
After a simple basemap is added, the feature classes are
ready to be tested within the map document. For the purposes of the lab, we
placed one of each domain onto the basemap as shown below.
Everything looks good so far, so the next step is to connect
to ArcGIS server publisher. Once connected, all nonessential layers can be
removed from the map document and the VGI features can be shared as a service. Within
the service editor, it is crucial to include “Feature Access” as a capability.
This is what will allow end users to edit and add data to the application. Once
the feature has been published, it can be referenced within a JavaScript code
and displayed in the application.
For this lab, we will be editing an existing VGI application
instead of creating a new one. The existing application is based in Washington
D.C. and was created for the collection of point, line, and polygon hazard
features. The first step is to locate the coordinates within the JavaScript
code and replace the Washington D.C. coordinates with Eau Claire coordinates.
Next, all of the point, line, and polygon feature URLs will be replaced by the
URLs for the services that we created on the server. After changing the title
to suit this lab, the application is up and running.
The final portion of this lab
had each student construct his or her own VGI application. I chose to build an
application that mapped out the emergency telephones located on the University
of Wisconsin- Eau Claire campus. The end user can specify if each telephone
located in a well lit or dark area during night hours, and include any other
comments if necessary (up to 80 characters). The only challenge encountered
during this portion of the lab was attempting to use an aerial image for a
basemap instead of a topographic map. The topographic map works fine but the
UWEC campus is not detailed within the basemap and it may be difficult for
end-users to find the desired location for their data.
