The Forestry Source - February 2013 - (Page 14)
GIS for Foresters
By Yanli Zhang, Matthew McBroom,
Jason Grogan, Paul R. Blackwell
ccording to Wikipedia, crowdsourcing is a process that involves
outsourcing tasks to a distributed
group of people. The difference between
crowdsourcing and ordinary outsourcing
is that a task or problem is outsourced to
an undefined public rather than a specific
group, such as paid employees. In fact, the
best example of crowdsourcing is
Wikipedia itself, whose articles have been
written collaboratively by volunteers
around the world.
With the development of web-based
GIS technology, it is now possible to collect spatial information through crowdsourcing, even for general GIS users.
Esri’s Education Programs team recently
published an article about a crowdsourcing method, “Fun with GIS 128: Crowdsource Your Fieldwork,” at esriurl.com/fun
withgis128. We offer a demonstration of
this method by using ArcGIS to set up a
web service to collect data on the distribution of giant salvinia from the public.
Giant salvinia (Salvinia molesta) is an
invasive aquatic fern from South America.
The plant has had catastrophic impacts on
aquatic ecosystems on several continents.
It damages aquatic ecosystems by outgrowing and replacing native plants that
provide food and habitat for native animals and waterfowl. Texasinvasives.org
has an online form for the public to report
occurrences of giant salvinia (www.texas
rt_id=1). Latitude and longitude are
needed for location identification. However, users must obtain this information either by other means such as a GPS unit or
by using the pop-up Google Map window.
Although this works well enough, a webbased GIS application for collecting such
information would be much more convenient and user friendly.
The development and deployment of
such web-GIS applications is now quite
Crowdsourcing with ArcGIS Online for Natural
Figure 1. Feature access settings in the Service Editor.
Figure 2. Sharing settings in the Service Editor.
simple. The procedure involves two basic
steps. The first step is using ArcGIS Desktop 10.1 to set up the spatial data and map.
For our demonstration, we created a point
feature class with attributes matching the
information to be collected. In this case,
the feature class was salvinia and the
fields were similar to those on Texasinvasives.org, such as the reporter’s name, email, and report date. A relationship class
allows for attaching photos and other files.
We added a Bing map as a basemap to
provide the user with reference information. The newly created feature class was
empty, so for demonstration purposes we
added a feature at Caddo Lake, Texas,
where giant salvinia has been a big problem in the past few years.
The second step for the demonstration
requires an account with ArcGIS Online,
which employs cloud computing technology
to provide access to ArcGIS Server functionality. Currently, Esri provides a 30-day
free trial; thereafter, the lowest price category is $2,500 per year. We used the free
trial to implement this project. We published
the map as a web service through the “Share
as” function of ArcMap.
Figure 3. The ArcGIS Online application lets anyone post data about giant salvinia. The green triangles are example locations added for
The Forestry Source
Here are the settings needed to configure the service: First, select “hosted services on ArcGIS Online.” There are three
points you need to pay attention to for this
kind of project. First, “Editable feature
services” is the key to setting up this
crowdsourcing application, because map
users—members of the “crowd”—will
need to create, delete, query, and update
the salvinia feature class (Figure 1). Second, make sure the service is shared to the
public on the last page of the Service Editor (Figure 2). This sharing property can
be modified later at ArcGIS Online. In the
Service Editor, click Analyze to make sure
your map can be published as a service.
The most common problem happens when
the basemap cannot be published directly
to a service and needs to be removed.
When the service is published, users can
choose from various basemaps as the
background. The last step is to publish the
service by clicking the “Publish” button.
The new web service may be accessed
at www.arcgis.com. No ArcGIS Online
account is needed. Users need only search
for the map and open it online. Our example is named GiantSalviniaDistribution.
Click on the Open button to access a list of
three ways to open the map. Most users
will choose ArcGIS Online; the other options are ArcGIS Explorer Online or
ArcGIS 10.1 for Desktop.
When you open the map, you first see a
world map with a green triangle on east
Texas. When you zoom in, you can click
on the triangle, an example added for the
demonstration, to view and edit the point’s
attribute information and add an attachment. To add a new point, click on the Edit
button, click on the Salvinia layer in the
table of contents, and click on the correct
location on the map. You enter the corresponding attribute information when
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