GIS Web Mapping Services
Introduction
Web mapping is the process of designing, implementing, generating and delivering maps on the web. GIS web mapping service emphasizes on being able to perform analysis and different geoprocesses when compared with a regular web map. GIS web mapping makes it easy share data either within or between an organization or a single user across the web. A web delivery form of GIS can be tailored to meet the end user(s) specific need and can be modified to take into account new changes that needs to be made and the data is centrally managed
A web mapping service can be implemented using a number of technologies, for this course the ArcGIS Server by ESRI was used to implement web mapping applications and projects.
ArcGIS Server and Spatial Database (ArcSDE)
ArcSDEs are used in accessing and managing geospatial data within a relational databases. It is a server-software sub system by ESRI and can be used with other ESRI products such as ArcGIS Server, as well as custom applications to store, use and manage all GIS data in the database management system; in this case PostgreSQL. ArcGIS Server helps put the necessary geographic information from the ArcSDE database on the web.
Creating An ArcSDE Database
Creating an ArcSDE geodatabase was done using Esri's ArcCatalog. The geodatabase was created with the GEWA dataset that was used in the previous section. The feature dataset of the GEWA shapefiles were stored in the geodatabase and SQL statements (view here); was used to create views in PGAdmin for the fish sampling locations, game-fish and non game fish data in PGAdmin. The views and feature classes (ArcSDE database) were displayed differently in the ArcCatalog interface and PGAdmin interface. In both interfaces you could see the objects created with both ArcCatalog (feature dataset) and PGAdmin(views), but PGAdmin had an ArcSDE system tables which stores metadata about the tables in the geodatabase.
structure of database displayed in PGAdmin with items denoting the difference between objects created using ArcGIS and PGAdmin(click to enlarge)
structure of database displayed in ArcCatalog with items denoting the difference between objects created using ArcGIS and PGAdmin(click to enlarge)
A map document (.mxd file) was created that incorporated the fish sampling locations that were created as a tabular view and displayed as spatial data. The final map shows the fish sampling locations as points data. A base imagery was added for better visual appeal.
Map showing the fish sampling locations(click to enlarge)
Creating a Web Service using ArcGIS Server
ArcGIS Server Manager allows you create and edit web mapping applications that shows the geographic information that on wants to run on the ArcGIS Server. The manager lets you tailor your web application to the needs of the user. Creating a web mapping application in ArcGIS server is straight forward. it is advisable to have on hand detail about what you really want to put on your web map and avoid redundant information. Set a clear definition of the purpose of the web application to be created.
Query and Geoprocessing Web Applications/ Maps
The map document created previously would be uploaded in ArcGIS Server and options would be set in the process of creating the application to enable the user run queries, geoprocesses and other tasks such as printing the map. In my application, I built a query so the end user can query the location of a particular game or non game fish type. I also built a query so the user can select a fishing location and view all the associated data with that location.
querying the game fish layer, with the locations of where the game fish were observed highlighted in blue pushpins on the map
One of the sample locations selected, with the associated game fish and non game fish data displayed
Geoprocessing tasks were also implemented in my application. A model was created using ModelBuilder in ArcGIS desktop, this model holds the geoprocessing tools and script that help automate a GIS operation. This geoprocessing model was added to the map document as a tool layer, this is the key to getting the geoprocessing service to work with the map service. For my application, i created a task that allows the user to specify a buffer distance around existing buildings and identify the vegetation that falls within the buffer area, i.e. clip the vegetation data.
Geoprocessing model created in ArcMap(click to enlarge)
final .mxd map(click to enlarge)
web application interface with the layers and legend widget(click to enlarge)
Application interface with the results of the geoprocessing task(click to enlarge)