An overview of Web GIS

A common task that you will perform as an ArcGIS user is to design and author GIS maps for use by others in (and perhaps outside) your organization. You will publish those maps using a range of GIS servers and applications, and your end users will utilize these maps to address any number of questions, missions, and problems.

This help section provides an overview for this map authoring task and a guide for designing and creating effective maps using ArcGIS. One of the primary focuses of this section is to provide guidance on how to build maps that are deployed on the Web using ArcGIS Server.

Comparing printed maps and computer maps

A printed map is a visual representation of an area organized as geographic features, symbols, and descriptive text onto a page. The primary map element is the map frame, and it provides the principal display of geographic information. Within the map frame, geographic entities are presented as a series of map layers that cover a given map extent—for example, map layers such as roads, rivers, place-names, buildings, political boundaries, surface elevation, and satellite imagery. Most maps are two-dimensional, but 3D representations are also often used.

Electronic or digital maps are maps that are displayed and used on a computer. There are various kinds of digital maps. The simplest are map pictures or photographs that present geographic views of an area of interest. For example, here is an extract from a digital map picture of a USGS Digital Raster Graphic (DRG):

A portion of a USGS digital raster graphic (DRG), which was created by scanning and georeferencing the USGS paper 1:24,000-scale topographic map series for the United States

These simple map types can be georeferenced so that they can be overlaid with other map information. This also enables you to pan, zoom, and navigate around the map to view various areas. The map, however, is still a relatively simple view (albeit often containing exquisite cartography). It's just a picture. Users often overlay (or "mash up") their own digital information on these types of computer maps.

GIS systems can be used to create both of these types of maps. Yet another type of map exists that enables you to use this map view to access further information about the features in the map. These more intelligent maps provide a window into rich geographic information for an area. Because they are interactive, they can also include a series of tools or operators that allows you to access and work with geographic information. We refer to this as a GIS map.

GIS maps

Like these other map types, GIS maps provide a visual representation of geography, but they also provide two additional and very important capabilities:

• GIS maps provide "windows into geographic databases." You can use the GIS map as the user interface to work with geographic information for each of the map's layers. For example, you can point at a feature to list descriptive and attribute information about it. Or you can select a series of features that match a certain criterion (for example, show me all streams containing a particular fish species and whose water flows exceed some threshold value).
• GIS maps can also include a series of spatial operators that enables you to work with the rich geographic information that is held in one or more geodatabases. Key GIS operators enable you to exploit the spatial relationships that are inherent in geographic datasets. For example, you can buffer the roads in a map and overlay these buffer zones with locations of events to study important relationships (for example, show the locations of children with asthma that live within 100 meters of a major road or highway, or perform a spatial statistical summary to demonstrate the relationship of childhood asthma and proximity to major roads).

Each GIS map combines the power of visualization with a strong analytic and modeling framework that is rooted in the science of geography. It's this ability to tap into rich GIS databases and sophisticated spatial operators that enables each GIS map to address a range of problems and needs.

As an ArcGIS user, one common task is authoring and publishing GIS maps for use by people in your organization. These GIS maps help your users perform their daily work, visualize situations and issues, understand and gain insight, and communicate more effectively.

Characteristics of GIS maps

GIS maps provide a powerful metaphor to define and standardize how people use and interact with geographic information. GIS maps provide the primary user interface for most GIS applications. Users can point to map features to display information about them, discover new relationships, perform editing and analysis, and efficiently communicate results using geographic views such as interactive 2D maps, 3D scenes, and 3D globes.

You can think of each GIS map as an interactive computer application that you access and use on a computer or a mobile device. The GIS map provides a user interface to GIS. Each GIS map application contains a map view plus tools and operators to work with the map's contents. Here are some key characteristics of these GIS maps:

• GIS maps can be multiscale. Increasingly, maps on the Web are designed to automatically portray information at a range of map scales as you zoom in, zoom out, and pan around the map display –- for example, in some maps on the Web, you can move from a global view to a national,, statewide, regional, or city view, down to a street-level or city-block view.
  Consumer maps on the Web, such as Google Earth, Microsoft Bing Maps, and Google Maps, make very effective use of multiscale maps. As a result, end users' expectations for the multiscale behavior of their GIS maps are changing as well. Most users will expect similar multiresolution map display behavior as they zoom in and out on their map applications. As a map author using ArcGIS, you can create and share multiresolution maps for your area of interest at the scales that are needed to support the work of your organization.
• GIS maps are interactive. You can display feature information by selecting and querying features within the map. When required, you can add new map layers to present new or derived information in order to address a particular problem or perform a task.
• Each GIS map has a set of tools that is included as part of its user interface for working with the map's contents (that is, for working with the map layers and the datasets they represent). Capabilities can vary from common map query and identification tasks to address geocoding, routing, data compilation and editing, modeling and geographic analysis, and so on. Many maps contain custom tools that help end users accomplish critical tasks that are part of a workflow.
• Each GIS map has an associated GIS map application that supports a set of map operations and uses. Each map application includes an assortment of GIS tools and operators that you can use to work with the map's contents.

  For example, GIS maps can be deployed using high-end professional GIS applications (for use with ArcMap, ArcScene, or ArcGlobe), 3D maps (used with ArcGIS Explorer), Web maps, specialized map applications built using ArcGIS Engine, and GPS-enabled mobile maps (built using ArcGIS Mobile) that can be taken into the field.

• GIS maps often fuse information from a range of Web map services. The ability to mash up information and tools from multiple sources is quite powerful. For example, many users fuse their GIS map layers into a Google Earth or Google Maps display.
• Some GIS maps can have dynamic displays and animate the display of information through time.