ArcGIS  Tags: arcgis gis maps mapping data  

ArcGIS® is a desktop mapping program produced by ESRI (Environmental Systems Research Institute, Inc.) that allows you to create your own maps from scratch starting with geographic data in electronic form. There are several interrelated component programs, the basic ones being ArcCatalog, ArcMap, and ArcToolbox.  These three components comprise what is now known as ArcGIS Desktop, or ArcView.  When other advanced components are added, it comprises ArcGIS Workstation, or ArcInfo.

It is a complex program.  This guide will give a skeletal description of the program and will point you in the right directions for more help, but can't begin to explain how to use the program. Users need to be familiar with Microsoft Windows® and must be willing to spend some time to learn how to use ArcGIS.  Facility with a spreadsheet or statistical package is also useful for working with data.

ArcGIS uses the concept of a Geographic Information System (GIS) to build maps in which each category of spatial feature is a separate layer. The layers are spatially "registered" so when the user overlays them the program can line them up correctly  to build a map. There are several types of layers, and the user has many choices regarding how to depict them.  The first three listed are called "vector layers" and contain individual features that the program can distinguish.

• Point (e.g., buildings, landmarks).  Zero-dimensional.

• Line, or arc (e.g., roads and streets, streams, railroads, power lines). One-dimensional.

• Polygon (e.g., political entities, census geographies such as tracts). Two-dimensional.

• Raster images (e.g., an aerial photograph or scanned topographic map).  Contrasting with a vector layer, these are a bitmapped images in which the program cannot distinguish features, but useful as backdrops for overlaying other layers.

Data can be associated with the spatial features, and mapped or analyzed:

• There can be attributes, or spreadsheet data, associated with each feature in a layer (e.g., demographic data for each Census Tract).

• Data tables (e.g., database or spreadsheet files) can be added ("joined") to a layer if there is a common field (e.g., census tract number).  The preferable format to use is dBase.

The program can also map spatially referenced data files in some spreadsheet and database formats (e.g, if one field contains latitude/longitude coordinates).  Tables that contain address data can be "geocoded" to map the locations based on a street layer.  Advanced users can open a non-registered raster image and register it using the program's functions, or vectorize features from a raster image.

You can also add your own information to a map with drawing and writing tools.