Spatial Data Overview

What Is GIS?
Definition: A geographic information system, or GIS, is a computerized data management system used to capture, store, manage, retrieve, analyze, and display spatial information.

Spatial Data: Spatial data are central to any GIS. Spatial data are commonly called themes or layers. Data layers within a GIS are considered spatial data because they have been geographically referenced. That is to say, the data have been linked to a geographic coordinate system. The most common types of spatial data are vector (node or point based) and raster (cell or pixel based) data. Vector data are represented by either points, lines (arcs), or polygons. A good example of vector data would be a "roads" layer. Common forms of raster data are aerial photography and satellite imagery. (See Data Inventory for a complete list of all data layers available in the Northern Puget Sound Ecological Characterization (NPSEC) GIS.)

Metadata: Metadata are essential information about spatial data and they relate to the entire data set rather than objects within the data set. Metadata usually include information such as the date, source, map projection, scale, resolution, accuracy, and reliability of the information, as well as format and structure of the data set. Metadata have been included for all spatial data layers within the NPSEC GIS.

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Overview of Map Gallery
Several GIS maps are included in the NPSEC Map Gallery. Each map contains collections of selected spatial data from the NPSEC GIS and is ready for the user to begin exploring. A sample view of each map, along with its title, has been provided in the Map Gallery. The gallery also includes a link to the spatial data that are within each GIS map. Each map is offered in two formats, which are defined below: ArcView 8.x map documents (MXDs) and ArcReader® 8.x published map files (PMFs).

ArcView® 8.x and Map Documents (MXDs): ArcView 8.x is a powerful commercial desktop GIS and mapping software product created by the Environmental Systems Research Institute® (ESRI®). To begin exploring the spatial data of the ArcView MXDs included in the NPSEC GIS Map Gallery, you must already have ArcView 8.x software loaded onto your computer.

ArcReader® 8.x and Published Map Files (PMFs): ArcReader is available to users who do not have access to ESRI's ArcView 8.x GIS software. ArcReader is a free product from ESRI that allows users to view, explore, and print published map files (PMFs). The published map files included in the NPSEC GIS are equivalent in content to the map documents (MXDs). PMFs are dynamic, as they allow the user to do a number of things, including the following: turn layers on and off, zoom in and out, and identify features. Published Map Files cannot, however, be edited. A PMF has been created for every MXD included in the NPSEC GIS Map Gallery.

To use these ArcReader PMFs, you need to have ArcReader software loaded onto your computer. To run ArcReader version 8.3 successfully, you must have Microsoft® Windows® NT 4.0 with Service Pack 6a,Windows 2000, or Windows XP (Home Edition or Professional). For those who do not have ArcReader already loaded onto their computer, download the executable file (217 kilobytes) needed to install ArcReader version 8.3. After downloading it, run the executable (.exe) file and follow the ArcReader installation instructions displayed on your monitor. You can also install the latest version of ArcReader by downloading it from the ESRI Web site.

ArcExplorer®: ArcExplorer is a lightweight GIS data viewer and explorer developed by ESRI. If you do not have access to ESRI's ArcView 8.x software, ArcExplorer lets you add, display and query the data included in the NPSEC GIS. It also gives you the ability to create individual customized maps.

In order to use ArcExplorer, the software (Version 2 or higher) must be loaded onto your computer. To run ArcExplorer successfully, you must have one of the following operating systems: Microsoft Windows 98, 2000, NT, or XP. If you already have an earlier version of ArcExplorer software loaded onto your computer, you must uninstall it before you can install ArcExplorer 2. Download the executable file (12.8 MB) needed to install ArcExplorer. After downloading it, run the executable (.exe) file and follow the installation instructions displayed on your monitor. You can also install ArcExplorer 2 by downloading it from the ESRI Web site.

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Overview of Data Inventory
An inventory of the NPSEC GIS data layers allows the user to access individual data layers along with their associated metadata. The user also has the ability to preview the metadata before accessing individual data layers. In general, the data focus is on species distribution in the NPSEC project area.

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Overview of ArcView 8.x Tutorials
Three tutorials for working with spatial data in a GIS have been included in the NPSEC GIS. These tutorials were designed for use in ArcView 8.x software, since ArcReader and ArcExplorer do not offer the advanced querying and analyzing capabilities found in ArcView. The ArcView 8.x tutorials demonstrate how to query data layers, retrieve spatial data from the Internet, and project data.

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