Introduction to GIS
A Geographic Information System is a computer data management and mapping system that allows you to analyze, manipulate, map, and visualize complex data from data base files. The GIS adds a new dimension to analyzing and displaying information in the forms of maps, charts, and diagrams in a variety of coordinate systems, map projections and scales.

If you rely on old-fashioned survey maps for land information management, you might want to consider upgrading them to digital format. Digital geographic information technology has progressed to the point where it is an extremely efficient and easy-to-use system.

Serious use of geographic information systems (GIS) began in the 1980s as governments, institutions, utilities, and businesses needed to link data to maps. GIS capabilities have evolved into full geographic data management systems organized into collections of computer hardware, software, geographic data. These systems are managed by trained personnel to efficiently capture, store, update, manipulate, analyze, and display all forms of geographically referenced information. GIS can help you answer all of your geographic questions:

• Location—"What is at...?"
  Locations can be described in many ways, including a place name, a street address, a zip code, or a geographical reference such as latitude and longitude.
  
• Condition— "Where is it?"
  This question is the converse of the first and requires spatial analysis to answer. Instead of identifying what exists at a given location, you want to find a location where certain conditions are satisfied (e.g., an unforested section of land at least 150 square acres in size, within 100 meters of a county service road, and with soils suitable for agriculture).
  
• Trends— "What has changed since...?"
  This question might involve both of the first two and seeks to find the differences within an area over time.
  
• Patterns— "What spatial patterns exist?"
  You might ask this question to determine the cause of periodic power outages in a certain area. By locating outages over time, trends can be easily identified.
  
• Modeling— "What if...?"
  Questions of this nature are posed to determine what happens, for example, if a toxic substance seeps into the local ground water supply. Answering this question requires geographic and other planning information.

In summary, GIS is used to capture, store, analyze, manipulate, and display information to help your planning and decision-making.

Example: GIS in Government
GIS technology is used around the world. Early uses in Europe involved land registration management for ownership and taxation purposes, but Great Britain concentrated primarily on developing utility systems and creating a comprehensive topographic database for the country.

Canada developed applications for managing their forests. The application helped them plan the volume and access location of timber to cut, and to report the results to the Provincial governments. China and Japan both developed similar applications that also monitored the environmental effects and helped create models for possible future changes.

Today, the number and variety of GIS applications is impressive. The amount of geographic data that have been gathered is enormous and includes volumes of satellite data collected from space. Local governments such as counties and cities use GIS for planning and zoning, property assessment and land records, parcel mapping, public safety, and environmental planning. For example, a county or community can use a GIS to:

• Develop a current street and address inventory.
• Locate and map existing water and sewer lines. Identify and map all lines that need maintenance in a given year.
• Locate zoning designations of all land parcels.
• Identify current land uses for compliance with zoning and subdivision ordinances.
• Identify and map existing population by census or planning areas
• Identify all capital improvements made within a designated council district or any other community sector.
• Identify where crimes or auto accidents are occurring.

Resource managers rely on GIS for fish and wildlife planning; management of forested, agriculture, and coastal lands; and energy and mineral resource management.

GIS supports the daily activities of automated mapping and facilities management with applications for electricity, water, sewer, gas, telecommunications, and cable television utilities, using capabilities such as load management, trouble call analysis, voltage drop, base map generation and maintenance, line system analysis, siting, network pressure and flow analysis, leak detection, and inventory. Demographers use GIS for target market analysis, facility siting, forecasting, and planning. GIS also has an increasing role in supporting education and research in the classroom, the computer lab, the research institute, and the public library.

GIS is the most efficient and easiest method to update, edit, and analyze any data that can be linked to a map of the land in your city or county. Every level of city and county government will benefit from the tools that a GIS can provide to facilitate sound administrative decisions. GIS is truly a general and multipurpose analysis tool.

Example GIS Workspace

	Layer 5 - an address location map (geographic locations of addresses with other database information)
	Layer 4 - a street map (a local street/road grid helps locate objects and boundaries)
	Layer 3 - a land use map (color coordinated to individual land use regions)
	Layer 2 - a map of surface water (rivers, arroyos, lakes, etc.)
	Base Layer - a digitized raster image of the area of interest

How GIS Works
GIS technology can be defined as "data visualization" because the GIS takes current data, matches them to geographic coordinates and allows the user to display the data graphically. Once the data are mapped, any information in the file can be manipulated and displayed in a visual, geographic format. Variables can be changed, "what-if" scenarios run, and the final results can be displayed and printed in full color. With GIS, the maps are always as up-to-date as the files used to create them.

A GIS map is made up of various layers. Each layer can contain descriptive or thematic geographic data. Map layers can be combined, processed, and analyzed in any number of ways. As any layer is updated, all interrelated layers are also updated. This allows you to visualize, link and create new maps to fit your needs. You can map and analyze any information that can be tied to a specific area or address.

See Flowchart 1. for an illustration of the GIS process.

Can your current data be used in GIS?
The basic components of a GIS consist of a computer system that has ample storage space for city or county database and graphical data, and can display graphics well (these days, just a couple of steps above department store computers!), and GIS software such as MapInfo, ArcView GIS, or Arc/Info GIS. Most GIS software is not difficult to learn, and with a few short lessons, a new user can begin performing high-powered tasks that previously took many hours, days or even weeks to accomplish.

The most complicated task is creating base information and maps. Once developed, base maps are invaluable management and decision-making tools. The maps are used in all levels of GIS work, and make GIS analysis work a snap. Unfortunately, the process of developing the maps is not an easy one, but once developed, these maps are quite easy to maintain and update.Putting data into digital format can be accomplished in several different ways. Unfortunately, none of the methods are very easy.

• Digitizing Data
  Previously, the most common method for converting hard-copy geographic data into digital format was manual hand tracing of existing survey maps (also known as hand digitizing, or simply digitizing). The method is not complicated, but requires many hours of tedious tracing. If done carefully, digitizing can produce fine digital data, but it can be costly, and the user must be proficient with a digitizer and the GIS software. Base maps are very important documents, and detail is crucial.
• Aerial Photography
  Aerial photography with raster-to-vector conversion is the most common choice among urban areas because of its speed. Geo-referenced photos (raster images) are converted to GIS base maps (vector data) with powerful software tools. The vector data (lines, points, and polygon regions) are then cleaned and databases are attached for input of your data. Other layers of data are now able to be created as overlays on top of your county or city land base maps.
• Survey Map Tracing with GPS Locating
  One of the most cost-efficient and accurate methods of developing digital base maps is to use survey maps together with a global positioning system (GPS). Survey maps can be scanned into a raster image and converted to vector data using the raster-to-vector method previously described. The GPS is used to locate features that are newer than the survey maps, such as locations of new property lines, utility locations, or street lines. GPS technology can be easily used by county or city personnel on a regular basis to update new geographic features.

See Flowchart 2. for an illustration of the raster to vector conversion process.

ARC GIS Services
ARC is a New Mexico leader in the field of GIS. Since 1990, ARC has used GIS technology in many of its projects. ARC began GIS work with two of today's leading GIS software manufacturers, Arc/Info and MapInfo. Today, ARC combines the power of these programs with ArcView GIS, as well as other GIS tools and specialized maps. ARC can apply GIS technology to:

• management of:
• facilities
• natural resources
• economic resources
• hazardous waste
• transportation systems
• mapping the distribution and status of:
• population
• socioeconomic variables
• agriculture
• urban development
• land use/zoning
• transportation
• environmental impacts
• infrastructure
• finding optimum locations for:
• business
• industry
• public facilities

ARC can develop your county base maps and put you on the right track for developing your own GIS layers to manage any type of data - utilities, roads, property/taxes, emergency response, demographics, land use, zoning, hydrology, and resource management, just to name a few. Developing base maps is just the first step. The true power of GIS lies in its ability to inventory, relate, and analyze data. Putting data to your maps is what we want to help you do. Each city and county has data that is specific to that area, and we would like to help you develop your GIS maps to fit your own individual needs. GIS will help you make sound administrative decisions that will save you time and money.

For more information and a hands-on demonstration of GIS technologies, please contact us.

Flowchart 1. The GIS Process

1. Create databases about existing or projected conditions:
   
   
2. Enter data in various layers:
   
   
   
3. Analyze and link layers to create unique maps:
   

Flowchart 2. Raster to Vector Map Conversion