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Geographic Information System (GIS)

The City has created a very easy to follow and understand Map Guide for the users of their online GIS. It is important to master this guide before continuing. Map Guide

The city of Santa Monica Online Geographic Information System provides geospatial information to its residents, tourists and other interested individuals and groups. We use this award -winning online GIS to demonstrate the fundamentals of GIS. The pictures in this page show some of the features in the city.What is GIS ?

Natural and Constructed Features and Boundaries

To create an information system that stores data about the features that cover the city, the city has identified a variety of constructed and natural features and boundaries to be used by the public. Two of the interactive maps by the City are used in this tutorial. In both of these interactive maps, lines are used to represent linear features such as streets and faults, polygons are used to represent areas such as parks, and points are used to represent trees and street signs. Polygons are also used to show boundaries.
Explore the City of Santa MonicaOnline Property Information System (OPIS)

Layers

After the natural and constructed features and boundaries are identified and prioritized, they must be organized as map layers in a GIS software. In the Online Property Information System interactive map, the layers are under four folders: Administrative Boundaries, Base Map Information, Environment, and Base Map Images. In the Explore Santa Monica interactive map, the layers are also under four folders: Entertainment, Services, Sustainable City, and Transportation. To learn more about using layers and legends , click Help on the Tool bar.
MapTool Help

Patterns, Trends and Relationships

After natural and constructed features and boundaries are represented as transparent layers one above the other in a GIS software, we can unravel the patterns, trends and relationships that exist among layers. For example, if developers are interested to know if a development site is associated with any environmental hazards, they can use the address of the location and display the environmental maps of the city in the Online Property Information System to find fault lines, landslide and liquefaction risks and other hazards . This is where the real power of GIS lies.

Raster and Vector Data Formats

After natural and constructed features and boundaries are identified, raster and vector data types are used to represent them digitally. All the images in this page are raster data format. They are all .jpeg files. Only on the picture to the right have I drawn a line to represent the street, 3 small circles to represent the parking meters and a polygon to represent the grass area. These drawings are in vector format. In the Online Property Information System (OPIS), orthophoto and topo layers are raster, and the rest is vector data format.

Geospatial Databases

A GIS software is basically the union of two powerful softwares, a mapping and a database management software. Every natural and constructed feature- such as a parcel, a tree, a park, a mountain -has its row in a table. Geospatial tables all have a column describing where they are located. This could be an address, zip code, or their longitude or latitudes. Of course GIS software can translate addresses to longitude and latitude so it could be displayed on a map. If we go to OPIS and select a parcel, the row in the table containing the information will be shown to the right of the map. By clicking any attribute such as APS, a page called Assessor Parcel Information Help will appear to explain each column heading.
Assessor Parcel Information Help

Assessor Parcel
Number (APN)
Site Address
Site Zip Code
Condo
Zoning
Land Value
Fixture
Sale Amount
Legal Desc
Assessor Map
                   
                   
                   
Parcel number 3                  
                   
                   
                   
                   
                   

The above table shows ten out of 25 attributes for each parcel in the database. Each parcel occupies one row shown in green. What makes a database a geospatial database is a database that has a column or more describing the location of the feature (red). The address could be represented by two columns representing X and Y showing longitudes and latitudes. So the table has spatial attributes in the table represented by longitude and latitude. It also has non-spatial attributes such as Sale Amount, Land Value, Fixture, and Legal Description. By storing data in a database, we can query (search) the database and map the results of our search. The mapping and database management capabilities of GIS software give users a powerful analytical tool.