Geographic Information Systems (GIS) combines layers of information about a specific geographic location to provide a better understanding of that location in a spatial context. More specifically, GIS is a way to manage, store, analyze, and represent spatial data. Figure 1 shows this combination of data layers.

GIS not only allows you to create a map of an area, such as a city block or a submarine canyon, it also allows you to ask a question about that area. Based upon the availability of GIS data, you decide what pieces of information are layered together to produce an answer to your question. As an example, a marine biologist wants to find areas of the Monterey Bay National Marine Sanctuary where rockfish live at depths greater than 500 meters. This biologist uses specific GIS data layers, such as rockfish distribution and bathymetry (bottom contour) to produce a map of the Sanctuary showing the required information. The biologist can then analyze the map to locate these areas of interest. Further data, such as socio-economic information regarding fishing, may also be added.

Performaing GIS analyses can sometimes require the use of multiple types of spatial data to produce the desired outcome. These data types are explained below:

Vector data - points, polylines, polygons (study locations, the California coastline and marine protected areas are examples of these three, respectively). View an example

Image data - aerial and satellite photography, for example. View an example

Raster data - continuous numeric values, such as bathymetry and salinity. View an example

Tabular data - most spatial data has tabular data associated with it. For example, study locations could have many fields associated with each record in space, such as the investigator's name and address, the duration of the study, the study type, etc. Additional tabular data can be related to form large networks of data that allow for powerful analysis. View an example

GIS is also widely used in land-based systems, from city planning, to highway management, to environmental impact. Typically terrestrial data is easier to acquire than marine data. However, advances in technology and the increase in marine-related studies have vastly increased the amount of marine GIS data available. This has enabled resource managers, scientists, and the public to not only visualize and examine marine data relationships in a new way, but to also answer (and ask) many questions.

To examine SIMoN's GIS data, click the 'launch map viewer' button on the previous page. SIMoN Interactive Maps will open in a new window and allow you to ask a question and create a map to provide the answer.

Questions regarding GIS? Please email Chad King at chad.king@noaa.gov. For more information on GIS, visit http://www.gis.com