Some Things to Study for Quiz #1

You should review your notes from lecture, the website content, any readings that were assigned, your THX exercises, any handouts given in class, etc.  Below are a few key points you should be familiar with, in addition to the information contained in the sources just mentioned.

Provide a definition for Geographic Information Systems that uses some of the commonalities of most GIS definitions.

GIS can use any data that is spatial.  Some examples of spatial data would be:
    1.  A list of classroom locations on campus.
    2.  A table of freeway interchange sites in San Diego County.
    3.  A map of land use in Utah.
    4.  An inventory of the burned areas from the Cedar Fire.
Examples of data that is not spatial include:
    1.  A list of freeway names for California.
    2.  A list containing food items sold at the Grossmont College Cafeteria.
    3.  A directory of Grossmont College instructors names and phone numbers.
    4.  A table containing all plants within the Asteraceae plant family.

All Maps are inaccurate because of the inherent distortions that occur when the 3 dimensional earth is projected onto 2-dimensional map space.

To combine data into a GIS, the datum, coordinate system, and projection must be the same for both data sets.

Metadata is information about the data.  Some examples of metadata include:
    1.  When the data was produced.
    2.  What purpose was the data produced for.
    3.  Who produced the data.
    4.  What datum, coordinate system, and projection was used.

Know a little about the history of GIS including, but not limited to, things like, what does ESRI stand for and who founded it?; or what are the five phases of GIS development?;  Which phase is the most recent?

A datum is a model that defines the size, shape, and orientation of the Earth.  A datum provides an origin that allows coordinates to be meaningful.  Datums are developed using information from an ellipsoid model (such as the Clarke 1866 ellipsoid), and error is introduced into the datum whenever it is applied to reality.  NAD83 is a vastly improved datum over NAD27, due to advances in Remote Sensing (satellite and airplane imaging of the Earth) and GPS (Global Positioning Systems) technologies.

Know what the difference is between Vector Data and Raster Data.  In addition, remember the following:
    1.  Features on a map, such as a lake, that are vector data could be represented with a point at smaller scales and an area at larger scales.
    2.  Raster data that has a higher pixel (cell) count will show more detail than raster data with a lower pixel count.  Just like when you take a photo with a digital camera,  the higher the megapixels, the more detailed the photo and the more you can zoom into, or enlarge, the photo later.

Know about raster data classification and know how the different decision rules are applied (as done in class) such as "Winner Takes All", "Edges Separate", etc.

Which of the following scales is larger?
    a.  1:3,250
    b.  1:5,230
Of the scales above, which will show more area?  Which will show more detail?

Know what projections are.  Know the most common types as discussed in class and what associated distortions (distortions of shape, area, distance, or direction)
or advantages each has.  For example:
    1.  Conformal projections preserve shape, but distort area.

The most common file types in ArcGIS are:
    .mxd = map file
    .lyr = layer file
    .shp = shape file
    .mdb = database file

The simplest form of vector data is a shapefile.  As the shapefile is brought into ArcGIS, most modifications, display characteristics, and other changes to the data are saved in an associated layer file.  Thus, a layer file cannot exist without the shapefile.  The shapefile contains the essential spatial information that describes the feature types and their locations.