Attribute Table: a tabular file containing rows and columns. Attribute tables are normally associated with a class of geographic features. Each row represents a geographic feature. Each column represents one attribute of a feature, with the same column representing the same attribute in each row.

DEM: stands for digital elevation model. DEMs are digital topographic maps that carry data concerning the elevations of a geographic area.

Hillshade: an ARC/INFO and ArcView command that allows a researcher to accentuate an area's topographic relief by positioning a light source at any compass direction and altitude in relation to a DEM. For example, one could position the light source to mimic the rising or setting sun for any position on the globe.

Degree of Slope: a measure of change in surface value over distance, expressed in degrees or as a percentage. For example, a rise of 2 meters over a distance of 100 meters describes a 2% slope with an angle of 1.15.

Aspect: the direction in which a slope or surface faces, especially in the context of exposure. Aspect can be calculated by many GIS, and is usually expressed in degrees relative to North. For example, North is 0 degrees, and South is 180.

Intersect: an ARC/INFO overlay command. Intersect is the integration of two spatial data sets that preserves the data that fall within the area common to both in a new theme.

Union: the outcome of the union command is an output data layer/theme that retains all the elements of all the input data layers/themes.

An unlimited amount of descriptive information concerning each polygon, line, or point can be stored in a relational database called an . For instance, the attribute table for the polygons in Z2HABITATION contains information about each Zone 2 habitation site, such as site number, the date that each was last surveyed/excavated, artifact types previously found on the sites, the names of previous investigators, land ownership, etc. Although you will not need to access attribute tables in this exercise, the ability to link tabular data to geographic locations is one of the most important features of any GIS analysis.

This exercise includes tutorial segments illustrating a variety of GIS maps and commands. There are also segments that provide discussion questions concerning the cultural and ecological factors that influenced rockpile field placement in the Marana Community during the Early Classic Period. To complete the illustrative tutorials and answer the subsequent discussion questions you will need to follow accompanying directions and consider appropriate themes and views when prompted. You will have the following themes and views at your disposal to complete the exercise, although you may not need to use all of them.

Table 1. Theme names and descriptions.
--standard of the study area (Northern Tucson Basin)
-- DEM of the study area
-- map of the study area
-- map of the study area
--the of Z2HABITATION and ECOL2B
--Early Classic Period habitation sites in Zone 2
--Early Classic Period rockpile field sites in Zone 2
--Early Classic Period habitation sites in Zone 4
--Early Classic Period rockpile field sites in Zone 4
--Zone 2's ecologically viable area for rockpile fields based on the elevation and slope characteristics of known rockpile fields
--Zone 4's ecologically viable area for rockpile fields based on the elevation and slope characteristics of known rockpile fields
--the of ECOL2B and ECOL4B
--landform polygons for a portion of the study area
--2 kilometer zones around all habitation sites
--linear archaeological surveys conducted in and around Tucson, AZ
--distribution of isolated Archaic Period projectile points around Tucson

Table 2. View names and descriptions.
--Z2HABITATION and BUFFER2KM
--Z2HABITATION and ECOL2B
--ECOLOGICALLY_VIABLE, Z2ROCKPILES, and Z4ROCKPILES
--ECOLOGICALLY_VIABLE, Z2ROCKPILES, Z4ROCKPILES, Z2HABITATION, and Z4HABITATION
--Z2ROCKPILES, Z4ROCKPILES, Z2HABITATION, Z4HABITATION, BUFFER1KM, and BUFFER2KM
--MARANA_LANDFORM and Z2ROCKPILES

Habitation sites are represented by red polygons and rockpile field sites are represented by blue polygons throughout this exercise. Red polygons that contain small blue circular polygons represent habitation sites that also contain rockpile features somewhere within their boundaries.

As you access the various themes and views be aware that some are at different scales than others. Some data layers, like , contain data for the entire study area, while others, like , contain data for Zone 2 rockpile field sites only-a small portion of the entire study area. To get a sense of this scalar change, compare the size and shape of the polygons provided by with those of the same rockpile field sites in ; the shapes are the same but the size of the polygons in the latter are much smaller because you are looking at a larger area of land at a larger scale. GIS analysts must be vigilant in their use of multi-scalar data so as not to mesh themes that display data at different geographic scales.

 

Buffer: in spatial information systems a buffer zone, or simply buffer, is a polygon enclosing an area within a specified distance from a point, line, or polygon. Accordingly, there are point buffers, line buffers, and polygon buffers. Buffers are useful for proximity analysis, for example, finding all stream segments within 300 feet of a proposed logging area.