FANR 3800 – Lecture Exam 1

GIS

A system for capturing, storing, analyzing, and displaying spatial (location-based) data.

Vector Data Model

Represents features as points, lines, and polygons.

Raster Data Model

Represents space as a grid of cells (pixels) with values.

Point Feature

A single XY coordinate representing a discrete location.

Line Feature

A series of connected points representing linear features like roads and rivers.

Polygon Feature

A closed shape representing area such as forest stands or property boundaries.

Attribute

Non-spatial information stored in a table about a feature.

Attribute Table

A table of rows (records) and columns (fields) storing feature data.

Field

A column in an attribute table.

Record

A row in an attribute table representing one feature.

Shapefile

A vector file format storing geometry and attributes (.shp, .dbf, .shx).

Feature Class

A collection of similar features stored in a geodatabase.

Geodatabase

A structured GIS database that stores spatial data.

Spatial Reference

Defines coordinate system, datum, projection, and map units.

Datum

A mathematical model of Earth used for coordinate calculations.

WGS84

A Geographic Coordinate System using decimal degrees; used by GPS.

Geographic Coordinate System (GCS)

Uses latitude and longitude in decimal degrees.

Projected Coordinate System (PCS)

Uses a flat coordinate system with linear units (meters or feet).

UTM

Universal Transverse Mercator; a projected coordinate system divided into 60 zones.

UTM Zone 16N

Covers western Georgia including Athens and UGA.

UTM Zone 17N

Covers eastern Georgia including Savannah.

Why use UTM instead of WGS84?

UTM allows accurate distance and area calculations in meters.

Distortion

Error introduced when projecting a curved Earth onto a flat map.

Decimal Degrees (DD)

Coordinate format expressed as whole degrees and fractions.

Degrees Minutes Seconds (DMS)

Coordinate format expressed as degrees, minutes, and seconds.

Convert DMS to DD

Degrees + (Minutes ÷ 60) + (Seconds ÷ 3600).

Digitizing

Manually creating vector features from imagery.

Calculate Geometry

Tool used to compute area, length, or coordinates.

Attribute Query

Selecting features based on non-spatial characteristics.

Spatial Query

Selecting features based on spatial relationships.

SQL Query Structure

[Field] [Operator] [Value].

AND

Selects features only if all conditions are true.

OR

Selects features if at least one condition is true.

Buffer

Creates a zone around features at a specified distance.

Clip

Extracts portions of one layer inside another boundary.

Erase

Removes areas that overlap another layer.

Intersect (Overlay)

Creates new features where two layers overlap and combines attributes.

Union

Combines all areas from two polygon layers.

Difference Between Query and Overlay

Query selects whole features; overlay creates new features.

Proximity Analysis

Analysis based on distance between features.

Unique Values Symbology

Symbolizes features based on an attribute field.

Select By Attributes

Tool used to perform attribute queries.

Select By Location

Tool used to perform spatial queries.

Multipath Error

GPS error caused by signal reflection off surfaces.

Management Question Comes Before Tool

GIS workflow should be driven by the problem, not the software.