Introduction to GIS

What is GIS?

A system for capturing, storing, analyzing, managing, and presenting spatial or geographic data.

List the five components of a GIS.

Hardware, Software, Data, People, Methods.

What are common GIS software packages?

ArcGIS, QGIS, GRASS, Manifold, MapInfo.

What are the two main spatial data models in GIS?

Vector and Raster.

What is vector data best for?

Representing discrete features with points, lines, and polygons.

What is raster data best for?

Representing continuous data like elevation, temperature.

What is topology in GIS?

The spatial relationships between vector features (e.g., adjacency, connectivity).

What is a map projection?

A method for representing the curved surface of the earth on a flat map.

What is the difference between geographic and projected coordinate systems?

Geographic uses latitude/longitude; projected uses X/Y on a flat plane.

What is a datum?

A model that defines the position of the spheroid relative to the center of the Earth.

What are common sources of GIS data?

Maps, GPS, remote sensing, digitizing, government databases.

What are DOQ, DRG, and DEM?

Digital Orthoquad, Digital Raster Graphic, Digital Elevation Model.

What is a feature class?

A collection of similar features (e.g., all roads).

What is a feature dataset?

A collection of feature classes with the same spatial reference.

What is a spatial join?

Combining attributes based on spatial relationships like containment or proximity.

What is a buffer in GIS?

A zone created around a feature at a specified distance.

What are common vector overlay tools?

Intersect, Union, Clip, Erase.

What is map algebra?

Cell-by-cell operations on raster data using math and logical operators.

What are local, focal, zonal, and global operations?

Operations based on a single cell, neighborhood, zones, or entire dataset.

What is a DEM?

Digital Elevation Model, a raster representation of terrain elevations.

What are slope and aspect?

Slope is steepness, aspect is the compass direction a slope faces.

What is a viewshed analysis?

Determines visible areas from a specific observation point.

What is spatial interpolation?

Estimating values at unsampled locations based on nearby known values.

What is IDW?

Inverse Distance Weighted interpolation; closer points influence the estimate more.

What is a Thiessen polygon?

An exact interpolator assigning values based on the nearest sample point.

What are the three segments of GPS?

Space (satellites), Control (ground stations), User (receivers).

What is DGPS?

Differential GPS; improves accuracy using a known base station.

What is WAAS?

Wide Area Augmentation System; improves GPS accuracy via satellite corrections.

What is remote sensing?

Acquiring data about Earth’s surface from aerial or satellite imagery.

What are the types of resolution in remote sensing?

Spatial, spectral, temporal, and radiometric.