Geographic Information Systems (GIS) Fundamentals

GIS (Geographic Information Systems) uses two fundamental data types: Raster data (grid-based, like satellite imagery) and Vector data (coordinate-based, representing points, lines, and polygons). Remote Sensing is a data collection method that produces raster data, not a data type itself. Buffering is an analysis operation, not a data type.

Lines of latitude (parallels) run east-west around the Earth and are always parallel to the equator. Unlike longitude lines, latitude lines never converge and their circumference decreases as you move toward the poles (so B is wrong). Latitude values range from 0° at the equator to 90°N/S at the poles, not 180° (so D is wrong), and only longitude lines pass through the poles (so A is wrong).

GIS maps serve multiple purposes: they visualize data spatially (A), locate specific features (B), and enable comparison of different spatial datasets (C). Since all three individual functions are core uses of GIS, 'all of the above' (D) is the comprehensive correct answer.

Scale = real distance : map distance. Convert both to the same unit: 400 feet = 400 × 12 = 4800 inches. Scale = 4800 inches : 3 inches = 4800:3 = 1600:1, which is written as 1:1600. This means 1 inch on the map represents 1600 inches in reality.

In map scales, a smaller denominator means a larger scale (more detail, less area covered). 1:1000 has the smallest denominator, so it shows the most detail and covers the smallest area - making it the largest scale. Conversely, 1:100000 covers a huge area with less detail, making it a smaller scale.

The three main families of map projections are planar (azimuthal), cylindrical, and conic - all based on projecting onto different geometric surfaces. 'Geographic' is not a projection type; it refers to the coordinate system (lat/long) used, not the projection method itself.

GIS is defined by its five core functions: capture (data collection), storage (database), retrieval (querying), analysis (spatial operations), and display (mapping). GPS is for positioning, surveying is for measurement, and remote sensing is for data collection - none include all five functions.

ArcGIS, GRASS, and Smallworld are all GIS software designed for spatial analysis and mapping. AutoCAD is a CAD (Computer-Aided Design) program for engineering and architecture - while it can draw maps, it lacks specialized GIS capabilities like spatial analysis and coordinate systems.

A geodetic datum is a reference system that defines the Earth's shape (ellipsoid) and anchors coordinate positions to the surface. It's not a single data point (A), a collection (B), or census data (C) - those are just data, not the reference framework itself.

A sketch becomes a map when it has three formal elements: scale (so distances are measurable), direction (north arrow for orientation), and symbology (legend explaining what symbols mean). All three are required - a drawing missing any of these remains a sketch, not a proper map.

The GPS constellation requires at least 24 satellites for full global coverage (4 visible from any point), but currently 30 operational satellites are maintained in orbit. This includes spares and backups to ensure reliability as older satellites fail and new ones are launched.

GIS's core function is integrating spatial data (maps, locations) with non-spatial data (attributes, statistics) to support decision-making. Surveying (A) is about measurement, photogrammetry (B) uses aerial photos to determine geometry, and GIS is not about doing 'all the above' - it has a specific purpose.