Mapping and GIS Concepts Flashcards

A GIS database for a municipality contains a parcel layer (polygons) and a water main layer (lines). Which of the following topology rules would be most appropriate to ensure data integrity?

Answer: Parcel polygons must not overlap.

The most critical topological rule for a parcel layer is that individual parcels cannot overlap, as this would represent a physical and legal impossibility. Each distinct property must occupy its own unique space.

A surveyor is preparing a map for a long, narrow state that extends primarily from east to west. To minimize distortion for a State Plane Coordinate System, which map projection would be the most suitable choice?

Answer: Lambert Conformal Conic

The Lambert Conformal Conic projection is ideal for areas that are elongated in an east-west direction. It uses a cone as the developable surface, which intersects the Earth along two standard parallels, minimizing distortion along this axis. States that are long east-to-west typically use this projection for their State Plane Coordinate Systems.

Which of the following best describes the primary function of a geodetic datum?

Answer: To serve as a reference frame for defining the size and shape of the Earth and the origin of a coordinate system.

A geodetic datum is a fundamental component of any coordinate system. It defines a reference ellipsoid, which models the shape of the Earth, and an origin point, which anchors the coordinate system to the physical Earth. This framework is essential for ensuring that all spatial measurements are consistent and relatable.

A topographic map has a contour interval of 10 feet. If two adjacent contour lines are very close together on the map, what does this indicate about the terrain?

Answer: A steep slope

Contour lines connect points of equal elevation. The contour interval is the vertical distance between these lines. When contour lines are spaced closely together, it signifies a rapid change in elevation over a short horizontal distance, which represents a steep slope.

In a GIS, which data model is best suited for representing continuous phenomena like elevation, temperature, or satellite imagery?

Answer: Raster

The raster data model uses a grid of cells (or pixels), where each cell contains a value representing the phenomenon being measured. This structure is ideal for representing continuous surfaces where values change across a landscape, such as elevation from a Digital Elevation Model (DEM) or temperature gradients.

A GIS analyst is tasked with identifying all residential properties within 500 feet of a proposed new highway to send out notification letters. Which spatial analysis technique would be the most direct method to accomplish this?

Answer: Buffering

Buffering is a proximity analysis technique that creates a polygon (a buffer zone) at a specified distance around a point, line, or polygon feature. In this scenario, creating a 500-foot buffer around the proposed highway line feature would allow the analyst to select all property parcels that fall within or intersect that buffer zone.