GIS Conceptual Foundations 3 — Questions and Answers
Question 1: Which type of coordinate system uses latitude and longitude to describe positions on Earth?
- Projected coordinate system
- Geographic coordinate system (Correct answer)
- Cartesian coordinate system
- Local coordinate system
Correct answer: Geographic coordinate system
A geographic coordinate system (GCS) uses angular units (degrees of latitude and longitude) referenced to a datum to locate positions on Earth's surface.
Question 2: What is the role of a datum in a coordinate reference system?
- It defines the units used for attribute values
- It specifies how the coordinate system is aligned to Earth's surface (Correct answer)
- It controls the color rendering of map layers
- It sets the spatial extent of the dataset
Correct answer: It specifies how the coordinate system is aligned to Earth's surface
A datum defines the reference ellipsoid and its orientation relative to the Earth, anchoring the coordinate system to the physical world.
Question 3: Which GIS data quality dimension measures how well spatial data represents its real-world location?
- Completeness
- Thematic accuracy
- Positional accuracy (Correct answer)
- Temporal accuracy
Correct answer: Positional accuracy
Positional accuracy describes how closely the recorded coordinates of a feature match its true location on Earth.
Question 4: A raster dataset has a cell size of 30 meters. What does this mean?
- Each cell covers 30 square meters of area
- Each cell represents a 30×30 meter area on the ground (Correct answer)
- The dataset was captured 30 meters above ground
- There are 30 rows and 30 columns in the grid
Correct answer: Each cell represents a 30×30 meter area on the ground
A 30-meter cell size means each pixel represents a 30 by 30 meter square area on Earth's surface.
Question 5: What is the main advantage of vector data over raster data for representing discrete features like roads?
- Vector data is always smaller in file size
- Vector data precisely represents boundaries and lines without pixelation (Correct answer)
- Vector data supports continuous surface analysis better
- Vector data is easier to display on screen
Correct answer: Vector data precisely represents boundaries and lines without pixelation
Vector data stores features as exact coordinates, making lines and polygons sharp and scalable regardless of zoom level.
Question 6: What does 'georeferencing' mean in GIS?
- Converting attribute data to spatial data
- Aligning a dataset to a known coordinate system using control points (Correct answer)
- Creating a 3D terrain model from elevation data
- Merging two datasets with the same projection
Correct answer: Aligning a dataset to a known coordinate system using control points
Georeferencing assigns real-world coordinates to a dataset (such as a scanned map or image) by using ground control points to establish spatial alignment.
Question 7: Which layer model concept organizes geographic reality into separate thematic layers stacked on top of each other?
- Object-based model
- Layer cake model (Correct answer)
- Network topology model
- Triangulated Irregular Network
Correct answer: Layer cake model
The layer cake model organizes geographic information into discrete thematic layers (roads, land use, elevation, etc.) that can be overlaid and analyzed together.
GIS Conceptual Foundations 3
Which type of coordinate system uses latitude and longitude to describe positions on Earth?