Geographic Information Systems (GIS) Exam Notes

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Questions and Answers

What is a geographic datum?

A type of software used for geographic problem-solving

A method for mapping trees in a forest

A system for measuring temperature over time

A position with an attribute value that denotes geographic content (correct)

Which of the following is NOT a characteristic of raster data in GIS?

Ability to represent continuous surface data

Simple data structure

Exact geometry for geographic objects (correct)

Storage of fuzzy objects like wetland lakes

Which of the following geographic problems does NOT utilize geographic position for its solution?

Writing a book (correct)

Forest management

Finding your way in an unfamiliar city

Precision farming

What is one of the disadvantages of vector data in GIS?

Algorithmic complexity Signup and view all the answers

What method can be used to catch temporal change in a spatiotemporal scenario?

Calculation of consecutive differences from time-series data Signup and view all the answers

Which advantage of raster data is primarily affected by its storage requirement?

Loss of topology Signup and view all the answers

When defining geographic problems, which of the following would be considered a valid example?

Assessing climate change effects on forest ecosystems Signup and view all the answers

Which characteristic defines vector data's ability to handle multiple attributes?

Exact geometry Signup and view all the answers

What is a local ellipsoid primarily used for in geodesy?

To approximate the irregular shape of the geoid. Signup and view all the answers

What is one advantage of a secant map projection over a tangential projection?

It results in lesser average scaling errors. Signup and view all the answers

Which GPS technology operates with real-time capabilities?

Network RTK Signup and view all the answers

What defines the primary characteristic of non-real-time GPS systems?

They require stationary observation for accuracy. Signup and view all the answers

How does ortho-correction improve the quality of sensed images?

By adjusting perspective effects caused by sensor position. Signup and view all the answers

Which of the following GPS technologies provides absolute positioning in real-time?

Single Station RTK Signup and view all the answers

What distinguishes a formal map from a map-like depiction?

Formal maps comply with cartographic conventions. Signup and view all the answers

What does the term 'mean radius' refer to when discussing the geoid?

It indicates the average distance from the geoid to the center of the Earth. Signup and view all the answers

What role does a local gravity reference play in the utilization of the geoid?

It provides a consistent reference point for geodetic datums. Signup and view all the answers

How do reference maps differ from thematic maps?

Thematic maps focus on specific attributes, reference maps do not. Signup and view all the answers

Which of the following best describes how inverse-distance-weighted interpolation works?

It combines observations weighted by their distances from the kernel. Signup and view all the answers

What does the term 'isotropic interpolation kernel' refer to?

An interpolation technique assuming uniform distance impacts across all directions. Signup and view all the answers

Which example best illustrates a reference map?

A Swedish GSD terrain-map at scale 1:50,000. Signup and view all the answers

What is a primary characteristic of cartograms used in subways?

They depict systems without formal claims to geographic accuracy. Signup and view all the answers

Which statement is true regarding the relationship between maps and charts?

Maps refer to terrestrial depictions, while charts relate to maritime areas. Signup and view all the answers

What impact does increasing distance between sensor and Earth have on perspective in images?

It decreases the problem of shifting perspective across the image. Signup and view all the answers

Study Notes

Geographic Information Systems (GIS) Exam Notes

Geographic Datum: A geographic datum combines a position (geodetic datum) and an attribute value (geographic content). Geographic problems use geographic positions to solve other problems. Examples include forest management, precision farming, finding your way.
Representation Methods (GIS):
Raster: Advantages include simple data structure, representing continuous surfaces (e.g., temperature, wetlands). Disadvantages include lack of topology, large storage requirements.
Vector: Advantages include precise geometry, multiple attributes per object, well-defined topology, and handling of discrete objects. Disadvantages include high precision requirements, computational complexity, inability to represent continuous phenomena.
Spatiotemporal Change (GIS): A "spatiotemporal scenario" means observing spatial change over time. To track this change in GIS, calculate differences between successive time snapshots. This identifies areas with change and the degree of change.
Geoid and Local Ellipsoid: The geoid is Earth's gravity field and irregularly shaped. A local ellipsoid (mathematical surface) approximating the local geoid curvature is used when projecting Earth's surface onto it. This maintains the gravity reference and relation to the global ellipsoid.
Map Projections (Secant vs. Tangential): Secant projections minimize average scaling error compared to tangential projections. Example: Universal Transverse Mercator (UTM) uses a transversal secant cylinder to cover Earth's circumference.
GPS Technologies: Several GPS technologies exist such as absolute code (absolute GPS), differential GPS, relative phase-shift with post-calculation (statistical GPS), relative phase-shift in real-time (single station RTK), and compensated relative phase-shift in real-time (network RTK). Real-time GPS is beneficial for navigation and movement, while non real-time GPS requires long stationary periods for precise centimeter accuracy.
Ortho-correction: Ortho-correction compensates for perspective shifts in aerial imagery by projecting onto a concave surface. This removes perspective distortions for accurate measurements.
Map vs. Map-like Depiction: Formal maps adhere to cartographic conventions, while map-like depictions prioritize visual representation and analysis (e.g., subway maps, cartograms). Maps display features referencing terrestrial locations and charts for maritime locations. Reference maps present features, and thematic maps show specific attributes or themes (e.g., malaria spread).
Inverse Distance Weighted Interpolation: This method assigns weights to surrounding data points inversely proportional to their distance. Isotropic interpolation assumes no directional bias, weighting points equally across all directions.
Highway Route Planning (GIS): Planning a highway involves considering factors like existing road networks, urban centers, nature reserves, topography, and hydrography. The objective is a balanced approach that considers political and social factors. Data sources from a project map-base are required to encompass decision factors, with thematic information.

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Description

This quiz covers essential concepts in Geographic Information Systems (GIS), focusing on geographic datums, representation methods like raster and vector, and spatiotemporal changes. Test your understanding of how these elements play a crucial role in solving geographic problems and managing spatial data effectively.