Vector Raster

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Questions and Answers

In a GIS, what is the primary difference in how vector and raster data structures represent spatial information in urban analysis?

Vector data represents geographic features with points, lines, and polygons, while raster data represents continuous fields or discrete objects as an array of cells (pixels). (correct)
Vector data models continuous fields, whilst raster data represents discrete objects.
Vector data uses pixels to represent geographic features, while raster data uses points, lines, and polygons.
Vector data is used for analysis, and raster data is only used for visualization.

When analyzing urban heat islands using GIS, which data structure, vector or raster, would be most appropriate for representing temperature variations across the city and why?

Vector, because it allows for precise calculation of temperature averages within specific administrative regions.
Raster, because it can efficiently store and display continuous temperature data as a grid of values. (correct)
Vector, because it can accurately represent the boundaries of different temperature zones.
Raster, because it enables the creation of detailed 3D models of urban buildings for thermal analysis.

A city planner needs to identify areas prone to flooding. How could both vector and raster data be used to model flood risk, and what role would each data structure play?

Vector data would represent elevation, while raster data would define the boundaries of water bodies.
Vector data would represent property boundaries, while raster data would show population density.
Vector data could represent infrastructure like storm drains, while raster data could model flood depth based on elevation and rainfall data. (correct)
Vector data would map building footprints, while raster data would model hydrological flow accumulation.

Consider a project aimed at optimizing the placement of new bus stops in a city. How could vector and raster data be integrated to inform this decision?

Use vector data for bus routes and raster data for land use types, to determine optimal locations based on proximity to residential areas. (C) Signup and view all the answers

Which of the following scenarios would benefit most from using a vector data structure over a raster data structure in a GIS for urban planning?

Representing individual buildings and their precise locations. (C) Signup and view all the answers

Which data model explicitly represents spatial relationships between geographic features?

Topological vector data model (D) Signup and view all the answers

In a vector environment, what is an 'undershoot' error?

A line that falls short of connecting to its intended node. (C) Signup and view all the answers

Which of the following is a characteristic of a topological data model?

Explicitly encoding relationships like adjacency and connectivity. (B) Signup and view all the answers

What type of error in a vector dataset is represented by a line that extends past its intended intersection point?

Overshoot (B) Signup and view all the answers

Why are topological relationships important in vector data?

They allow for efficient spatial analysis and network tracing (C) Signup and view all the answers

Which of the following errors in a vector environment would most likely result in incorrect area calculations?

An undershoot (A) Signup and view all the answers

What distinguishes a topological vector model from a non-topological vector model?

The topological model stores explicit spatial relationships, while the non-topological model does not. (B) Signup and view all the answers

In the context of vector data correction, what is the significance of identifying 'pseudo nodes'?

They may be acceptable depending on the specific application and data structure. (B) Signup and view all the answers

Which of the following is NOT typically associated with raster data?

Nodes and arcs (A) Signup and view all the answers

If a GIS analyst finds a polygon with a missing label, what does this likely indicate?

The polygon has no associated attribute information (C) Signup and view all the answers

In a vector environment, what is the primary purpose of automatically closing a polygon?

To ensure correct area and perimeter calculations. (A) Signup and view all the answers

What does the term 'dangling lines' refer to in the context of vector data editing?

Lines that do not connect to other lines, forming incomplete or broken segments. (D) Signup and view all the answers

How does linking graphic elements to alphanumeric attributes enhance data analysis in a GIS environment?

It enables querying and analysis based on descriptive characteristics. (D) Signup and view all the answers

What benefit does importing an external database with a key attribute provide in a GIS project?

It allows linking spatial data with non-spatial information for enhanced analysis. (A) Signup and view all the answers

What is the key difference between airborne orthophotos and satellite remote sensing data?

Airborne orthophotos generally offer higher spatial resolution than satellite data. (B) Signup and view all the answers

Which of the following is an example of a DTM (Digital Terrain Model) data format?

Raster data in grid format (C) Signup and view all the answers

How do 'undershoot' and 'overshoot' errors typically manifest in vector data and what is their impact?

They lead to gaps or overlaps in line features, affecting topological integrity and spatial analysis. (B) Signup and view all the answers

What is the significance of interactive data entry in a vector environment for each graphic element?

It allows for immediate attribute assignment and verification, ensuring data accuracy. (A) Signup and view all the answers

Which of the following best describes the primary difference between a subway map and a topographic map?

A subway map prioritizes topological relationships, while a topographic map aims for faithfulness to reality. (C) Signup and view all the answers

What is a 'sliver' in the context of topological errors in vector GIS?

A spurious area resulting from the duplicated digitization of an arc. (A) Signup and view all the answers

Which topological error is most likely to result in a non-closed polygon?

Pseudonode. (D) Signup and view all the answers

What does an adjacency matrix represent in the context of GIS topology?

The connectivity between different areas. (A) Signup and view all the answers

What is the primary cause of topological ambiguities during raster-to-vector conversion?

The inherent differences in data structure between raster and vector formats. (D) Signup and view all the answers

In a connectivity matrix, what information is typically stored?

The presence or absence of a connection from node to node. (D) Signup and view all the answers

Which topological error is characterized by a line extending beyond its intended intersection point?

Overshoot. (C) Signup and view all the answers

How do tolerances affect topological cleaning in vector GIS?

Tolerances define the acceptable level of error when snapping vertices together. (D) Signup and view all the answers

What is the purpose of managing topological relationships in a vector system?

To ensure data integrity and enable spatial analysis. (A) Signup and view all the answers

Considering topological relationships, which matrix would be most useful for determining what is to the left and right of a river?

Side matrix. (A) Signup and view all the answers

When converting a raster to vector, what makes this process more challenging compared to vector-to-raster conversion?

It involves inferring shapes and boundaries, potentially increasing data complexity. (B) Signup and view all the answers

In a scenario where a raster cell represents temperature values, what would the cell's value of 22.5 likely signify?

A direct measurement of temperature recorded at that location. (D) Signup and view all the answers

How does the 'winner takes all' approach handle mixed pixels in raster data?

By assigning the value of the dominant land cover type within the pixel. (D) Signup and view all the answers

When dealing with remote sensing imagery represented as raster data, what do the integer values (Digital Numbers - DN) of each cell (pixel) primarily correspond to?

Reflectance characteristics of the surface area captured by the pixel. (A) Signup and view all the answers

In the context of raster data, what is the primary function of a Value Attribute Table (VAT)?

To link numerical cell values with descriptive attributes, providing additional context. (B) Signup and view all the answers

Why is it generally recommended to maintain data in its original format (either raster or vector) whenever possible?

To prevent the loss of data integrity and precision during format conversions. (D) Signup and view all the answers

What is the 'mixed pixel' problem in raster data typically referring to?

Pixels that contain multiple types of features or land cover within their area. (A) Signup and view all the answers

In rasterization, what is the primary method for assigning values to pixels when converting from vector data?

Overlaying a grid on the vector map and determining the presence or absence of vector entities within each pixel. (D) Signup and view all the answers

What is a common method for vectorizing a raster entity?

Tracing along the outer edges or the centerlines of the raster pixels. (B) Signup and view all the answers

A raster cell's value is modified from 5 to 9 to represent an urbanized area instead of a wooded area. What does this modification primarily illustrate?

The thematic classification scheme of the raster dataset is being altered. (D) Signup and view all the answers

Which of the following is an advantage of the vector data model over the raster data model?

Compact data structure and faithful representation of real phenomena. (B) Signup and view all the answers

A city planner needs to analyze traffic flow on a road network. Which data model, vector or raster, is more suitable for this task, and why?

Vector, because it efficiently codes topological relationships necessary for network analysis. (D) Signup and view all the answers

Which of these statements accurately describes a key difference regarding spatial variability between raster and vector data?

Raster models are efficient for describing data with high spatial variability, while vector models represent distinct features. (D) Signup and view all the answers

What is a primary disadvantage of using a raster data model to represent geographic data?

Non-compact structure leading to potentially large data volumes. (B) Signup and view all the answers

Which of the following describes a vertex in the context of a vector data model?

An intermediate point defining the shape of a line or polygon. (D) Signup and view all the answers

In which scenario would a raster data model likely be preferred over a vector data model?

Modeling elevation changes in a mountainous region. (A) Signup and view all the answers

What is a significant limitation of the vector data model regarding overlay operations?

Complexity in carrying out overlay operations. (A) Signup and view all the answers

Consider a project that requires integrating satellite imagery with existing GIS data. Which data model, raster or vector, would facilitate simpler integration, and why?

Raster, due to the immediate integration of remote sensing data. (D) Signup and view all the answers

When might converting between vector and raster data models need careful evaluation?

When maintaining accuracy and topological relationships is crucial. (B) Signup and view all the answers

What type of geographic feature is least suited for representation using a raster data model?

Precise boundaries of individual buildings in a downtown area. (B) Signup and view all the answers

In the context of vector data models, what is the significance of 'topological relationships'?

They encode the spatial relationships between features, such as adjacency and connectivity. (D) Signup and view all the answers

Which characteristic is the least significant factor when choosing between raster and vector data models for a GIS project?

The availability of specialized GIS software. (C) Signup and view all the answers

How does the representation of spatial features differ between vector and raster data models?

Vector models represent features as points, lines, and polygons, while raster models use grid cells. (C) Signup and view all the answers

What is an advantage of raster data for modeling operations?

Description of data with high spatial variability and rapid simulation and modeling operations. (D) Signup and view all the answers

What is orthophoto?

Immediate integration of remote sensing data or digital photogrammetry (D) Signup and view all the answers

Flashcards

Vector Data Structures

Methods for storing spatial data using points, lines, and polygons.

Raster Data Structures

Methods for storing spatial data using a grid of cells, each containing a value.

Geographic Information System (GIS)

A system designed to capture, store, manipulate, analyze, manage, and present spatial or geographic data.

Geomatics

The science and technology of gathering, analyzing, interpreting, distributing, and using geographic information.