Geographic Data Representation in GIS
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Questions and Answers

Which of the following best describes the primary function of the Image Data Model?

  • Represents physical attributes of features
  • Records electromagnetic reflectance values for each pixel (correct)
  • Captures relationships between discrete objects
  • Analyzes land cover and elevation

The raster data model captures relationships between objects.

False (B)

What is the range of digital values typically recorded in the Image Data Model for each band of spectral data?

0 to 255

The Image Data Model is primarily used in __________ and aerial photography.

<p>remote sensing</p> Signup and view all the answers

Match the data model to its characteristic:

<p>Vector Data Model = Ideal for discrete objects with defined boundaries Raster Data Model = Best for continuous data and spatial phenomena Image Data Model = Records spectral reflectance for remote sensing</p> Signup and view all the answers

Which characteristic is unique to the Image Data Model when compared to vector and raster data models?

<p>Spectral reflectance intensities (A)</p> Signup and view all the answers

The Image Data Model provides detailed descriptions of physical features.

<p>False (B)</p> Signup and view all the answers

Name one application of the Image Data Model.

<p>Remote sensing</p> Signup and view all the answers

What is the first step in representing geographic data in GIS?

<p>Identifying a real-world entity or event (B)</p> Signup and view all the answers

The vector data model represents the world as a continuous field.

<p>False (B)</p> Signup and view all the answers

What are the three types of features represented in the vector data model?

<p>Points, Lines, Polygons</p> Signup and view all the answers

The raster data model represents the world as a ______ of cells.

<p>grid</p> Signup and view all the answers

Which of the following is a key characteristic of the raster data model?

<p>Cells must be rectangular and have a fixed number of rows and columns (A)</p> Signup and view all the answers

Match the following data models with their characteristics:

<p>Vector Data Model = Represents discrete objects with fixed spatial locations Raster Data Model = Represents the world as a continuous field of variables Topology = Captures spatial relationships between objects Attribute Value = Assigned to each cell in the raster model</p> Signup and view all the answers

Only one attribute per raster dataset is permitted.

<p>True (A)</p> Signup and view all the answers

What type of applications is the vector data model best suited for?

<p>Mapping features with clear boundaries</p> Signup and view all the answers

Which of the following best describes the vector data model?

<p>Represents the world as discrete objects with fixed spatial locations. (B)</p> Signup and view all the answers

Which of the following features is NOT represented in the vector data model?

<p>Rectangles (A)</p> Signup and view all the answers

What is a key characteristic of raster data models?

<p>Uses a fixed structure of rows and columns. (B)</p> Signup and view all the answers

Which application is best suited for the raster data model?

<p>Land cover classification (D)</p> Signup and view all the answers

How does the choice of data model impact geographic data representation?

<p>It affects how spatial relationships and attributes are captured. (C)</p> Signup and view all the answers

What type of spatial features are represented by points in the vector data model?

<p>Single locations with no length or area (A)</p> Signup and view all the answers

Which statement about raster data is correct?

<p>Spatial resolution is influenced by cell size. (A)</p> Signup and view all the answers

What is a primary characteristic of the Image Data Model?

<p>Stores spectral reflectance intensities for each pixel. (C)</p> Signup and view all the answers

Which statement accurately describes the attribute representation in the Image Data Model?

<p>It provides only spectral reflectance values without additional attributes. (A)</p> Signup and view all the answers

What distinguishes the Image Data Model from the Raster Data Model?

<p>Image Data Model often lacks detailed physical feature descriptions. (A)</p> Signup and view all the answers

In what applications is the Image Data Model primarily utilized?

<p>Remote sensing and aerial photography. (A)</p> Signup and view all the answers

How do pixels in the Image Data Model store information?

<p>By recording spectral reflectance intensities for each pixel. (B)</p> Signup and view all the answers

Which aspect of the Image Data Model helps in creating new data through digitization?

<p>Providing visual context based on reflectance. (C)</p> Signup and view all the answers

What does the term 'pixel' in the context of the Image Data Model refer to?

<p>The smallest unit, storing electromagnetic values. (C)</p> Signup and view all the answers

Which characteristic is true for both the Raster and Image Data Models?

<p>Both utilize pixels with X, Y coordinates. (C)</p> Signup and view all the answers

Flashcards

Geographic Data Representation

The process of turning real-world features and events into digital information that a GIS can understand.

Data Model Selection

Choosing how to simplify real-world features, based on what traits are important, before representing them digitally.

Vector Data Model

Represents the world as individual objects with distinct locations and boundaries.

Points (Vector)

Represent locations with no length or area, like a single tree.

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Lines (Vector)

Represent features with length but no area, like a river.

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Polygons (Vector)

Represent areas with closed boundaries, like a lake or a country.

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Raster Data Model

Represents the world as a continuous field of values, divided into a grid of cells.

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Cell Value (Raster)

The value assigned to each cell in a raster, representing a property like elevation or temperature.

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Image Data Model

A data model that records electromagnetic reflectance values for each pixel, representing spectral information instead of physical attributes.

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Pixel

A basic unit of an image, representing a specific area and storing spectral reflectance intensities.

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Reflectance Values

Numerical values representing the amount of electromagnetic radiation reflected by a surface, ranging from 0 (no reflection) to 255 (full reflection) for each spectral band.

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Spectral Bands

Different ranges of electromagnetic radiation captured by sensors, corresponding to specific wavelengths of light.

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Remote Sensing

The process of acquiring information about an object or area from a distance, often using sensors on satellites or aircraft.

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Digitizing Features

Converting real-world features into digital representations, using images as a source for data creation.

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Raster Data Model vs. Image Data Model

While both use a grid-like structure, the Raster Data Model focuses on physical attributes (e.g., elevation), while the Image Data Model uses reflectance values for remote sensing information.

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Image Data Model Applications

Remote sensing, aerial photography, and creating new data by digitizing features are common applications of the Image Data Model.

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Point Features

Vector data that represents single locations in space with no length or area, such as trees.

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Line Features

Vector data that represents one-dimensional objects with length but no area, such as rivers or roads.

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Polygon Features

Vector data that represents two-dimensional objects with a definable area, such as lakes, forests, or countries.

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Spectral Reflectance

The amount of light a surface reflects at different wavelengths. Recorded as values in each pixel, representing how the object 'looks' at different colors of light.

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Digital Number

The number assigned to a pixel's spectral reflectance value, ranging from 0 (no reflection) to 255 (full reflection).

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Image Data Model vs. Raster Data Model

Both use a grid-like structure, but image data stores spectral reflectance values for remote sensing applications, while raster data stores physical attributes like elevation.

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Study Notes

Geographic Data Representation in GIS

  • GIS represents real-world spatial entities or events digitally.
  • Data model selection depends on desired characteristics and abstractions.
  • Chosen models translate into suitable structures for computer processing.
  • Model choice affects how real-world complexities are depicted.
  • Vector data models show objects with fixed location.
    • Points represent locations (e.g., trees).
    • Lines represent features with length (e.g., rivers).
    • Polygons represent features with area (e.g., lakes, land).
    • Attributes describe objects (e.g., land parcel type).
    • Topology captures spatial relationships (e.g., river flows into lake).
    • Use for features with clear boundaries (census tracts, roads).
  • Raster data models represent a continuous field as a grid of cells.
    • Each cell stores one attribute value (e.g., elevation, land cover).
    • Uniform rectangular shape, fixed rows and columns.
    • Spatial resolution affects detail.
    • Used for areas like elevation maps, land cover, temperature.
  • Image data models store electromagnetic reflectance.
    • Pixels represent spectral reflectance intensities.
    • Pixel properties include spatial coordinates and resolution.
    • Values range from 0 to 255 per band.
    • Used in remote sensing, photography, and digitization.
    • Electromagnetic reflectance is stored; physical attributes are not stored directly.

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Related Documents

GIS Lecture 2a Notes PDF

Description

Explore how Geographic Information Systems (GIS) represent real-world spatial entities through different data models. This quiz covers vector and raster models, their structures, and the attributes associated with spatial features. Test your knowledge on how these representations influence the understanding of real-world complexities.

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