Exame GIS
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Questions and Answers

Which of the following is an advantage of vector data in GIS?

  • Relatively large storage requirement
  • Ability to handle multiple attributes for each object (correct)
  • Can store continuous surface data
  • Lack of topology
  • Raster data is capable of representing fuzzy objects.

    True (A)

    Name two disadvantages of using raster data in GIS.

    Limited precision and its large file size

    A key advantage of using a secant map projection over a tangential projection is that it _______ projection distortion.

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

    Match the following GIS methods to their appropriate characteristics:

    <p>Raster = Large storage requirements Vector = Well-defined topology</p> Signup and view all the answers

    What does a local ellipsoid approximate in relation to the geoid?

    <p>The local curvature of the geoid (D)</p> Signup and view all the answers

    What is a spatiotemporal scenario in GIS?

    <p>Spatial change over time</p> Signup and view all the answers

    Vector data is incapable of representing continuous phenomena.

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

    What is a primary advantage of network RTK over single-station RTK?

    <p>Provides spatially varying compensation for positional errors (B)</p> Signup and view all the answers

    SWEPOS is a global network of positional reference stations.

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

    Explain the role of GPS satellites in single-station RTK.

    <p>GPS satellites provide positional data in conjunction with a GPS transmitter at a known reference position.</p> Signup and view all the answers

    A _____ map uses polygons to represent data with constant attribute values.

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

    Match the following with their respective definitions:

    <p>Choropleth Map = A map using polygons to show attribute values Multivariate Representation = Symbols carrying multiple attribute values Cartogram = A map that distorts area or distance for specific objectives</p> Signup and view all the answers

    Which of the following is an example of a passive sensor?

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

    Active sensors, like radar, emit their own signals to collect data.

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

    What is the significance of ionic activity in network RTK?

    <p>Ionic activity is a source of atmospheric positional error that network RTK aims to compensate for.</p> Signup and view all the answers

    What is the primary purpose of secant projections in cartography?

    <p>Reduce distortion by allowing the paper to cut through the surface (C)</p> Signup and view all the answers

    In a tangential projection, the paper touches the Earth along two meridians.

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

    What geographic features does a typical 1:50,000 terrain map include?

    <p>Land-cover, topography, infrastructures, urban structure, hydrology</p> Signup and view all the answers

    The referential skeleton of a terrain map in non-arid regions typically includes features like _____ and urban structures.

    <p>water bodies</p> Signup and view all the answers

    Match the following map types with their characteristics:

    <p>Terrain map = Contains land-cover and topography Topographic map = Displays elevation and contour lines General map = Overview of a large area without detailed features Thematic map = Focuses on specific themes like population or climate</p> Signup and view all the answers

    What happens to the scale in a secant projection compared to the tangent meridian?

    <p>It can be less than, equal to, or greater than 1:1 (D)</p> Signup and view all the answers

    The central meridian in a secant projection coincides with the tangent meridian.

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

    The average projection error is _____ in secant projections compared to tangential projections.

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

    Flashcards

    Secant Projection

    A map projection where the projection paper cuts through the Earth's surface, minimizing average scale error.

    Tangential Projection

    A map projection where the projection paper touches the Earth's surface along a meridian.

    Central Meridian

    The line of longitude used as the reference point in a map projection.

    1:50,000 Scale Map

    A common scale for detailed reference maps, showing a large amount of detail.

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    Referential Skeleton (Map)

    Key features on a map used for orientation and reference (e.g., water bodies, roads).

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    Terrain Map Content

    A terrain map shows land cover, topography, infrastructure, urban areas, and hydrology.

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    Secant Cylinder Projection

    Cylindrical projection where the projection cylinder cuts through the Earth at two points.

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    Transversal Cylindrical Projection

    Cylindrical projection rotated to follow the central meridian of a particular region.

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    Network RTK

    A differential GPS method that uses multiple reference stations to compensate for atmospheric errors, like ions and electrical conductivity, to improve positioning accuracy.

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    Single-station RTK

    A differential GPS method using one reference station for positioning, often less accurate than network RTK due to reliance on a single reference point.

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    SWEPOS

    The national Swedish network of positional reference stations used in various differential GPS methods.

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    Choropleth Map

    A map where polygons (like counties/regions) represent a single constant attribute value like population density or another attribute.

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    Multivariate Representation

    A map where symbols carry different attribute values, rather than representing just one. For example, the speed and direction of a current.

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    Cartograms

    Maps that distort area or distance to emphasize an attribute (rather than showing actual geographic areas accurately).

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    Passive Sensor (Remote Sensing)

    A sensor that relies on external light sources, like the sun, to gather information.

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    Active Sensor (Remote Sensing)

    A sensor that emits its own signals (like radar or sonar) to bounce back for data collection.

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    Raster Data Advantages

    Raster data is simple to structure, can store continuous surfaces like temperature, and represents fuzzy objects like wetlands. It's good for visualizing continuous phenomena like elevation.

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    Raster Data Disadvantages

    Raster data lacks topology (spatial relationships between features), requiring large storage space, and can lead to inaccuracies when representing precise shapes.

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    Vector Data Advantages

    Vector data has exact geometry, accurately represents shapes, can store multiple attributes for each object, and defines spatial relationships with topology, thus representing connectivity and adjacency.

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    Vector Data Disadvantages

    Vector data can be computationally complex for analysis, lacks representation of continuous phenomena, and may be overly precise in some contexts, lacking data for regions.

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    Representing Spatiotemporal Change

    Spatiotemporal data reflects how geographic features change over time. Use raster data to gather temporal snapshots during change periods (monthly, yearly, or seasonal) to visualize change.

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    Geoid and Local Ellipsoid

    The geoid is a gravity-based surface approximating Earth's shape. To capture local gravity, a local ellipsoid is used to approximate local curvature of the geoid, maintaining the connection to the global ellipsoid while providing a mathematically defined surface.

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    Advantages of Secant Projection

    Secant projections minimize average scale error compared to tangential projections, as the projection cylinder cuts through the Earth at two points.

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    Secant vs. Tangential Projections

    Secant projections provide a balance of accuracy across a larger area by minimizing average scale error, while tangential projections are more accurate at the point of tangency but have higher distortion elsewhere.

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    Study Notes

    Geographic Problems in GIS

    • Geographic problems involve location, either in the information or the solution itself.
    • Examples include forest management, precision farming, and navigation.
    • Categorizing geographic problems is important due to their wide variety.

    Methods for Categorizing Geographic Problems

    • Scale: Defines the level of detail, including micro (e.g., crystalline structures), local (cities), regional (wide-spread epidemics), and global (pandemics).
    • Intent/Purpose: Categorization based on goals. Examples include practical/urgent needs (emergency, money), and curiosity-driven investigations (continental plate movement).
    • Time-Scale: Categorization based on the timeframe of the problem. Examples include operational tasks (everyday organizational functions), tactical planning (short-term plans), and strategic goals (long-term objectives).

    Geographic Data (Datum)

    • A datum contains a geographic position and its associated attribute value.
    • A geodetic datum defines the position, and an attribute defines the associated descriptive property.
    • Geographic attributes are classified in relation to their scale type.

    Geographic Data Representation

    • Raster: Information is regulated by pixel size.
    • Vector: Information is regulated by the number of points an object is given.

    Simplifying Geographic Reality

    • Tessellation (Spatial Averaging): Simplifies reality by deciding pixel (density) size. More detail increases the number of pixels, while less detail decreases the number of pixels.
    • Constant-Value: Simplifies large areas with similar attributes into a single value; e.g., the entire ocean could be given one value as the majority of an attribute is constant.

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    Description

    This quiz explores the categorization of geographic problems in Geographic Information Systems (GIS). It covers various methods to categorize these issues, including scale, intent, and time-scale. Additionally, it highlights the significance of geographic data in solving complex spatial challenges.

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