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Fundamentals of GIS > GIS Final Exam > Flashcards

GIS Final Exam Flashcards

1
Q

What does a raster model do?

A

It uses an array of values in cells/pixels representing squares on the ground

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2
Q

What does the cell value correspond to?

A

the characteristic of the spatial phenomenon at the cell location

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3
Q

What is raster data BEST suited for representing?

A

Continuous Phenomena

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4
Q

What is a corner cell assigned with:

A

X-Y Coordinate pairs.

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5
Q

What do columns represent in GIS

A

X coordinate

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6
Q

What do rows represent in GIS

A

Y coordinate

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7
Q

What does cell size determine?

A

The resolution of a raster

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8
Q

What does it mean if the cell size is smaller?

A

The resolution is higher

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9
Q

What is required if the cell size is smaller and the resolution is higher?

A

More cells are required to cover the same area, requiring a larger file size

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10
Q

What does each cell contain?

A

ONE numeric value (like integers or floating points)

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11
Q

What do numeric values found in cells correspond to?

A

One specific characteristic or spatial phenomenon

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12
Q

What are the advantages of raster?

A

-provides a simple data model
-makes for easy data collection
-is better at analyzing certain types of data
-often has faster analysis than vectors
-imagery is desirable for certain maps

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13
Q

What are the 3 types of raster data

A

Thematic, images, and indexed color raster

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14
Q

What is continuous raster?

A

Presents quantities/variables that change over the earth’s surface (precipitation, elevation, population density, temperature etc.). This means that neighboring cells often have different values to show continuous change over space.

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15
Q

What does a discrete raster do?

A

Stores vector type features in a raster format. This means that neighboring cells usually have the same values, but they can change suddenly at the borders.

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16
Q

What format are cell values usually in in a discrete raster?

A

Integer

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17
Q

What is an image raster?

A

A raster that stores reflectance of electromagnetic radiation from earth’s surface as its values.

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18
Q

What is a raster pyramid and why is it needed?

A

They are a way for a raster to speed its display. It takes little time and increases the storage size by about 50%.

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19
Q

What is raster resampling?

A

The process of recalculating and assigning the cell size/orientation of a raster.

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20
Q

What is block resampling?

A

Category values (majority, central cell), numeric values (average, medium, minimum),

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21
Q

in GENERAL RESAMPLING, what is the nearest neighbor method?

A

uses the value from the original cell falling at the center of the new one

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22
Q

in GENERAL RESAMPLING, what is the area-weighted average

A

area-based averaging of the involved
original cells

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23
Q

in GENERAL RESAMPLING, what is the bilinear interpolation

A

distance based averaging of the 4 nearest original cells

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24
Q

in GENERAL RESAMPLING, what is the cubic convolution?

A

weighted avg of the 16 nearest original cells.

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25
Q

What are the 2 parts of the raster file:

A

Header and Number array

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26
Q

What is the header in the raster file?

A

provides the information about the file, such
as the number of rows and columns, coordinate system

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27
Q

What method is used to reduce raster storage size?

A

Compression

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28
Q

In raster compression, what is the lossless method?

A

Includes run-length encoding and quad trees.

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29
Q

What does the run-length method of the lossless method do?

A

stores the number of cells and the cell value of each run?

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30
Q

What does the quad tree method of the lossless method do?

A

divides the area, step by step, into quadrants until it becomes homogenous with each quadrant. See the spatial indexing system on the first file.

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31
Q

What is implicitly stored in a raster?

A

Location information

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32
Q

How many times should projecting raster be done, and why?

A

As few times as possible. It takes more memory and may introduce artifacts.

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33
Q

How is a georeferencing raster done?

A

-Scanned maps have a cs in pixels and must be georeferenced
-Users identify pairs of ground control points visible in the raster and in a reference dataset
-a transformation then calculates the real world coordinates from the control point pairs and applies it to the raster.

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34
Q

In georeferencing, what is an affine transformation?

A

Linear transformation involving translation, rotation, scaling, and shearing

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35
Q

What is the MINIMUM number of points that affine transformation requires?

A

three

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36
Q

In georeferencing, what is a second/third order polynomial?

A

-It allows stretch or contact
-Additional points are needed

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37
Q

Does raster data explicitly store x-y coordinates for every cell?

A

No

38
Q

What does raster overlay do?

A

Applies cell-by-cell operations on a stack of aligned cells to conduct the analysis.

39
Q

What does map algebra do?

A

combine 2+ layers to produce a new raster layer.

40
Q

What are some map algebra operations?

A

Arithmetic functions, statistical functions, boolean operations, etc.

41
Q

How are Rasters first converted to boolean rasters?

A

Via logical functions for boolean overlay operations

42
Q

What are the ONLY possible values for a boolean raster?

A

True or False

43
Q

How is raster boolean overlay performed?

A

On a cell-by-cell basis

44
Q

What happens in a weighted overlay?

A

-Input rasters (R) are ranked, which have scaled values and represent different conditions.
-A weight (W) is then assigned to each raster to indicate its relative importance. The weights must sum to 1.

45
Q

Where do local operations process?

A

On a single cell from each raster at a time

46
Q

What does a neighborhood (focal) operation use?

A

A focal cell and a set of its surrounding cells for the calculation

47
Q

where do zonal operations apply

A

to a zone defined by a group of cells of the SAME values.

48
Q

What does a global operation do?

A

Performs a computation on the raster as a WHOLE.

49
Q

What can a global operation do?

A

Measure physical distance, allocation and direction.

50
Q

What mathematical functions can be used in a local operation?

A

Arithmetic, logarithmic, trigometric, etc.

51
Q

In a LOCAL operation, what does reclassification do?

A

Creates a new raster by classification

52
Q

What is spatial interpolation?

A

The process of using points with known values to estimate values at other points.

53
Q

the number and distribution of sampling points can influence:

A

The accuracy of spatial interpolation

54
Q

What does systematic sampling look like?

A

Even distribution/even rows

55
Q

What does random sampling look like?

A

Random dots

56
Q

What does adaptive sampling do?

A

Makes the dots cling to object

57
Q

What is tobler’s law?

A

Everything is related to everything else, but near things are more related than distant things

58
Q

One common interpolation method is IDW. What does it stand for?

A

Inverse Distance Weighted.

59
Q

What does Inverse Distance Weighted interpolation do?

A

Gives greater weights to points closest to the prediction location, and the weights diminish as a function of the distance.

60
Q

What does Inverse Distance Weighted interpolation do?

A

Gives greater weights to points closest to the prediction location, and the weights diminish as a function of distance. A specified number (or all) points can be used to determine the output value for each location

61
Q

What does the spline method do?

A

Estimates values using a mathematical function that minimizes overall surface curvature, resulting in a smooth surface that passes exactly through the input points.

62
Q

What is the spline method best used for?

A

Gently varying surfaces like elevation, water table heights, or pollution concentrations

63
Q

How is IDW method different from spline method

A

In IDW, the contour lines are LESS smooth, and the peaks and valleys form at extreme values in the same sample data.

64
Q

What is density estimation?

A

A function that counts the number of features within a specified circle and divide by the circle area to yield a density value.

65
Q

What is a simple density function?

A

Function that assumes that the weight value occurs exactly AT THE FEATURE LOCATION

66
Q

What does a kernal density function do?

A

Spreads the value over an area using a distribution function before counting?

67
Q

Slope is a surface analysis tool. What does it do?

A

Measures the rate of elevation change at a surface location

68
Q

What are the two forms that slope can be reported in?

A

Degree or percent

69
Q

What is the aspect of a slope?

A

the direction of the steepest slope

70
Q

How is aspect expressed

A

In an azimuth angle from 0 to 360, where North= 0, and flat areas are assigned a value of -1

71
Q

What does a Hillshade analysis tool do?

A

Depicts the brightness of terrain reflections given a terrain surface and an illumination source that is placed at a designated azimuth and zenith angle

72
Q

what does a viewshed do?

A

Shows the areas that are visible from a set of designated observation points

73
Q

What does the cut and fill analysis tool do?

A

Determines HOW MUCH material is LOST OR GAINED in a study area by comparing two surface models of the area. One before a change and one after the change.

74
Q

What does editing refer to in GIS?

A

Updating existing feature classes, or creating new ones, including BOTH spatial AND attribute information

75
Q

What are some editing tools to maintain topology?

A

Snapping to avoid dangles: point endpoint, edge, and vertex snapping.
-and creating coincident polygon boundaries: autocomplete polygon construction tool and split tool

76
Q

Sketches:

A

Provisional features used when creating or modifying shapes in ArcGIS pro.

77
Q

Map topology:

A

Construct in arcgis to automatically track features that are adjacent or connected to each other.

78
Q

In Sharing GIS, what is a workflow?

A

A sequence of data management or analysis steps needed to complete a task.

79
Q

What are the 3 ways to share workflows in ArcGIS

A

ModelBuilder
Scripts
Tasks

80
Q

What does modelbuilder do?

A

A graphic canvas used to string tools and inputs in a sequence for automatic execution

81
Q

What is a script?

A

Programs written in computer languages

82
Q

What is a task?

A

Workflow that permits a user to make decisions/interact with the workflow as needed.

83
Q

What is metadata

A

Data about data.

84
Q

What defines quality data?

A

The fitness of a dataset for a given purpose

85
Q

One data quality issue is lineage. What is its definition?

A

Where did it come from, and how was it processed?

86
Q

One data quality issue is positional accuracy. What is its definition?

A

Are features in the right location?

87
Q

One data quality issue is attribute accuracy. What is its definition?

A

Are the attributes in the table correct?

88
Q

What is logical consistency?

A

How well are the real-world relationships configured in the data.

89
Q

One data quality issue is completeness. What is its definition?

A

Was every instance recorded or every measurement taken>

90
Q

One data quality issue is temporal accuracy. Definition?

A

How long will the dataset remain valid, and are there any regular updates planned?

Fundamentals of GIS (6 decks)

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