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GIS > Lecture 8. > Flashcards

Lecture 8. Flashcards

1
Q

Spatial Predictions

A

Methods are used to estimate values at a unsampled location

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2
Q

spatial interpolation

A

is the prediction of variables at unmeasured locations, and based on a sampling of the same variables at known locations

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3
Q

Spatial interpolation rely on

A

he nearest points to estimate missing values, and use some measure of distance from known to unknown values.

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4
Q

Spatial Prediction

A

involves the estimation of variables at unsampled locations, but estimates are based at least in part on other variables

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5
Q

Core Area is chatacterized by

A

high use, density, intensity, or probability of occurrence for a variable or event

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6
Q

Core areas are defined

A

from a set of samples, and are used to predict the frequency or likelihood of occurrence of an object or event

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7
Q

what are the 2 controls in the sampling process

A

distributing locations and number of samples

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8
Q

Sampling patterns (4 types)

A

Systematic
random
cluster
adaptive

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9
Q

Systematic Sampling is when

A

Samples are spaced uniformly at fixed X and Y intervals and may not be the same in both directions

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10
Q

What are the Advantages of Systematic Sampling

A

Easy understand, and ease in planning and description.

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11
Q

What are the disadvantages of Systematic Sampling

A

All samples receive the same attention, difficult to stay on lines and may be biases

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12
Q

Random Sampling is when

A

Select points based on random number process and plot on a map

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13
Q

What are the Advantages of Random Sampling

A

Less biased

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14
Q

What are the disadvantages of Random Sampling

A

Does nothing to distribute samples in areas of high variation and location of the points may be a problematic

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15
Q

What is Cluster Sampling

A

Cluster centers are established by random or systematic means and then samples are arranged around each center on a map

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16
Q

What are the Advantages of Cluster Sampling

A

Reduced travel time

17
Q

What are the disadvantages of Cluster Sampling

A

Biased samples and prone to higher sampling error than the samples formed using other sampling methods.

18
Q

What is Adaptive Sampling

A

More sampling where there is more variability and is two stage sampling from prior knowledge

19
Q

What are the advantages of Adaptive sampling

A

More efficient, homogeneous area have few samples, better representation of variable areas.

20
Q

What are the disadvantages of Adaptive sampling

A

Need prior information on variability through space

21
Q

IN selecting a method

A

No single method has been shown to be more accurate in every application.

22
Q

Accuracy is judged by

A

difference between the measured and interpolated values at a number of withheld sample points

23
Q

Thiessen Polygon is done by

A

Draw lines connecting the points to their nearest neighbors and then find the bisectors of each line, connect then and then assign the resulting polygon the value of the center point.

24
Q

Fixed Radius (local averaging)

A

Cell values estimated based on the average of nearby samples and Samples used depend on search radius.

25
Q

Inverse Distance Weighted

A

Estimates the values at unknown points using the distance and values to nearby known points

26
Q

IDW equation

A

Zi is value of known point
Dij is distance to known point
Zj is the unknown point
N is a user selected exponent

27
Q

size of N affects________and larger N means____

A

the shape of the surface and the closer points are more influential.

28
Q

Spatial regression

A

Fitting a statistical model, a trend surface, through the measured points (typically polynomial)

29
Q

Trend surface equation

A

Z is dependent variable to be predicted at the point (X,Y).
ai values are coefficients for the predictive equation, usually estimated through a least squares statistical process
X and Y are the coordinate locations.
Q and W are independent variables measured at the point (X, Y)

30
Q

Spatial prediction

A

Based on mathematical models often built by a statistical process and Distinction between interpolation and prediction may be viewed as artificial

31
Q

Prediction Accuracy

A

using 10% of the sample and create a interpolated surface and compare to the whole sample to see accuracy prediction

32
Q

Interpolation uses

A

only the measured target variable and sample coordinates to estimate the variable at unknown locations

33
Q

Prediction uses

A

Methods address the presence of spatial autocorrelation

34
Q

Spatial prediction is more ______ than spatial interpolation.

A

General

35
Q

Estimation Exact methods

A

Theissen
IDW
Spline

36
Q

Estimation No exact methods

A

Fixed-Radius
Trend surface
Kriging

GIS (13 decks)

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