What kinds of models are there (4 pairs of types)?
Descriptive vs. prescriptive
Deterministic vs. stochastic
Static vs. dynamic
Deductive vs. inductive
In GIS, what 2 things does geometric transformation include?
Map-to-map transformation
Image-to-map transformation
As a rule, what type of transformation should be used for map-to-map or image-to-map transformations?
C. Affine
True or false: equiarea transformations preserve both shape and size.
A. True
B. False
A. True
What does a similarity transformation preserve?
D. Shape
What do affine transformations preserve?
D. Parallelism of lines
Which type of transformation allows both angular and length distortions?
D. Projective
Which of the following do affine transformations permit?
I. Rotation
II. Translation
III. Skew
IV. Differential scaling.
D. All of the above.
What does Root Mean Square error measure?
The acceptability of the 6 coefficients, as estimated from the control points, following a transformation.
What are the 3 common resampling methods?
Nearest neighbor
Bilinear interpolation
Cubic convolution
Which resampling method fills each pixel of the new image with the nearest pixel value from the original image?
C. Nearest neighbor
Which resampling method uses the average of the 4 nearest pixel values from 3 linear interpolations?
D. Bilinear interpolation
Which resampling method uses the average of the 16 nearest pixel values from 5 cubic polynomial interpolations?
B. Cubic convolution
With nearest-neighbor analysis, what value must R have for the spatial features to be considered clustered?
B. Less than 1
Spatial autocorrelation determines the relationship among values of a variable according to which of the following?
A. Both
With Moran's I, there is less spatial correlation if
D. Moran's I < E(I)
What does z-score measure?
The distance between the raw score and the population mean.
What units does z-score use?
Standard deviations.
What does LISA stand for?
Local Indicators of Spatial Association; A local version of Moran's I, this method calculates the z-score for each feature. A more negative Z means that the feature is is adjacent to dis-similar features; a more positive Z means that the feature is adjacent to similar features.
With G-statistic, what does a high G(d) mean?
A. A cluster of high values.
What is the difference between local and global interpolation methods?
Local methods apply a single mathematical function repeatedly to small subsets of the total set of observed data. Global methods apply a single mathematical function to all observed data points; this generally produces smooth surfaces.
What is the difference between exact and approximate interpolation methods?
Exact methods honor all observed points for which data are available, without smoothing or altering their values. This is most appropriate if there is a high degree of certainty attached to the measurements made at the points. Approximate methods do not have to honor all the observed data points; they can smooth the points to fit the general trend; most appropriate when there is uncertainty surrounding the measurements made at the sample points.
What is the difference between deterministic and stochastic interpolation methods?
Deterministic methods are used when there is sufficient knowledge about the surface being modeled for its character to be described as a mathematical function; stochastic methods are used to handle uncertainty--random variation in the interpolated surface.
Apart from local vs. global, gradual vs. abrupt, deterministic vs. stochastic, what other classifications of interpolation methods are there?
B. Exact vs. approximate
What is kurtosis?
Kurtosis is a measure of the "peakedness" of the probability distribution of a real-valued random variable. High kurtosis means that the "bell curve" has a sharper peak and longer, thicker tails, while low kurtosis means a more rounded peak and shorter, thinner tails.
What is skewness?
Skewness is a measure of the asymmetry of the probability distribution of a real-valued random variable. A negative skew means that the tail on the left side is longer than on the right and the bulk of the values lie to the right of the mean. A positive skew means a longer tail on the right side and the bulk of the values to the left of the mean. Zero skewness implies a more-or-less symmetrical distribution.
What is the difference between the standard line and the central line?
Central lines are the central parallel and the central meridian; toghether, they define the origin of a map projection. The standard line is the line of tangency between the map and the globe; it has no distortion and has the same scale as the reference globe.
What 3 things make up a datum?
Origin
Spheroid
Separation of the spheroid and the Earth at the origin.
Why is the datum important?
It serves as the reference or base for calculating the geographic coordinates of a location.
What spheroid was used for NAD27?
The Clarke 1866 spheroid.
What spheroid is the basis for NAD83?
GRS80
What is the scale factor of each UTM zone at its central meridian?
0.9996
What is the latitude of origin of each UTM zone?
The equator.
What is the scale factor?
The normalized local scale, or the ratio of the local scale to the principal scale.
What is the principal scale?
The scale of the reference globe.
What determines the center of a map projection?
B. The central lines
What is the topological relationship of connectivity?
D. Arcs connect to each other at nodes
What is the topological relationship of contiguity?
B. Arcs have directions and left and right polygons
What is the topological relationship of area definition?
A. An area is defined by a series of connected arcs
What are 2 advantages of topology-based coverages?
Because a shared or common boundary between 2 polygons is stored in the arc-coordinate list once, the number of data entries is reduced, and it is easier to update the polygons.
What is the main advantage of using
non-topological vector data such as shapefiles?
They can display more rapidly on the computer monitor than topology-based data, and they are non-proprietary.
What does the data structure of a TIN include, apart from the triangle number and data files showing the lists of points, edges, and the x, y, and z values of each elevation point?
The number of each adjacent triangle.
What are 2 differences between the simple polygon model and the regions model?
Regions can have spatially joint or disjoint areas; polygons cannot.
Regions may overlap; polygons cannot.
What is encapsulation?
C. A principle used in object-oriented technology to hide the properties and methods of an object so that the object can be accessed only through the predefined interfaces
What is a feature class?
A data set that stores features of the same geometry type in a geodatabase.
What is a feature dataset?
A collection of feature classes in a geodatabase that share the same coordinate system and area extent.
True or false: TIGER data are topology-based.
A. True
B. False
A. True
What does instantiation mean?
It means that an object of a class can be created from an object of another class.
What file extensions do personal geodatabases have?
B. .mdb
What file extensions do file geodatabases have?
D. .gdb
What is a digitized image in which the displacement caused by camera tilt and terrain relief has been removed from an aerial photograph?
A digital orthophoto quad (DOQ).
What is a DRG?
A Digital Raster Graphic (a scanned image of a USGS topographic map).
True or false: a raster with a smaller cell size has a coarser (lower) resolution than one with a larger cell size.
A. True
B. False
B. False
True or false: The origin of rows and columns in a grid is usually in the upper-left corner of the raster.
A. True
B. False
A. True
What is the difference between a deterministic model and a stochastic model?
A stochastic model considers the presence of some randomness in one or more of its parameters or variables, but a deterministic model does not.
What are the 3 steps of the modeling process?
1. Define the goals of the model.
2. Break the model down into elements and define each element's properties and the interactions between each element in the form of a diagram.
3. Implement and calibrate the model
In the context of GIS, what does loose coupling mean?
It means the linking of a GIS to other computer programs through the transfer of data files.
What are the 3 steps for setting up the weighed linear combination method?
1. Evaluate the relative importance of each criterion against other criteria.
2. Standardize the data for each criterion.
3. Calculate the index value for each unit area by summing the weighted criterion values and dividing the sum by the total of the weights.
A model that offers prediction of what the conditions of geospatial data could be or should be is called a _________ model.
A. Prescriptive
What is pyramiding?
A common technique for displaying large raster data sets that uses resampling at different levels to produce the output raster.
Why does resampling of pixel values have to be performed following an image-to-map transformation?
In order to fill each pixel of the transformed image with a value derived from the original image.
Which transformation method is most commonly used in GIS?
A. Affine
Which resampling method is the most complex computationally?
Cubic convolution
Which resampling method usually results in the smoothest output?
Cubic convolution
Which resampling method is recommended for resampling categorical data?
Nearest neighbor
A link table used in ArcMap for georeferencing shows X Source, Y Source, X Map, and Y Map. Which pair represents the estimated location of the control point?
X Source and Y Source
True or False: In ArcMap, resampling of pixel values is included as part of the rectification process.
A. True
B. False
A. True
How many variables can be displayed in a bubble plot?
C. 3
What is the point-in-polygon operation?
An overlay operation in which the same point features in the input layer are included in the output but each point is assigned the attributes of the polygon in which it falls.
What is the difference between erase and eliminate?
Eliminate creates a new layer by removing features that meet a user-defined query expression, whereas erase removes features from the input layer.
Which overlay method uses the Boolean operation of AND?
C. Intersect
Which overlay method combines the area extents from both input maps?
A. Union
Which overlay method uses the Boolean OR connector?
C. Union
If both a spatial query and an attribute query are to be performed, which one should be performed first?
The spatial query
In raster data analysis, what is a zone?
A group of cells of same values or like features.
What are 3 methods for specifying area extent for raster analysis?
Union
Intersect
Analysis mask
Which local operation can assign a unique output value to each unique combination of cell values from multiple rasters?
Combine
True or false: "No data" is the same as zero in raster operations.
A. True
B. False
B. False
Describe two methods of selecting control points after the number of control points has been determined.
1. Use the closest known points to the point to be estimated.
2. Select known points within a circle, the size of which depends on the sample size.
How is semivariance a measure of spatial dependence?
If spatial dependence exists in a data set, known points that are close to each other have small semivariances; points that are farther apart have larger semivariances.
In kriging, what is a nugget?
The semivariance value at the distance 0 in a semivariogram.
In kriging, what is range?
The distance at which the semivariance starts to level off in a semivariogram.
In kriging, what is a sill?
The semivariance at which the leveling starts in a semivariogram.
In kriging, what is a partial sill?
The difference between the sill and the nugget in a semivariogram.
How is Delaunay triangulation related to Thiessen polygons?
Delaunay triangulation is often used to prepare Thiessen polygons. It ensures that each known point is connected to its nearest neighbors, and that the resulting triangles are as equilateral as possible. Once this is done, Thiessen polygons can be constructed by connecting lines drawn perpendicular to the sides of each triangle at their midpoints.
What is the difference between universal kriging and ordinary kriging?
Ordinary kriging assumes the absence of a drift and focuses on the spatially correlated component and uses the fitted semivariogram directly for interpolation. Universal kriging, however, assumes that the spatial variation in z values has a drift or a trend in addition to the spatial correlation between the sample points. In the first-order polynomial, M = b1xi + b2yi, M is the drift, xi and yi are the coordinates of the sampled point i, and b1 and b2 are the drift coefficients.
For what 2 reasons are polynomials of a higher order than the second generally not recommended for kriging?
Too little variation in the resdiuals for assessing uncertainty.
More bi coefficients, which must be estimated along with the weights, and thus a larger set of simultaneous equations to be solved.
What is an example of a stochastic interpolation method?
