Ges 386

Front 1

Nodes

Back 1

End points of lines

Front 2

Vertices

Back 2

Point locations along a line

Front 3

Accuracy

Back 3

How close a measured value is to the true value

Front 4

Precision

Back 4

How close the measured values are to each other.

Front 5

Vector Topology

Back 5

Enforce strict connectivity and recording adjacency and planarity. Creates an intersection and places a node at each line crossing, record connectivity and adjacency. Maintains information on the relationships between and among points, lines, and polygons in spatial data. Greatly improves the speed, accuracy, and utility of many spatial data operations. Do not change: invariant property (polygon adjacency, connectivity. There is no single, uniform set of topological relationships that are included in all topological data models--> different researchers/ software vendors have incorporated different topological information on their data structures.

Front 6

Planar Topology

Back 6

Requires that all features occur on a two dimensional surface. There can be no overlaps among lines or polygons in the same layer. When planar topology is enforced, lines may not cross over or under other lines. At each line crossing there must be an intersection.

Front 7

Adjacency

Back 7

Which polygons are next to which.

Front 8

Connectivity

Back 8

Which lines connect to which.

Front 9

Topological constructs besides planarity

Back 9

Polygons may be exhaustive-no gaps, holes, or islands.

Line direction may be recorded-a "from" and "to" node are identified in each line. Directionality aids the representation of river or street networks, where there may be a natural flow direction.

Some GIS software creates and maintains detailed topological relationships in their data which results in more complex and perhaps larger data structures, but access is often faster, and topology provides more consistent "cleaner" data. Other systems maintain little topological information in the data structure, but compute and act upon topology as needed during specific processing.

Front 10

Topological Constraints

Back 10

Topology can be specified between layers when we want to enforce spatial relationships between entities that are stored in different layers. For example, property lines vs building footprints: rules may be specified that prevents building footprints from crossing property lines.

Front 11

Dangles

Back 11

Lines that do not connect to other lines. May be proscribed or limited ro be greater or less than some threshold length.

Front 12

Topological Data Models

Back 12

Often used codes and tables to record topology. Nodes and lines are given a unique identifier. Sequences of which are recorded as a list of identifiers, with point, line, and polygon topology recorded in a set of tables.

Many GIS systems are written so that topological tools are provided to ensure the creation and maintenance of topology but that the coding is not visible to users, nor directly accessible by them. Tables that these commands build are often quite large, complex, and linked in an obscure way, and therefore hidden from users.

Greatly enhance:

Many vector data operations. Adjacency analyses are reduced to a quick table look up (quick and easy)

Other spatial data operations. Network and other connectivity analyses are connected with the flow of resources through defined pathways.

Explicitly record the connections of a set of pathways and facilitate network analyses.

Overlay operations.

Front 13

Point topology

Back 13

Points are individual of each other.

Points may be recorded as individual identifiers with coordinates included and with no particular order.

Front 14

Line topology

Back 14

Includes substantial structure. At minimum, identifies beginning and ending points of each line. Variables record the topology in a table. Variables such as line identifier and starting and ending nodes for each line. Lines may be assigned a direction. The polygons to the left and right of the line are recorded.

Front 15

Polygon topology

Back 15

Defined by tables that record polygon identifiers and the list of connected lines that define the polygon. Edge lines are often recorded in sequential order. The line for a polygon form a closed loop and thus the starting node of the first line in the list also serves as the ending node for the last line in the list.

Front 16

Limitations and disadvantages to topological vector models

Back 16

Computational costs in defining the topological structure of a vector layer --> costs are modest

Software must determine the connectivity and adjacency information, assign codes, and build topological tables.

The data must be "clean". All lines must begin and end with a node, all lines must connect correctly, and all polygons must be closed. Unconnected lines or unclosed polygons will cause errors during analyses.

Human effort required to ensure clean vector data because each line and polygon must be checked and edited as needed to correct errors.

Front 17

Buffer

Back 17

Region less than or equal to a specified distance from one or more features. Can be created for point, line or area features. It is a proximity function.

Front 18

When you want to find out which counties are crossed by Route 66 you would use which of the following?

Back 18

Intersect Tool

Front 19

For a cadastral database to be topologically correct it is best if adjacent polygons:

Back 19

do not cross the cadestral layer. The cadestral layer is the property lines layer. The adjacent layers would be the buildings layer.

Front 20

Raster data models

Back 20

Elevation, mean temperature, slope, average rainfall, cumulative ozone exposure, soil moisture. Since raster data uses cells, it is used for variables that change continuously across a region.

Front 21

A raster's size is a function of

Back 21

cell size

Front 22

Referencing a Raster in ArcGIS. What tool?

Back 22

Mosiac/Mosaic to a new Raster

Front 23

A 1000 by 1000 raster which is resampled to a 10 by 10 raster would reduce the overall number of cells by

Back 23

1000*1000=1,000,000

10*10=100

1,000,000-100=

999,900 cells

Front 24

TIN Models

Back 24

Triangulated Irregular Networks. Commonly used to represent terrain heights. X Y and X points used to create triangles. Each triangle defines a terrain surface, assumed to be of uniform shape and slope. Uses some form of indexing to connect neighboring points. Triangular point connections continue reclusively. TIN's are more complicated than a raster grid. Can be more appropriate and efficient when storing terrain data in areas with variable, discontinuous or bumpy terrains. The differences in sampling densities results in more points, which results in smaller triangles in the densely sampled areas. TIN's preserve measurement at each location.

Front 25

Spatial Analysis Operations may produce

Back 25

A solution to a problem such as identify a high crime area or generate a list of roads that need repaving. The selection of the best location for a new business. An output that can be used as the input of the next operation. Slope (how steep each cell is). Aspect (slope direction). New Data layers. Spatial outputs with no geometric data attached. A scalar value. A list. A table

Front 26

Terms associated with Spatial Analysis Operations Scale

Back 26

Local, neighborhood, and global.

Front 27

When you do a ________ spatial operation you use data from a selected section of the surrounding area (but not the whole data layer)

Back 27

neighborhood

Front 28

Boolean Operation

Back 28

Associated with the terms AND, OR, and NOT.

Front 29

In Spatial Selection when you want to identify features that touch one another you would use

Back 29

Adjacency

Front 30

In Spatial Selection when you want to identify features that are within another feature class you would use

Back 30

Containment

Front 31

A spatial join

Back 31

uses location criterion to join features with no change in geometry of features. A spatial join involves matching rows from the Join Features to the Target Features based on their relative spatial locations.

Front 32

Which vector overlay function works like a “cookie cutter”

Back 32

Clip

Front 33

Slivers are

Back 33

areas where overlap or edges don’t meet. the overlaps are where there are topological errors, or layers that do not align exactly

Front 34

Network analysis can be used for

Back 34

roads, power lines, telephone cables, water distribution systems, and stream networks.

Front 35

Geocoding

Back 35

Spatially referencing point features based on the address of a feature and knowledge of an address range for the linear network

Front 36

By using GIS and eliminating left turns UPS reduced it’s miles traveled by

Back 36

28.5 million miles per year

Front 37

Geocoding tends to work poorest in

Back 37

rural or less developed areas

Front 38

Fixed weighting (local averaging)

Back 38

Smoothes data, gives search radii, gives a moving average.

Front 39

“The Further a Sample Point is Away, the Less Influence on Interpolated Points” This statement is associated with which of the following

Back 39

IDW

Front 40

Which of the following is not considered an Operation in Cartographic Modeling

Back 40

a flowchart

Front 41

An 8 bit single ban raster will give you

Back 41

256 potential unique values

Front 42

Which of the following raster resampling technique is best for Continuous Surfaces

Back 42

Bilinear interpolation or cubic convolution

Front 43

ArcMap can only display ____ of a multi band raster

Back 43

3 Bands

Front 44

Floating point rasters are good for

Back 44

continuous, numeric data.

Front 45

Cell Size Output options in the Raster Environments include

Back 45

max or min of inputs/ same as layer/ as specified below

Front 46

Which of the following Extent of Output options creates the output raster with an extent large enough to contain all the input rasters

Back 46

union of inputs

Front 47

When merging rasters it is important to choose the best method of handling overlap. Which of the following would be best for merging two rainfall rasters

Back 47

Mean or blend (for continuous data)

Front 48

In Raster Map Algebra the following Boolean operations will always return a Logical 0 or 1 except

Back 48

No Data

Front 49

According to your book Adjacency can be defined in a couple of different ways when you’re running a spatial selection operation. Would it be possible for Arizona and Colorado to be “adjacent” according your book?

Back 49

Based on node adjacency rather than line adjacency.

Front 50

When combining a Floating Point Raster and an Integer Raster you get

Back 50

Integer Grid

Front 51

Proximity function

Back 51

Buffer, near tool, multiple ring buffer, create thiessen polygons

Front 52

Write a Boolean Expression where all the states in the data set are selected except Texas

Back 52

NOt (State = Texas)

Front 53

Explain the following CON statement (conditional statement).

OutRas = Con(InRas1 < 5, Sin(InRas1), Con(InRas1 < 20, Cos(InRas1), Con(InRas1 > 50, 100, 0)))

Back 53

For values less than 5, the sine is calculated. For values less than 20 but greater than 5 the cosine is calculated. For values greater than 50, 100 will be assigned and all other values are assigned a value of 0 (false)

Front 54

If the value of a cell in an Input Raster is less than 20, 10 should be assigned to that cell location (true) on the output raster; otherwise, the cell values greater than or equal to 20 will be assigned 1 (false) on the output raster

Back 54

OutRas = Con(InRas < 20, 10, 1)