GIS 1 - Exam 3 (Shellito)

How do each of the following eight geoprocessing tools for polygon overlay function? (Identity, Intersect, Union, Symmetrical Difference, Clip, Erase, Update, Split)

1) Intersect: A type of GIS overlay that retains the features that are common to both layers. 2) Identify: A type of GIS overlay that retains all the features from the first layer along with the features it has in common from the second layer. 3) Symmetrical Difference: A GIS overlay that retains all of the features from both layers except for the features that they have in common. 4) Union: A GIS overlay that retains all of the features from both layers. 5) Erase: A GIS overlay that retains all of the features from the first layer except for what they have in common from the second layer. 6) Update: A GIS overlay that retains all features from the second layer as well as those features from the first layer that are not in common with the second.

What key attributes are included in a TIGER / Line file? How are these attributes used in the geocoding process?

1) The name of the street 2) The prefix of the street (North or West) 3) The suffix of the street (NW or East) 4) The type of street (Ave., Road, Blvd.) 5) The state and city of the segment 6) The zip code of the segment

What are some reasons why an address would be geocoded to an incorrect location?

1)- Misspellings, Incorrect Values, Missing information. 2)- Outdated reference database (missing Address ranges, road segments) 3) Addresses out of range 4) There's more, but I'm good.

What is a "stop" in a shortest path?

A *stop* is a destination to visit on a network.

How do buffers operate for the three vector objects?

A buffer is a zone of spatial proximity around a feature or set of features. A buffer is a feature class created by calculating a distance around an object (point, line, or polygon).

What is a TIGER / Line file? Who makes them?

A file produced by the U.S. Census Bureau that contains (among other things) the line segments that correspond with roads in the U.S.

What does the Dissolve operation do, and what is its purpose?

A geoprocessing operation that combines polygons with similar attributes together.

What does the Merge operation do, and what is its purpose?

A geoprocessing operation that combines two or more layers of data together into a single layer.

What is spatial autocorrelation? How does it help in pattern / cluster analysis?

A measure of the degree of clustering of objects & their data values.

What is the end result of a geocoding operation?

A plotted point corresponding to the address on the selected segment chosen based on the ranking system.

What is a service area? How is a service area different from a simple buffer?

A polygon boundary created around sections of a network to determine which areas of the network are within a given distance. It is different from a buffer because it is constrained by the properties of the network rather than just a large circle... For instance, a circular 1-mile buffer around a fire station is different from the places on a network that can be reached within one mile of driving along city streets.

What is the basic structure of a network in GIS (i.e. what are edges and junctions)?

A series of *junctions* and *edges* connected together for modeling concepts such as streets and routes. Junctions: nodes of a network (where edges meet) Edges: links/ line segments of a network

What is hot spot analysis? What is the result of hot spot analysis in GIS?

A technique that determines spatial clusters of high values & low values.

What is the purpose of Line In Polygon Overlay, how is it performed, and what would be the specific output of it?

A type of GIS overlay that results in a new line layer where the lines have the attributes of the polygons within which they are. An example would be overlaying roads (lines) into a county (polygon).

What is the purpose of Point In Polygon Overlay, how is it performed, and what would be the specific output of it?

A type of GIS overlay that results in a new point layer where the points have the attributes of the polygons within which they are (like overlaying well sites [points] into polygons [land parcels]).

What does the Buffer operation do, and what is its purpose?

A zone of spatial proximity around a feature or set of features.

What is transit cost?

Also called *Impedance*; It is a value that represents how many units (of time or distance) are used in moving across a network edge.

What is an Address Locator and how is it used in the geocoding process?

An ArcGIS utility that specifies the reference data, geocoding style, & necessary attributes for geocoding.

What is a spatial join?

Appending attributes from one layer to another based on the spatial relationship of the layers.

What is meant by "connectivity" in a GIS network and how and why does proper connectivity need to be set up?

Connectivity is the linkage between edges and junctions of a network. For example, if connectivity is not consistent throughout a network (two roads aren't connected in a network but they are in real-life), then you could receive misinformation from services such as Google Maps.

What is a breadth-first search (compared to a depth-first search)?

DFS (Depth First Search) and BFS (Breadth First Search) are search algorithms used for graphs and trees. When you have an ordered tree or graph, like a BST, it's quite easy to search the data structure to find the node that you want. But, when given an unordered tree or graph, the BFS and DFS search algorithms can come in handy to find what you're looking for. The decision to choose one over the other should be based on the type of data that one is dealing with. *Just remember that one picture, you know, the one from that website.

How are the results of Moran's I interpreted?

Dispersed vs. Clustered

How does Dijkstra's Pivot Point Algorithm operate? (including being able to step through the algorithm and / or diagram it, and explaining how the algorithm finds a shortest path)

Draw the picture dawg, like the one in the book. Basically... meh. **** it

What is spatial analysis?

Examining the characteristics or features of spatial data, or how features spatially relate to one another.

What are examples of different types of Address Locator Styles?

Examples: 1) Dual Ranges 2) US Address - Street Name 3) US Address - Zip 5-Digit

How is GIS used is examining patterns and clusters of geospatial data?

GIS uses spatial autocorrelation.

What is geocoding and how is it used?

Geocoding is the process of using the numbers & letters of an address to plot a point at that location. Services like Google Maps takes the address you type in & converts that info. into a location plotted onto a map.

What is "Grammar" and how is it used in the geocoding process?

Grammar basically means that during the geocoding process, different variations of words may be used when entering an address, such as: Avenue, Av., Ave...., or Road, Rd..... or North Road, N. Road, ....etc.

How does the direction (i.e which layer gets joined to which layer) used in the spatial join affect the outcome?

If you join information about the points' attributes to the polygons' attributes, you get a new *polygon* layer. If you join information about a polygons' attributes to points' attributes, you get a new *point* layer.

What are some real-world examples / applications of spatial joins using layers represented by the three vector objects?

If you want to know which county each Ohio college is in and you have a point layer showing the name and location of each university and a separate polygon layer of Ohio counties (which contain the name, pop., and spatial dimensions) you can spatially join these two layers together. The end result will be a new point layer (of colleges), where each record now has a county name and population matched to it. (pg. 188-191) for more examples.

How is Moran's I used as a statistic in measuring spatial autocorrelation?

It examines the distribution of feature locations and their values. Ex: The distance between city parking lot locations and the number of break-ins at each location.

What is the Traveling Salesman Problem (TSP), what is it an example of, and how can it be solved?

It is a mathematical process involving determining the optimal configuration of rearranging a series of stops on a network.

What is the purpose of Dijkstra's Pivot Point Algorithm?

It is a mathematical process that determines the shortest path along a network from an origin node to the other nodes on a network. ex: dawg.

What is Python and how is it used with ArcGIS?

It is an object-oriented, open source programming language used for developing scripts in ArcGIS.

What does the Getis-Ord G statistic measure in relation to patterns and clustering in GIS?

It measures High to Low clustering; "Hot-Spot analysis." It allows you to determine the degree of clustering (for high values and low values within a data set).

How is linear interpolation used to get a better spatial location match in geocoding?

Linear Interpolation is a method used in geocoding to place an address location among a range of addresses.

How are rankings used with address matching?

Rankings are used to find the best possible segment based on the address locator style and attributes. A score of 0-100 is assigned and the segment with the highest score is chosen.

How does "Selection By Location" operate as a spatial query? What is selected by a "Selection By Location" operation?

Select By Location allows you to perform spatial queries. The records/features that match the query will be selected. These features are based on spatial features and not their attributes.

What is a spatial query (and how does it differ from a regular "select by attributes" query)?

Spatial Query: Selecting records or objects from a layer based on their spatial relationships with other layers *rather than their attributes.*

What is "Address Parsing" and how is it used in the geocoding process?

The process of breaking down an address into its component parts and.... It is used....

What is location / allocation?

The process of finding the best locations for one or more facilities that will service a given set of points and then assigning those points to the facilities, taking into account factors such as the number of facilities available, their cost, and the maximum impedance from a facility to a point.

How are addresses matched to a geospatial location through geocoding?

The segments (roads) are searched according to the address locator style and the various attributes are used to find the best options for segments to match the address. ArcGIS will assign a ranking of 0 to 100 to each potential segment and the segment with the highest score is chosen.

When overlaying two polygons, what is the output of an operation in terms of the new object created and how is this new object's attribute table affected?

When 2 polygons are overlaid, the 2 layers are combined to create a new, third layer that has qualities retained from the 2 polygons used to create it. This process also combines the attributes (included in the new, third layer).

What is geoprocessing?

When an action is taken to a dataset that results in a new dataset being created.

What are some applications of Selection By Location?

You can find out how closely an object is spatially-related to another object (how far is a school from a library). Also, you can find out how many objects are within a certain area (how many Libraries are within Mahoning County).

What is a turn table and how are turns handled on a network?

a table that stores information about the cost of making each turn movement in a network. A turn table identifies the edge that the turn movement comes from, the junction where the turn occurs, and the edge that it turns onto.

What is zip code matching and why would it be used instead of address matching?

meh... I don't know damnit!

What is a line segment and how is a network modeled using line segments?

o-------------o that^ is a line segment, where: o is a junction (node) & the ----- is an edge.

What are some real-world applications of overlay operations (and how are they used)?

overlaying well sites [points] into polygons [land parcels]). overlaying roads (lines) into a county (polygon).

What is a Geoprocessing Tool (in ArcGIS)?

the tools in ArcToolbox

~What (specific) types of queries are possible with a Selection By Location operation?

~4 specific types of queries (selection by location): - Select features from - Add to the currently selected features - Remove from the currently selected features - Select from the currently selected features

~When can a spatial join be used instead of a regular join performed on two attribute tables?

~A spatial join can and should be used when two layers *do not* have a common field (attributes) between them.

For Inside, Contains, Distance, and Intersects spatial joins, how can each of them be performed as a Simple Join and also as a Summarized Join? (note that a few of these combinations cannot be performed).

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For each of the types of spatial joins, how can they be performed with each of the three types of objects? (note that a few of these combinations cannot be performed, such as polygons inside of points).

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How can you determine which layer should be joined to which layer in a spatial join (for example, if you have a schools layer and a counties layer how do you know if the counties layer should be joined to the schools layer or if the schools layer should be joined to the counties layer)?

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How does the capability of rearranging stops affect the finding of a shortest route?

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How does the maximum coverage model operate (and give some real-world examples of this)?

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How does the minimum distance model operate (and give some real-world examples of this)?

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What are some real-world applications of the "shortest path" concepts?

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What is a Simple Join? What is the result of a simple join?

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What is a Summarized Join? What is the result of a summarized join?

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What is the difference between "finding the shortest route between stops in order" and "rearranging the stops" concepts in GIS? How do these two methods find a shortest route between stops?

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What is the result of a simple distance join?

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What is the result of a summarized distance join?

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Why would linear interpolation cause an address to be matched to an incorrect location?

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