# Midterm

A feature is a spatial object composed of one or more x-y coordinate pairs and having one or more attributes in a single record of an associated table. A feature class is a set of similar objects with the same attributes stored together in a spatial data file. A feature dataset is a set of feature classes in a geodatabase that share a common coordinate system and can participate in networks and topology
Explain the difference among the terms feature, feature class, and feature dataset.
3 feature classes. 650 features. 3 attribute tables. 650 records.
Imagine you are looking at a geodatabase that contains 50 states, 500 cities, and 100 rivers. How many feature classes are there? How many features? How many attribute tables? How many total records in all the attribute tables?
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Rainfall: continuous. Soil type: discrete. Voting districts: discrete. Temperature: continuous. Slope: continuous. Vegetation type: discrete.
If the following data were stored as rasters, which ones would be discrete and which would be continuous: rainfall, soil type, voting districts, temperature, slope, and vegetation type.
John’s GPS is in meters and Mary’s is in feet. To make the units agree, they need to be set to the same coordinate system.
John and Mary are collecting GPS data together. John’s GPS says their location is at (631058, 4885805). Mary’s GPS says their location is at (1204817, 663391). Explain what is going on. What must be done to make the GPS units agree?
Vector data would be better. Not very much detail is needed besides the outline of the parcels, so vector is a simpler way of storing it, plus it can also give information about the parcels in the attribute table. It would also take up much less space. Finally, calculating things like area and proximity of one parcel to another is easier with vector data.
Would raster or vector be a better format for storing land ownership parcels? Give at least 3 reasons for your choice.
1:200
You measure a football field (100 yards long) on a large-scale map and find that it is .5 inches long. What is the scale of the map?
The boundary will be fairly precise, though it may not be completely accurate, especially if the area has a tortuous boundary that may not be accounted for as he walks around it.
Scott is walking the boundary of a wetland area to map it. His expensive GPS records locations to the nearest .10 meter. Is the boundary he creates accurate? Is it precise? Explain your reasoning.
If the crops are on a rotation, the crop type that is recorded may n0t match up with the one that is currently planted on the field. Organic matter of the soil may also vary with time, and it is also difficult to draw a distinct boundary across things like soil types, which may gradually change from one to another.
Imagine a feature class of agricultural fields with attributes for the crop and the organic matter of the soil. What issues might impact the thematic accuracy of each attribute?
GIS services can store many types of information, from vector and raster data to geodatabases, which can be manipulated. Information from Internet-based data services can also be used.
Explain some ways that GIS services are different from the data that reside on your hard drive.
Mastering ArcGIS (2014) [textbook]. McGraw Hill, contact information. Resource URL: [June 2015].
Construct an appropriate citation for the data that come with this book.
Find this out…
A 1:20,000,000 scale map of the United States displays the interstates with a line symbol that is 3.4 points wide. There are 72 points to an inch. What is the uncertainty of the location of the road due to the width of the line used to represent it? Give the answer in feet and miles.
Bushels of wheat per county: ratio. Vegetation type: categorical. Average maximum daily temperature: interval. Parcel street address: nominal. Parcel ID number: nominal. pH measurement of a stream: interval. State rank for average wage: ordinal. Number of voters in a district: ratio. Student grade in a class: ordinal. Soil type: categorical.
For each of the following types of data, state whether it is nominal, categorical, ordinal, interval, or ratio: bushels of wheat per county, vegetation type, average maximum daily temperature, parcel street address, parcel ID number, pH measurement of a stream, state rank for average wage, number of voters in a district, student grade in a class, soil type.
Precipitation: graduated color. Geological unit: unique values. Acres of corn planted per county: graduated color. Rivers: single symbol. Land use: unique values. Household income: graduated color.
For each of the following attributes, state whether a single symbol, graduated color, or unique values map would be most appropriate: precipitation, geological unit, acres of corn planted per county, rivers, land use, household income.
Average daily temperature: no. Number of Hispanics: yes. Square miles of parkland: yes. Median rent: no. Total river miles: yes. Sales tax rate: no.
If mapping the following attributes for counties, indicate which ones would generally be normalized and which would not: average daily temperature, number of Hispanics, square miles of parkland, median rent, total river miles, sales tax rate.
Geological units: unique values. 4-band satellite image: RGB composite. Landslide hazard (high, medium, low): classified. Black-and-white aerial photo: stretched. Precipitation: classified. Slope in degrees: stretched.
State whether you would use a unique values, classified, stretched, or RGB composite display method for each of the following rasters: geological units, 4-band satellite image, landslide hazard (high, medium, low), black-and-white aerial photo, precipitation, slope in degrees.
Counties
Which would take more storage space, a layer file showing all of the US counties or a layer file showing all of the US states?
The colleague does not have access to the same data in the same disk location as Jill.
The data to which the document was linked is no longer accessible once the link has been broken.
Jill creates a map document and emails it to a colleague in another state. He calls and tells her the documents open, but no map appears. Explain what is wrong.
Jill creates a map document using data from a central filesaver and emails it to a colleague in her office. Again, no map appears. What is wrong this time?
Spaces and special characters (such as #, @, &, *, etc.).
What characters should be avoided when naming GIS folders, files, and map documents?
Thematic rasters represent map features or quantities (e.g. roads, geology, elevation, vegetation density). Thematic rasters are grouped into discrete rasters (when rasters are used to store objects, such as roads or land use polygons) and continuous rasters (values represent a continuously varying quantity, such as elevation).
Image rasters include aerial photography and satellite data. The pixels represent degrees of brightness caused by lightness reflecting from materials on the surface. May contain one or more bands of information.
Explain the difference between thematic rasters and image rasters.
A red exclamation point indicates that the pathname link (the links to the data) is broken. This can be fixed by manually locating the data.
What does it mean if you find a red exclamation point next to a map layer? How would you fix it?
– What is the message of the map?
– Who is the map’s audience?
– How will the map be used?
– Are there possible privacy issues with the map’s information?
List 4 questions about map objectives that would influence the design of a map.
Balance means that the elements are evenly arranged on the page and are a good size relative to each other. This means that objects should not crowd each other, large areas of blank space should be avoided, etc.
What factors should be considered in evaluating the balance of a map?
Earth tones generally work best. Psychology of colors can be used in representing objects in an easily identifiable manner, such as by making water blue and land green. It can also be used to emphasize danger by using red, for example.
What types of colors generally work best for maps? How can the psychology of colors be used to enhance a map’s meaning?
– Using too many significant figures (e.g. 124932 vs. 125000)
– Not renaming the file if it shows up as the heading cities.shp as opposed to just US Cities)
– Using an outline that crowds the text within the legend
List 3 common pitfalls that amateurs make when creating legends.
A geographic coordinate system is one that is based on latitude and longitude and is measures in degrees. Because it treats coordinates as if they are on a plane, rather than sphere, it causes distortion and elongates features in the east-west direction.
What is a geographic coordinate system, and why is it a poor choice for creating maps?
Area, distance, shape, direction. Conic projections preserve area and distance. UTM is cylindrical, so it distorts distance and area, while preserving direction and shape. State plane aims to preserve all 4 properties, but only for the small area on which it focuses.
What 4 properties are distorted by map projections? Which tend to be preserved by conic projections? What distortions are present in UTM and State Plane projections?
A map of a country: Albers Equal Area Conic. A map of the United States: Albers Equal Area Conic. A United States map used to calculate distances: Equidistant Conic. A United States map used to calculate areas: Lambert Azimuthal Equal Area.
List which projections might be suitable for a map of a country, a map of the United States, a United States map used to calculate distances, and a United States map used to calculate areas.
A north arrow will not point up when a projection that distorts direction is used. In this case, a north arrow should not be used.
When does a north arrow not point up? When should a north arrow not be used?
As a feature class in a database.
If you have an ArcGIS Basic license and wish to create and use annotation in different map documents, how would you need to store it?
Map scale is the ratio of feature size on a map to its size on the ground. Scale range is the range of scales for which a data layer will be displayed. The reference scale is the scale at which text or symbols appear at their assigned size.
What are the differences among the map scale, the scale range, and the reference scale?
An attribute table contains information about features in a geographic data set. There is always one row of information for each feature.
A standalone table simply contains information about one or more objects in tabular format instead of having information about map features.
Describe the difference between an attribute table and a standalone table.
Relational (RDBMS). In this system, the user can create relationships between tables.
Which type of database management system are GIS systems based on? How does this type of system differ from other DBMS types?
Lots of tabular data sources, including dBase files, INFO files, geodatabases, SQL queries, or comma-delimited files.
List the types of data source from which tables may display data.
In ASCII each number, letter, and symbol is assigned a single-byte code between 0 and 255, so the number 255 would require 3 bytes of data. Binary stores the number in base 2, rather than being assigned one byte per character, so 255 will be 8 bytes of data.
Describe how storing the number 255 in ASCII differs from storing it as a binary representation.
Populations of countries in the world: long. Precipitation in inches: float. Number of counties in a states: short. Highway name: text. Distances between US cities (in meters): long. Birthdays: date.
Choose the best field type for each of the following types in a geodatabase: populations of countries in the world, precipitation in inches, number of counties in a states, highway name, distances between US cities (in meters), birthdays.
Students to college classes: many-to-many. States to governors: one-to-one. Students to grades: one-to-many. Counties to states: many-to-one.
What is the cardinality of each of the following relationships: students to college classes, states to governors, students to grades, counties to states.
In a join, tables are combined using a common field (a key). The two separate tables become one and contain the information from both tables. This temporary relationship can be removed when it is no longer needed.
In a relate, two tables are still associated by a common field, but the records are not joined together and the two tables remain separate. However, if one ore more records is selected in one table, then the associated records can be selected in the other table.
Describe the differences between a join and a relate.
Cardinality is one state to many airports (or the inverse). Can be joined if states is the source and airports is the destination, but not the other way around.
You have a table of states and airports, both with a state abbreviation field. Can you join them if states is the destination table? If airports is the destination table? Explain.
The Summarize function will combine the records into groups based on a categorical attribute field and then calculate statistics separately for each group. On the other hand, Statistics will only show data for the group as a whole.
Describe the difference between using Statistics and using Summarize functions on a field.
Find all towns with more than 20,000 people: query.
Find the total number of volcanoes in each state: summarize.
Determine the total damage caused by earthquakes in the United States: statistics.
Find the states in which Hispanics exceed the number of African Americans: query.
Find out which subregion of the country has the most Hispanics: summarize.
For each of the following problems, using data sets for the United States, state whether using a query, the Statistics function, or the Summarize function would be the best approach to solving it:
Find all towns with more than 20,000 people.
Find the total number of volcanoes in each state.
Determine the total damage caused by earthquakes in the United States.
Find the states in which Hispanics exceed the number of African Americans.
Find out which subregion of the country has the most Hispanics.
A query is an operation to extract records from a database according to a specified set of criteria.
What is a query?
[POP2000]>1000 AND [POP2000]<10000
Write a valid SQL expression to select cities between 1000 and 10,000 people using a field called POP2000.
[NAME] LIKE ‘Q%’
Write a valid SQL expression to select all counties whose names begin with letter Q.
Students in New Jersey: 500
Students with GPA greater than 3.0: 600
Let T be a table containing all students attending a community college in New York. Let A be the subset of students living in New Jersey. Let B be the subset of students with a GPA greater than 3.0. The query A AND B yields 200 records. The query A OR B yields 1100 records. The query A NOT B yields 400 records. Construct a Venn diagram for the sets, labeling each section with the number of students. How many students live in New Jersey? How many students have a GPA greater than 3.0?
No, because it is impossible to determine how many student live outside of New Jersey and do not have at least a 3.0 GPA.
Let T be a table containing all students attending a community college in New York. Let A be the subset of students living in New Jersey. Let B be the subset of students with a GPA greater than 3.0. The query A AND B yields 200 records. The query A OR B yields 1100 records. The query A NOT B yields 400 records. From this information, can you determine the number of students attending the community college? If yes, state how many. If no, explain why.
Selectable layers controls which layers can be selected and from which information can be selected. The default setting is that all layers are selectable.
What does it mean selectable layers? What is the default setting?
Yellow and orange candies and cashews.
Imagine that you have some trail mix composed of peanuts, raisins, almonds, cashews, dried cranberries, and chocolate candies colored red, green, yellow, and orange. Imagine that you apply the following set of “queries” to the trail mix:
Create new selection all candies
Add to selection cashews
Remove from selection red and green candies
Select from selection all nuts and candies
What do you have selected now?
[ZONE] = ‘COM’ AND [ZONE] = ‘RES’
Should be OR because none of the zones will be both.
[COVTYPE] = ‘SPRUCE’ AND [CROWNCOV]>50
Correct
[POP2000]>2000 OR [POP2000]<9000 Should be AND because OR will cause all values to be selected. [INCOME]<100000 AND [INCOME]>50000
Correct
For each of the following queries, state whether the syntax is correct or incorrect. If incorrect, explain why.
[ZONE] = ‘COM’ AND [ZONE] = ‘RES’
[COVTYPE] = ‘SPRUCE’ AND [CROWNCOV]>50
[POP2000]>2000 OR [POP2000]<9000 [INCOME]<100000 AND [INCOME]>50000
An operator is a term used in queries to specify what is sought in the expression.
Arithmetic operator: +, -, *, /
Logical operators: <, >, =, <>
Spatial operators: containment, proximity, intersection
Boolean operators: AND, OR, XOR, NOT
What is an operator? Describe and give examples of each of the following: arithmetic operators, logical operators, spatial operators, and Boolean operators.
The layer can be given its own symbols and be displayed separately from the original layer. Preserves the selected features for future reference and eliminates the risk of accidentally clearing the selection. Can also be saved as a layer for use in other documents.
List some advantages of creating a new layer from the selected features.
A spatial join uses the locations of the features to decide which rows in a table match (as opposed to using a common field in an attribute join).
What primary characteristic distinguishes a spatial join from an attribute join?
Summarized inside or summarized distance joins.
What 2 options may be used to handle one-to-many relationships in a spatial join?
Lines.
If a polygon feature type is joined to a line layer, with the lines as the destination table, what will the feature type of the output table be?
One.
How many output fields will result if a summarized join is specified and a single statistic (e.g. sum) is selected?
Because a geographic coordinate system uses units of decimal degrees, which cannot easily be converted into miles or kilometers, plus the result could be invalid because the geographic coordinate system uses spherical coordinates. In this case, it would be best to use a conic or azimuthal projection (e.g. UTM, State Plane, Equidistant Conic).
Why should distance joins always be performed on layers with a projected coordinate system? What kind of projection should be used?
One will be renamed.
What happens if the 2 input layers in a join each have a field with the same name?
1. Table of watersheds with the number of parcels in each.
2. Watersheds.
3. Inside.
4. One-to-many.
5. Summarized.
6. Summarized inside.
Determine the number of parcels within each of Austin’s watersheds.
1. What should the final output layer/table look like?
2. Which is the destination layer?
3. Should a distance join or an inside join be used?
4. What is the cardinality of the join?
5. Should a simple join or a summarized join be used?
6. Which join type is this? Simple inside, simple distance, summarized inside, or summarized distance.
1. Table of houses with the closest school for each.
2. Houses.
3. Distance.
4. Many-to-one.
5. Simple.
6. Simple distance.
Find the closest school for each house in a realtor’s database.
1. What should the final output layer/table look like?
2. Which is the destination layer?
3. Should a distance join or an inside join be used?
4. What is the cardinality of the join?
5. Should a simple join or a summarized join be used?
6. Which join type is this? Simple inside, simple distance, summarized inside, or summarized distance.
1. Table of wells with the zoning type for each.
2. Wells.
3. Inside.
4. Many-to-one.
5. Simple.
6. Simple inside.
Find the land use zoning type associated with each well in Atlanta.
1. What should the final output layer/table look like?
2. Which is the destination layer?
3. Should a distance join or an inside join be used?
4. What is the cardinality of the join?
5. Should a simple join or a summarized join be used?
6. Which join type is this? Simple inside, simple distance, summarized inside, or summarized distance.
1. Table of airports with the sum of people and counties.
2. Airports.
3. Distance.
4. One-to-many.
5. Summarized.
6. Summarized distance.
Determine the number of counties and the total number of people served by each airport in the United States.
1. What should the final output layer/table look like?
2. Which is the destination layer?
3. Should a distance join or an inside join be used?
4. What is the cardinality of the join?
5. Should a simple join or a summarized join be used?
6. Which join type is this? Simple inside, simple distance, summarized inside, or summarized distance.

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