CEE 6621

2. What two options may be used to handle one-to-many relationships in a spatial join?

Summarized distance join, Summarized inside join

Coordinate System(CS)

characteristics are defined and established according to cartographic standards and enter points relative to that base.

Chapter3 summary(3)

-> UTM and state plane: common projection systems in the US ->Most coordinate system problems result from missing or incorrect labels on data sets. The Define Projection Tool is used to update a data set with an undefined or incorrect label.

Queries

-Select features of interest -explore spatial patterns -isolate features for more analysis -explore spatial relationships -create raster queries

More than one Boolean conditions

(LUCODE = 42 AND VALUE > 50000) OR SIZE > 50

&&No space in the pathnames!!

--

Chapter1 Review Questions

---

Chapter3 summary(1)

->All GIS data have coordinate systems, which define the units and axes used to represent map features as x-y coordinates. The complete definition is called the spatial reference. ->GCS, uses angular measures of lat-long with units of degrees. It is based on an approximation of the earth's shape known as a datum. ->Datum: Spheroid and its locatio relative to the earth's geoid. used to reduce errors by differenve between the spheroid and the earth's actual surface. Common: NAD 1927, NAD 1983, WGS 1984

Chapter3 summary(2)

->Data for a project should be stored in a common GCS. Transforming from one datum to another should be minimized for reduction of new errors -> map projection: mathematical equation that convert degrees from a GCS into planar coordinates. All projections introduce distortions of area, distance, direction, and shape -> Rasters have coordinate systems. Assigning coordinate systems to rasters involve creating world files for them or georeferencing them based on control points

Types of Datum

->Spheroid, oblong sphere with major and minor axis (Clarke 1886 is a common spheroid used in NA) -> Geoid, irregular, equipotential surface based on gravity. Sea level varies from place to place due to rotational, topographic, and compositional differences in the earth's mantle. World Geodetic Survey of 1984(WGS1984) ->earth centered datum that finds the best fit overall. commonly used for international data sets and web maps North American Datum of 1927(NAD1927) ->based on clarke 1866 spheroid. North American Datum of 1983(NAD 1983) -> based on more accurate GRS 1980 spheroid. ->for high precision, specialized adjustment named CORS96,HARN,NSRS2007.. Coordinate saved can differ by up to several hundred meters, cause serious registration issues for large scale maps.

Chapter1 Summary(1)

-A GIS is a database system uses both spatial&attribute data to answer questions about where things are and how they are related -> may have functions like creating data, making maps, analyzing relationships -Raster data: employ array of values representing conditions on the ground within a pixel. Array is georeferenced to a ground location(single x-y)

Chapter 10 Summary(2)

-Buffers: polygon construction, enclose the area within a certain distance. may be created for points, lines, or polygons -Append and merge: feature classes with the same feature type to be combined as a single feature class -Map overlay and spatial analysis : best done on a projected coordinate system

Chapter 4 Summary (2)

-Categorical data group objects into smaller sets identified by a unique value. Numbers may be categorical when they are used as codes. Ordinal data consist of categories that are ranked in some way. -Interval data are measured on a regular scale, and ratio data are measured on a regular scale with a meaningful zero point. -Single symbol maps and labels are used to map nominal data. Unique values maps are used for categorical or ordinal data. Interval or ratio data are displayed using graduated color, graduated symbol, proportional symbol, dot density, or chart maps.

Chapter 2 : Coordinate Systems

-Coordinate pairs: specify location and shape of a particular feature -Coordinate Space: agreed-upon range of coordinates used to portray the features

Chapter 4 Summary (1)

-Differentiating between features on a map requires variations in symbol shape, size, thickness, line type, color, pattern, or font. -Attribute data have a data type designation: nominal, categorical, ordinal, interval, or ratio. The data type determines the kind of map and even the types of analysis that may be performed on that attribute. -Nominal data name things or uniquely identify them and may be text or numbers. Each feature usually has its own value, and repeats are the exception.

Chapter 11 summary (2)

-Generally faster and better incorporates continuous data than vector overlay for suitability analysis -Boolean overlay: uses tru/false rasters and boolean operators. -distance function: can calculate costs & paths associated with traveling over a surface, additional to measuring distance -density function: number of objects occuring within a specified search radius and report it in features per unit area

Imagine a feature class of agricultural fields with attributes for the crop and the organic matter content of the soil. What issues might impact the thematic accuracy of each attribute?

-If the crops in the agriculture field face any rotation, then the recorded crop type may not match with the other crops(currently planted) on the same field -soil contains organic matter can vary with time due to decompose. Expert faces a difficult to make a boundary from one another.

Types of Geodatabases

-Personal geodatabase: stored in a single Access file -File geodatabase: can be entered by multiple operating system

Chapter 8 Summary

-Queries extract a subset of records or features from a data set based on a set of one or more conditions -Extraction functions(clip and erase) separate features of interest based on a "cookie cutter." -Attribute queries : extract features based on conditions from field in the attribute table -Spatial queries: based on criteria of how two layers are spatially related, using spatial operators to text containment, intersection, or proximity/adjacency

Chapter 11 summary (1)

-Rasters consist of spatial data stored as individual cells in an array and can represent discrete features or continuous fields of information -have coordinate systems just like other spatial data. many raster calculations are based on distance and area functions, should be in projected coordinate system with minimal distortion -map algebra treats rasters as numbers that can be added, multiplied, and otherwise manipulated on a cell by cell basis

Chapter 4 Summary (3)

-Rasters may contain thematic or image data. Discrete thematic rasters can be displayed using a unique values method. Continuous thematic rasters may be classified or stretched. Image rasters use a stretched or RGB composite display. -Continuous numeric data are classified before being mapped. Classification methods include Jenks natural breaks, equal interval, defined interval, quantile, geometric interval, standard deviation, and manual. The best classification method depends on the type of data and the data distribution. -In ArcGIS, symbols are grouped into similar themes called styles. Tools are available to allow the user to create virtually any symbol needed for a map.

2. Explain the difference between thematic rasters and image rasters.

-Thematic rasters: roads, geology of an area, elevation of an area, vegetation density of a place. include discrete rasters and continuous rasters. ->The discrete rasters : roads and land ->The continuous rasters : such as elevation. -Image rasters: aerial photography and satellite data.

Chapter1 Summary(2)

-Vector data: sequences of x-y to store discrete point, line, or pologon ->every feature is linked to an attribute table containing information about the feature -Every GIS data set has a coordinate system defined for stored x-y coordinate values. Dataset must be labeled with information about coordinate system -Map scale is the ratio of the size of objects in the map to their size on the ground. The source scale affects the accuracy and precision of GIS data and for what scales it is suitable.

drawbacks of rasters

-high precision, high storage space than vectors -one numeric attribute per rasters, vectors can store hundreds

Chapter 10 Summary(1)

-map overlay resembles a spatial join, but it splits features when they partly overlap. Enforces a one-to-one relationship between features when their attributes are joined int he output table -2 Types: union-keep all features from both layers, intersect-keep all features that are common to both input layers -dissolve: combine features if they share the same attribute. can convert many street segments into a single line feature or to remove boundaries between parcels with the same zoning

Chapter1 Summary(3)

-map scale: ratio of the size of objects in the map to their size on the ground. The source scale affects the accuracy and precision of GIS data & for what scale it is suitable.

Map Scale

-measure of the size at which features in a map are represented -when the large-scale data is needed, need more data points per unit area, increasing data storage space and slowing the drawing of layers .

Drawbacks of vector data

-poorly adapted to storing continuous surfaces(elevation or precipitation) -some types of analysis are more time-consuming to perform with vectors

Chapter 11 summary (3)

-raster interpolation: estimates a surface based on measurements at isolated locations -statistical measures can be calculated for rasters based on single cells, within a specified neighborhood -rasters can be reclassified and given new values as needed -resampling occurs automatically when rasters with different cell rasters are analyzed together but can degrade the quality of a data set. Users should attempt to minimize resampling.

The raster model

-series of small squares(cells or pixels) -each pixel contains a numeric code indicating a single attribute -stored as an array of numbers -vector can be converted to raster by selecting a single attribute to be stored in the cells -rasters store vector features in a raster format are called discrete rasters -series of rows and columns

Data quality: Generalization

-simplifying data for digital storage(turning house into a rectangular polygon) -Representation is not always "true"

Benefits of vector data

-store individual features, such as roads and parcels, with highest degree of precision -attribute table provides flexibility in the number & types of attributes that can be stored about each feature -ideal for mappmaking b/c high precision & detail of features -compact way of storing data, 1/10 space of a raster with similar information -ideal for analysis problems(determining perimeters and areas, detecting overlapping features..)

Importance of coordinate system

-when creating a vector or raster data set, one must choose a coordinate system and units for storing x-y values -have to label data so that user knows which coordinate system has been selected -Coordinate systems must match for data to be displayed together: conversion>> units defined for the map(with coordinate system, called storing units) can become map units, and may differ from stored units in the files

4. How many output fields will result if a summarized join is specified and a single statistic (e.g., Sum) is selected?

2

1. 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 in the location of the road due to the width of the line used to represent it? Give the answer in feet and miles.

3.4/72 = .047 inches of uncertainty .047/x = 1/20,000,000 x is the uncertainty

Geographic coordinate systems

3D system >> strictly speaking, cannot be displayed on a flat map or screen,. simple equirectangular projection can be applied, treats degrees as planar distances rather than as angles. Distortion are introduced latitude lines get shorter at higher latitudes on the globe but 2D its the same

3. What is the difference between a spheroid and a geoid?

A geoid is an irregular shape representing the mean sea level elevation of the earth. Spheroid is smooth with major and minor axis

1. What primary characteristic distinguishes a spatial join from an attribute join?

A spatial join combines the records of two feature tables based on the location of the feature. An attribute join combines the records based on the common field.

Thematic accuracy

Attributes some data are relatively straightforward to record(name of the city or the number of lanes in a road

Features

Basic vector objects -points: features used to represent 0d object(well, sampling locality) -> single x-y coordinate pair -lines: 1d -> endpoints(nodes) -polygons: 2d(parcel or a state) ->vertex(intermediate points), group of vertices that define a closed area

5. Why should distance joins always be performed on layers with a projected coordinate system? What kind of projection should be used?

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).

Georeferenced

Both raster and vector data are georeferenced -information is tied to a specific location on the earth's surface using x-y coordinates defined in a standard way(coordinate system)

Customizing projection with "parameters"

Central meridian: x=0 ->position near the center of the area being mapped. latitude of origin/reference latitude: y=0 ex) US has a central meridian of about 100 degrees, because the center of the continential US is there. Standard Parallels False easting/northing -> arbitrary numbers added to a coordinates in order to translate map to a new location in coordinate spae.

Coordinate systems

Choice of values and units to store a data set -Geographic coordinate system(GCS):corners are marked with degrees of latitude and longitude -Universal Transverse Mercator(UTM): markings indicate a scale in meters -State Plane: markings shows a scale in feet GPS has a flexibility of setting location in GCS degrees, UTM meters, state plane feet, or other coordinate systems

How does a clip function differ from Select By Location?

Clip can extract a portion of a feature, select by location selects a whole feature

5. What function would you use to create a map of a study area such that all the features in the map stopped at the study area boundary?

Clip tool

datum transformation

Convert from one datum to another introduce new errors in the coordinate locations.

Spatial Joins(summarized) - one to many

Counties(destination) <- Schools How many schools are in each counties? Hotel(destination) <- Attractions how many attractions are closest to each hotel?

Classes of projections

Cylindrical -> cylindrical surface that lies tangent to the earth at the equator along a great circle Transverse -> rotating the cylinder sideways and making it tangent to the earth along a line of longitude(not always prime meridian) Oblique ->tangent at an angle Tangent conic ->cone is tangent to the globe along a line of projection ->line of tangency is called standard parallel Secant conic -> cone through the sphere, it touches in two places. Azimuthal(stereographic or orthographic) ->place plane tangent or secant to the sphere ->Polar(at the poies) or oblique(not at the poles)

Labeling coordinate systems

Data sets may contain unprojected or projected data. unprojected(lat-long coordinates).

3. 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?

Discrete: store objects like roads and land ->Rainfall, temperature, slope Continuous : vary continuously, such as elevation ->soil type, voting districts, vegetation type

True or False: A shapefile of the United States with a GCS coordinate system would have an x-y extent that contains entirely positive values. ________ Explain your answer.

False :The entire xy coordinates in GCS leads to positive to negative values

The state plane coordinate system

For desired level of accuracy, most states are broken into zones with different parameters used to minimize distortion in each zones. Distortion is negligible within a single zone. Projection used ->Labmert Conformal Conic -> Transverse Mercator -> Oblique mercator The original SPCS is based on NAD27, unit in feet

Map projection

GCS is a three-dimensional coordinate system but maps need to be flat 3D to 2D is called projection

Datum

GCS location is determined when the vector defined by a latitude-longitude pair intersects the surface of the earth. Earth's shape is irregular, and its surface is only approximated different approximations developed to meet specific mapping needs (called datum)

Common projection systems

GCS: not really a projection but is treated as one UTM State Plane

CHAPTER 1

GIS Data

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?

GPS means global positioning system. Helps to locate objects with accurate latitude and longitude Two have GPS with different kinds of measurements. (in different coordinate system)

10. What is geoprocessing? In what different ways can commands be executed?

Geoprocessing applies one or more functions in sequence to solve a problem or investigate properties of data sets. By filling boxes in a window, or typing in the command line.

Longitude

Horizontal angles E or W of the Prime meridian(Greenwich)

You need to create a map for the entire state of Idaho. What options do you have? How could you get the most accurate map possible?

Idaho is split between UTM zones 11 and 12, and has three state plan zones, so one single predefined coordinate system is not available. 1) start with a utm zone and redifine the central meridian through the center of the state 2)use central state plane zone(almost be the same thing) the state is more north-south, so utm is better than a conic projection.

1. Which different types of outputs are possible (points, lines, polygons) when performing intersect and union?

Intersect: points, lines, polygons Union: polygon

Geographic coordinate system(GCS)

Lat-long system of measurement

Discrete map data

Objects with specific locations or boundaries ex) Cities, roads, soils units

6. What happens if the two input layers in a join each have a field with the same name?

One will be renamed.

6. What attribute fields will be present in a layer resulting from a dissolve?

Only one attribute field is involved

What is an operator? Describe and give examples of each of the following: arithmetic operators, logical operators, spatial operators, and Boolean operators.

Operator takes an action on or compares two entities

Attribute Queries

SELECT *FROM __TableName__ WHERE [fieldname] >= some value ex) SELECT *FROM cities WHERE [POP1990] >= 500000 SELECT *FROM counties WHERE [BEEFCOW_92] < [BEEFCOW_87]

Write a valid SQL expression to select cities between 1000 and 10,000 people using a field called POP2000.

SELECT *FROM cities WHERE [POP2000] >=1000 AND [POP2000] <= 10000

Write a valid SQL expression to select all counties whose names begin with the letter Q.

SELECT *FROM counties WHERE NAME LIKE 'Q%'

Spatial Joins(simple) - One to One or Many to one

Schools(destination) <- Counties :in which county is each school? Hotels(destination) <- Attractions :which attraction is closest to each hotel? how far is it?

2. What is the most important difference between a spatial join and a map overlay?

Spatial join cannot split features when they are partially intersect. Map overlay can

Scott is walking the boundary of a wetland area to map it. His expensive GPS records locations to the nearest 0.10 meter. Is the boundary he creates accurate? Is it precise? Explain your reasoning.

The boundary is precise but not completely accurate.

List some advantages of creating a new layer from the selected features.

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.

Union and intersect

Union combines two polygon layers, keep all areas and merging the attributes for both layers -> creates all possible polygons from the combination of features in two polygon layers Intersect merges the attributes but retains only the areas common to both layers -> two polygons layers, only keeps the areas that are shared by both inputs

Latitutde

Vertical angles above or below the equator(o) and -90 at south poile and +90 at north pole

Boolean Operators

When a query includes more than one condition, the additional operators (AND, OR, XOR, and NOT) are needed. SELECT *FROM accounts WHERE Cust = 'COM' AND Balance > 500 SELECT *FROM accounts WHERE Cust = 'COM' OR Cust = 'GOV' SELECT *FROM accounts WHERE Balance >500 AND Balance < 1500

Partial matches in text

When using LIKE, a wild card character (% for shapefiles, * for gdb) is used ex) selecting cities based on their NAME field NAME LIKE 'NEW &' (shapefile) NAME LIKE 'NEW *' -this doesn't include Newcastle because there is no space in the letter NAME LIKE '%Smith%' customers with name Smith

Continuous map data

a quantity that is measured and recorded everywhere over a surface ex) temperature, elevation

2. What are the x-y coordinates of a map's origin? ___________ What is the x coordinate along the central meridian?______________________

a. 0,0 b. 0

You measure a football field (l00 yards long) on a large-scale map and find that it is 0.5 inch long. What is the scale of the map?

a. 1:7200

2. 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?

a. 3 feature classes (states, cities, and rivers) b. 650 features (50+500+100) c. 3 attribute tables, one for each feature classes d. 650 total records

6. What is the difference between a central meridian and the Prime Meridian?

a. Central meridian is the tangent of a projection, prime meridian is in Greenwhich, England.

explain why conic projections usually conserve area and distance but cylindrical projections typically preserve direction.

a. Cylindrical projections are more distorted away from their tangent b. Conic conforms more closely to the surface Conic projections have decreasing lengths of the parallels as you approach the poles, which mimics the decrease in the circumference of the earth towards the poles.

1. Explain the difference among the terms feature, feature class, and feature dataset

a. Feature represent the items and characteristics in the space, represented with line, point, polygons. You may call features as spatial objects. b. Feature class is the collection of common features that have same spatial/geometric representation. An example of the feature class is the line representing road centerlines. c. Feature dataset is a collection of related feature classes that share a common coordinate system. It is used to spatially or thematically integrate related feature classes. It serves the purpose to organize related feature classes for building a topology or utility system.

1. If a data set's features have x coordinates between -180 and +180, what is the coordinate system likely to be? In what units are the coordinates?

a. GCS, geographic coordinate system b. In longitude degrees

5. What extra step is performed when projecting rasters that is not needed when projecting vector data? What happens during this step?

a. Specify a new cell size b. Cell center recalculated and resampled, resampling occurs

Would raster or vector be a better format for storing land ownership parcels?

a. Vector is a better format for storing land ownership parcels. b. Reason 1: Raster stores data in individual pixels. Showing the outline of a single parcel with vector is better to make sorting with the information about the parcel. c. Reason 2: Vector data need less space to store and run a software. d. Reason 3: Vector data can calculate proximity data easily than the raster data.

7. You have a shapefile with an Unknown coordinate system, but a file on the web site says that the coordinate system is UTM Zone 13 NAD 1983. What is your next step?

a. match the coordinate system by using toolbox-define projection

In the map

always have scale, direction, legend, ..

Append and Merge

append: combine features of two or more layers and place them into an existing target feature class -> required to be the same features(both polygons, both lines, both points Merge : it creates a new feature class, offeres more flexible treatment of attribute tables -> instead of institing that two tables match, it allows user to specify the fields to be included in the output feature class and which table they will come from.

Universal Transverse Mercator(UTM) system

based on secant transverse cylindrical projection 1 zone is 3degrees each side of the central meridian between latitude lines. projection is true along the lines of tangency, the distortion inside the zone is minimal to map different intervals, cylinder is rotated about the globe in 6 degree intervals, 60 zones around the world each UTM zone has own central meridian, splits at the equator into a north ands south component To eliminate negative x-y coordinates, southern zones have a false northing of 10 million meters(equator is zero) and both northern and southern zones has a false easting of 500,000 meters

Extraction functions

clip and eratse clip : cookie cutter, truncate the features of one file based on the outline of another Erase: keep features that fall outside the erase layer.

Map overlay

combines two layers to create a new output feature class containing information from both of the inputs.

Feature Dataset

contain multiple feature classes that are related to each other ex)transportation: roads, traffic lights, railroads, airports, canals

Shape files

contains A feature class composed of points, lines, polygons never a mixture

Buffer

delineate areas that fall within a certain distance of a set of features

Drawbacks of projection

distortion: area, distance, shape, direction

continuous raster

elevation

feature class

features are grouped into data sets -roads and rivers are different types of features, would be stored in separate feature classes -one kind of geometry-- point, line, polygon but never a combination -informationstored in attribute table -FID or OID links the spatial data with the attributes

8. How can you determine the areas of polygons in a geodatabase? In a shapefile?

gdb: already have a feature class that is SHAPE_AREA Shape file:

Dissolve

groups features together based on whether they share the same value of an attribute field. output may be single feature or multi features. unconnected areas constitute a single features.

Proximity

how close features in A are to features in B -are within a distance of adjacency is different, where the distance goes to zero -share a line segment with and touch the boundary of operators

Geometric Accuracy

how close x-y values of data set correspond to actual locations on the earth's surface

attribute data

information being represented ex) soil type, chemical analysis of a well

3. 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 layer be?

lines

Cardinality of relationship: many to many

many record in the destination tables matches many record in the source table, student may take more than one class, most classes have more than one student

Cardinality of relationship: many to one

many record in the destination tables matches one record in the source table, many cities in one state

Thematic mapping

map that are colored/marked based on an attribute field

Benefit of rastsers

mitigate the drawback of vectors -ideal for storing continuous information; each cell value completely different from its neighbors -simple&rapid analysis -extensive set of analysis tools for rasters

Geodatabase

mixture of feature classes, networks, tables, rasters,.. -feature classes may exist as individual objects in a geodatabase or it could be a feature dataset(folder for organizing objects)

vacancy rate

normalize by # of houses

Cardinality of relationship: one to many

one record in the destination tables matches more than one record in the source table The rule of joining is violated. perform relate

Cardinality of relationship: one to one

one record in the destination tables matches one record in the source table

7. Why is it usually advantageous to use a projected coordinate system when doing a map overlay?

projected coordinate systems use distance and area, while geographic coordinate systems use shape and direction

Intersection

returns any feature in A that touches, crosses, or overlaps any part of a feature in B

discrete raster

roads, land use polygons..

x and y coordinates

spatial data

Overlay with attributes

spatial joins fail when spatial features do not overlap exactly. Ex) map of roads and land use state gov request a report of the total miles of the road falling into each land use category. Spatial join does not work because road does not lie entirely inside a polygon

raster model

store continuous data -spatial and attribute data

Vector Model

store discrete data -spatial and attribute data

9. What determines the coordinate system of the output when overlay is used?

the feature dataset

Coordinate system and projection: Terminology

they are used interchangeably to refer spatial reference. Coordinate system: only part of the spatial reference projection: mathematical conversion from 3D to 2D coordinate system

You have a shapefile with a UTM Zone 10 NAD 1983 coordinate system, and you want to bring it into your state database, which uses the Oregon Statewide Lambert coordinate system. What is your next step?

use project tool to convert the shape file to a new shape file with the oregon statewide coordinate system

Spatial queries

use spatial operators - containment, intersection, proximity

3. What are slivers? Explain how they can be prevented.

very small polygon or line that results from overlay of two close but not exact boundaries. Prevented through specifying tolerance

Contain

whether one feature includes another A completely contains B returns features in A that fully surround the features in B A contains B : B is inside A but they share a boundary are within and are completely within is inverse of contain

resolution

x-y dimension of each pixel higher the resolution, more precise the data represented

4. What is a buffer? Why is a dissolve often performed when buffering features?

zone around a map feature measured in units of distance. dissolve is performed to get rid of the boundaries between them. Also removes the overlapping areas to create a single region.