Study Guide for Quiz 2 (Lectures 7-10) PDF

Study Guides for Quiz 2 (Lectures 7-10) NOTE: Some knowledge points require the previous pages as important contexts to understand them. Please do NOT only read the marked pages. Lecture 7: What are the major types of projections based on projection surface? (p9) Cylindrical, conic, and a...

Study Guides for Quiz 2 (Lectures 7-10) NOTE: Some knowledge points require the previous pages as important contexts to understand them. Please do NOT only read the marked pages. Lecture 7: What are the major types of projections based on projection surface? (p9) Cylindrical, conic, and aziumuthal What are equatorial/normal, transverse, and oblique cylindrical projections (p13)? Equatorial/normal - uses cylindrical surface that lays tangent to the earth at the equator Transverse - rotates the cylinder sideways and makes it tangent to the earth along a line of longitude Olique - places the tangent at an angle (skew axis) What are tangent and secant cylindrical projections (p14)? Tangent - if the cylinder is tangent to the globe along a line; has ONE standard parallel Secant - if the cylinder is placed through the globe (sphere) so that it touches two places; has TWO parallels  What are tangent and secant conic projections (p15)? Same as cylindrical but the setting is a cone (point of cone aligns with one of the poles) What is azimuthal projection (p16)? Based on setting a PLANE tangent or secant to the sphere - If center of plane is on one of the poles = POLAR AZIMUTHAL - If plane is at an angle = OBLIQUE azimuthal What are the basic parameters of a projection (p17)? - Standard parallels - Central meridian (x=0, meridian close to the center of the map) - Latitude of origin (y=0, equator) - False easting (used to ensure x coordinates are all +) - False northing (used to ensure y coordinates are all +)  Summary of projection summary (p19) - Three types of projections: normal/equatorial, transverse, oblique - Three types of projectections based on projection surface shapes: azimuthal, cylindrical, and conic - Conformal = A projection that preserves the local shape of features across the map - Equal area/equivalent = a projection that preserves the area of a feature across the map What are the characteristics of Mercator projection and what is the appropriate application of this projection (p23-24)? - Cylindrical projection (north and south = up and down) - Conformal (preserves shapes) - Distorts area (areas closer to the equator are accurate, but not near the poles) - Produces straight meridians and parallels, perpendicular, producing grids - Appropriate for large - scale mapping of the areas near the equator - Upper and lower limits of latitude are 89° N and 89° S How is Web Mercator different from Mercator projection and what is the appropriate application of Web Mercator projection (p25)? - Uses spherical model instead of elliposodial - Used by online mapping (google maps) - Has area and distance distortions - ESPG 3857 What are the characteristics of Lambert Conformal Conic projection and what is the appropriate application of this projection (p26-27)? - Based on 2 standard parallels - Best suited for conformal mapping of land masses from east to west - Meridians converge at poles - Albers is the same but preserves area rather than shape - Both poles are represented as arcs  How does the Universal Transverse Mercator work (p30), and what is the appropriate application of this projection? (p32)? - Divides earth into zones that are 6° wide in longitude - Extends from 84° N latitude to 80° S latitude - Zones are split north or south of the equator - No distortion along central meridian - Ideal for local, country, or small state maps What are the characteristics of State Plane Coordinate System and what is the appropriate application of this projection (p35-36)? - N to S zones used Transverse Mercator - E to W zones use Lambert Conformal Conic - Alaska uses Oblique Mercator - Used for cadastral mapping and engineering - Some smaller states use a single state plane zone - Larger states are divided into several zones What is a projection file and what is it used for (p43)? - The behind the scenes, defining a projection simply by creating text file that describes the Spatial Reference of the data - Used for - Transforming geographic coordinates to cartesian coordinates - Transforming one projected coordinate system to another Lecture 8 What is a table and what are the types of tables (p6-7)? - A data structure to store attributes - Standalone tables: store tabular data from any source (independent of geographic dataset) - Attribute tables: store data associated with a spatial feature class What is record, field, and attribute in an attribute table (p9)? - Record = rows - Fields = columns - Attribute = non-spatial characteristics associated with spatial data, (population of counties) What is a shapefile (p11) and what are file formats to compose a shapefile (p13)? - A collection of geographic features that share the same geometry type  (point, line, polygon) and the same attribute fields for a common area (consists of spatial coordinates and associated attributes) -.shp - main file; required -.shx - index file; required -.dbf - dBASE table; required What is the concept and principle of editing vector data (p15)? - Editing = updating existing feature classes or creating new ones - Principle = to create and maintain topological integrity between features What is class overlay (p22)? - Combining spatial and attribute data from 2+ spatial data layers - Combines different thematic data layers to extract new info (data layers should be in the same coordinate system) What is intersect and union(p25-26) and how are they different in their applications (p28)? - Intersect = overlay that combines data from both layers, but only for the area where both layers overlap/ contain data - Union = overlay that includes all data (also attribute data) from both the counting and input layer (no geographic and attribute data is discarded) Lecture 9 What is buffer and what are the types of buffers (p8-10)? - A region that is less than or equal to a specified distance from 1+ features - Point layer - Simple buffer, overlap dissolved - Compound buffer, overlap identified - Nested buffer What is variable distance buffer and how is it applied (p11)? - A buffer where each feature is assigned a different buffer distance - Ex: a buffer distance for intensive cultivation is probably larger than for organic farming - Using a field within your attribute table that has different buffer distances  for each individual feature What is clip and difference (p12-14)? - Clip = extract area of interest from features; used to define the areas for which features and attributes will be output (cookie cutter) - Difference = input layer features that partially overlap the overlay features and only the portions OUTSIDE the overlay layer features are retained What is dissolve (p15) and merge (p17)? - Dissolve = removes boundaries of features with the same value in the specified attribute field - Merge = combines all features from 2+ data sets into a single new feature class; combines adjacent feature classes (same fields) What is spatial data analysis and what are the outputs of spatial data analysis (p19-20) - Application of operations to spatial and attribute data to solve a problem - Output is either spatial (new layer) or nonspatial (scalar value, list, table) What is query and what are simple and compound queries (p23)? - Query = selection of a subset of records based on the values of specified attributes (census blocks with a size great than 1 sq mi, parcels for which taxes haven’t been paid) - Simple query = one variable - Compound query = using conditions and/or multiple variables What are the basic Boolean operators and what are their characteristics (p24)? - AND combinations = decrease number of records (restrictive) - OR combinations = increase or add number of records to a selected set (INCLUSIVE) - NOT combinations = records that do not meet the conditions What is spatial selection (p27) and what are the types of spatial relations (p28- 29)? - Spatial selection = based on spatial relationships to other geographic  features; unique to spatial data and not possible for tabulated data - Spatial relation types - Intersect = fully or partially within or touch - Are within = fully within - Contain = opposite of area within - Disjoint = no overlap or touching - Equal = tests if geometries are the same - Touch = touching only - Overlap = partially overlapped What are the common methods of classification (p30)? - Binary classification (0 and 1, true and false) - Equal - interval (highest-lowest) - Natural breaks (obvious breaks or gaps in the data) - Quantile (groups data into classes with an equal number of features/values - Equal area (equal proportion of study area per class) - Standard deviation (shows how much a feature’s attrbute value varies from the mean) What are some principles to use expression in field calculator (p40)? - Operators should be placed without any special formatting - Fields should be surrounded by “quotes” (“State Name”) - Text values should be surounded by ‘single quotes’ (‘Washington’) - Whole numbers (integer) decimal numbers (float) should be entered without any surrounding characters Lecture 10 What are the data sources, geographies of U.S. census data? How to choose between geography (p5) - TIGER (Topologically Integrated Geographic Enconding and Referencing data) - Levels of nested geography: country, region, division, state, county, census tract, block group, census block - Lowest levels contain more detuaked info but lack full coverage - Census tract scale gas complete geographic coverage What is the smallest geography in ACS 5-year data and what are included in  ACS 5-year data (p10-11)? - Smallest geography = block group - Dont have to meet a particular population threshold in order to be published - Detail tables, subject tables, data profiles, and comparison profiles What are the characteristics of decennial census data (p14-15)? - Population data by sex, race, age, Hispanic origin - Housing data by occupancy, vacancy staus, and tenure - Highest geographic resolution (changes every 10 years) What are the characteristics of census tracts, block groups, and blocks (p17)? - Census tracts = small, permanent, consistent statistical divisions of a county; optimally contains 4,000 people - Block groups = smallest units for tabulation of sample data, population ranges from 600 to 3,000 - Blocks = smallest units of data tabulation, cover entire nation, nest within all other types of geographic areas, avg 100 people How is a GEOID composed of (p21)? - Numeric codes that uniquely identify all administrative/legal and statistical geographic areas for which the Census Bureau tabulates data What is a density map and how is it applied (p34) - A visual representation that displays the distribution and intensity of a variable across a geographic area - Uses color gradients or contour lines to indicate areas of higher or lower density What are search radius and cell size of heat maps and what is the tradeoff to select different values of search radius and cell size (p36-37) - Search radius = area around each cell the GIS software will factor into the density calculation - Too small - patterns restricted to immediate area - Too big - patterns will become too generalized - Cell size = determining factor as to the degree of detail in terms of  coarseness of the resulting density surface - Too large - more staircase effect on resulting surface layer - Too small - smoother surface but processing will take longer and will result in larger file size