GEOG 4370 test 1

Input function types

Primary, Secondary, External

Analysis Functions; Non-topological types

Attribute data query, Attribute joins, Geocoding, Spatial statistics/geometry, Reclassification

Analysis functions; topological types; feature based

Spatial Query, Spatial Join, Buffering

Layer-based topological analysis

Dissolve, Overlay analysis, Network Analysis

Output types

Vector map composition, vector raster conversion

Types of topological relationships

Adjacency, containment, connectivity

Difference between geographic information systems and geographic information sciences

Systems is just the computer systems used to make maps, sciences is all the theory and practice of using the systems

fundamental ways of data representation

discrete object vs continuous field

logical model corresponding to discrete object

Vector

logical model corresponding to continuous field

Raster

Four ways to describe geographic features in GIS

Spatial data, attribute data, time, spatial relationship

Three conditions of discrete objects

Identifiable boundaries, Selective/application relevant, describable by characteristics/attributes

two primary types of coordinate systems

Plane Coordinate System, Geographic Coordinate System

Plane Coordinate System

2 Dimensional coordinate system, many options

Geographic Coordinate System

3-Dimensional Coordinate System

What are the three decisions that need to be made in a cartesian plane coordinate system

Where is the origin, What are the directions of x and y, what unit is distance

Other word for longitude and latitude, respectively

Parallels, Meridians

Transformation

Obtaining coordinates in an unknown/other coordinate system from coordinates in a known coordinate system

Steps in similarity transformation

shift, rotation, scaling

Steps in affine transformation

shift, stretch, rotation, scaling

How many reference points are needed for similarity transformation

3

How many reference points are needed for affine transformation

4

Map projection

Transformation from a 3D coordinate system to a 2D coordinate system

Four properties which can be preserved or distorted in a map projection

Area, Shape, Distance, Direction

Types of developable surfaces

Cylinder, Plane, Cone, Oval*

Developable surface

The surface which a globe is projected onto to become 2 dimensional

Standard line

The line (or lines) which the developable surface touches

Effect of standard line on distortion

No distortion at standard line, little distortion near standard line

Normal aspect

Standard line is a parallel

Transverse aspect

Standard line is a meridian

Oblique aspect

Standard line is diagonal

Mercator

A Normal aspect cylindrical projection which distorts areas close to the poles

Ellipsoid

Smooth surfaces with semiminor and semimajor radii meant to mimic the squished nature of earth

Datum

Geographic system which applies coordinates to ellipsoid as well as an origin, scale, and orientation such that the ellipsoid is a model for earth

Horizontal Datum

refers to X and Y coordinates used in a datum

Vertical Datum

Refers to Z coordinates used in a datum

UTM stands for

Universal Transverse Mercator

UTM

Transverse secant cylindrical projections repeated every 6 degrees, modified from standard mercator projection

State Plane Coordinate System

System that splits the US into 125 zones inside state lines

In a State Plane Coordinate System Vertical zones use a _____ projection

Transverse Mercator

In a state plane coordinate system horizontal zones use a ____ projection

Lambert Conformal

True or false: Vertical/horizontal zones are defined by if their state’s shape is primarily vertical or horizontal

False (California is a good example as to why this isn’t true)

How many SPCS zones are in Georgia

2

Why is topology considered geography on a rubber sheet

its relationships do not change if stretched/rescaled/rotated

topological errors in GIS

Lines intersect improperly, nodes are not created, polygons are not closed

Primary Data Input

Data collected from direct survey

Secondary Data Input

Data collected based on other sources (like a pre-existing paper map)

External Data Input

Data received directly from other sources, like preexisting data from online databases

Surveying

Collects location data on objects through angle and distance from pre-existing objects, more expensive than gps but good for very accurate mapping of small areas

GPS

Collection of satellites used to locate survey locations on earth’s surface

Table digitizing

Digitizing from a hard copy

Head’s up digitizing

Digitizing from a scanned copy

How many reference points are needed for digitizing

4

Three ways to input data for vectors

Enter data directly into the attribute table, join a table to the layer, use GIS’ computational abilities

Georeferencing

Assigning locations to geographical objects within a geographic frame of reference

Requirements for georeferenced objects

uniqueness, shared meaning, persistent through periods of time

Characteristics of georeferenced objects

Spatial resolution (how much land is referenced by each object), Domain (at what scale are the georeferenced objects relevant)

Two main types of georeferencing

Continuous georeferencing (coordinate-based), Indirect Georeferencing non coordinate-based

Example of continuous georeferencing

Digitizing

Example of indirect georeferencing

Geocoding

Examples of geocoding

Addresses, place names, intersections, zip codes, etc

Frame of reference

Background Information needed for geocoding

What frame of reference, from the census bureau, is usually used for address geocoding in the US

Tiger Road Files

How does address geocoding work

two points on either side of address are noted, address is between these two

Fuzzy address matching

AI or probability based system that allows imperfect addresses (i.e. containing misspellings) to be used

Reverse Geocoding

Getting a place name from coordinates

Linear referencing

Indirect georeferencing along a linear route based on relative distance on that route

Georeferencing with qualitative spatial relationships

Indirect Georeferencing based on more colloquial/qualitative spatial relationships (practically in GIS near or intersection)

Attribute Query

Select objects with a specific attribute (i.e. area >110 acres)

Spatial Query

Select Objects contained in a space

Attribute Join

Add one attribute table to another by shared fields (IDs)

Spatial Join

Add features FROM one join feature class TO a target feature class by topological relationship

Buffering

Adding a zone with a specified radius to a spatial feature

Topological Overlay

When features from two layers are merged in some way, resulting in a new feature

Sliver Polygon

Polygon created by imperfect overlay of two layers

How to avoid a sliver polygon

Use fuzzy tolerance, use topological editing, use a template in digitizing

How to remove a sliver polygon

Reclassify + Dissolve or eliminate

Reclassification

Merges different classifications into the same classification (i.e. reclassify all soil types into Unsuitable, Suitable, or relatively suitable)

Most common form of output

Maps

Two types of maps

Reference, thematic

Common thematic elements of a reference map

Map, Title, Legend, Source, Scale, North arrow