GIS Midterm Review

Advantages of proportional symbol map

Can be useful to show multiple variables if used in graph format

Principles of Map Design

1) Purpose 2) Geographic space/expanse 3) available data 4) map scale 5) audience 6) conditions of use 7) technical limits 8) conventions and standards

Data Classification order

1. Equal intervals 2. Quantiles 3. Natural Breaks/optimal (jenks) 4. Mean/standard deviation 5. Manual 6. Geometric interval

Data are organized into 4 different levels

1. Nominal (Categorization) 2. Ordinal (Categorization & Ordering) 3. Interval (Ordering & Explicit Values, arbitrary zero) 4. `Ratio (Ordering & Explicit Values, non-arbitrary zero)

Map projection steps

1. Reduce the Earth's size to that of an imaginary globe 2. Project the graticule from the reference globe onto the developable surface

Spatial queries

A GIS lets you select spatial features based on their location relative to other spatial features. uses "select by location" tool

What is GIS?

A computerized system for capturing, storing, analyzing, visualizing & managing data, data which are spatially referenced.

Coordinate system

A coordinate system is a reference system used to represent the locations of geographic features, imagery, and observations such as GPS locations within a common geographic framework.

Datum

A datum defines the position of the spheroid/ellipsoid relative to the center of the earth. (ie It defines the origin and orientation of latitude and longitude lines.)

Mollweide Projection

An equal-area map which shows the correct size of landmasses in relation to other landmasses but distorts shape - ellipse

Disputed borders

Approximately 75% of the territories around the world have some form of territorial dispute e.g. China has 17 territorial disputes with its neighbours, on land & sea

Polygon example

Area features: Countries, states, oceans

Types of queries

Aspatial and Spatial

First maps

Babylon (600BC) Ptolemy's Map (150AD)

Can you name the early American public land surveyor and cartographer who drafted this map of a portion of the Ohio River in Pennsylvania in 1752?

George Washington

Line example

Linear features: roads, rivers, rails, etc

Disadvantages of proportional symbol map

Can become crowded on maps with small enumeration units

4 thematic mapping techniques

Choropleth Proportional Symbol Isarithmic Dot Mapping

Map projection characteristics

Class, Case, Aspect

Natural Breaks (Jenks)

Classes are based on natural groupings inherent in the data through examination of the histogram

Advantages of quantiles

Easy (manual) Calculation Allows use of the complete color spectrum

Advantages of equal intervals

Easy Calculation Easy Interpretation No Gaps

Three types of Coordinate Systems

Geographic coordinate systems Projected coordinate systems Grid Systems

Three types of coordinate systems

Geographic coordinate systems, Projected coordinate systems, Grid Systems

Projected Coordinate System

coordinate system that provides various methods to project the earth's spherical surface onto a two-dimensional Cartesian coordinate plane. Typically using feet or meters

Each geographic object in a vector layer - each city, river, lake, or country - is called a ______

feature

vector layers contain ________

features

UN Map

first version had 90 degrees west oriented vertically, now centers on 180 degrees, pointing upwards

three basic map types

general reference thematic special purpose

Geographic Coordinate System

global or spherical coordinate system such as latitude-longitude, typically expressed as Degrees Minutes Seconds (DD:MM:SS) or Decimal Degrees (DD).

Elements of Map Composition

map body inset/overview map title legend scale orientation/direction indicator map metadata

equidistant projection

map that maintains distance but distorts other properties

Dot mapping

one dot is set to be equal to a certain amount of phenomena, and ideally the dots are placed where that phenomena are most likely to occur

Conventional databases

only non-spatial entities

Conical projection example

perspective conic

Quantitative Data measurement

Ordinal (Categorization & Ordering) Interval (Ordering & Explicit Values, arbitrary zero) Ratio (Ordering & Explicit Values, non-arbitrary zero)

Planar projection example

Orthographic

Why do biases in maps matter?

People take maps at face value Influence decisions and behavior All maps represent some perspective

Spatial

Pertaining to the distribution, distance, direction, area, and other aspects of space on the Earth's surface

three basic map projections

Planar conical cylindrical

Point example

Point features: Monuments, points-of-interest, buildings, etc.

Featurescan take the form of _______________

Points, Lines and Polygons

Locations

Position in 2D space

Distortion

altering the size or shape of the earth's landmasses and graticule for projection to a flat or planar surface

Every Geographic Coordinate System includes

an angular unit of measure, a prime meridian, and a datum

Every Geographic Coordinate System includes:

an angular unit of measure, a prime meridian, and a datum

Model

an idealized and simplified representation of the world

Maps are an assertion of

power and administrative control

Visual Hierarchy

refers to the order of the graphical representation of your map information Helps in defining the figure-ground relationship

balance

refers to the organization of map elements and the empty space, resulting in visual harmony and equilibrium

Class

refers to the overall appearance of the graticule, once the projection process is complete Cylindrical, Conic or Planar

Case

relates to how the developable surface is positioned with respect to the reference globe Tangent or Secant

Databases

repository of structured information stored in tables of rows and columns.

Data model

set of constructs for representing objects and processes in the digital environment

Three Approximations of Earth

sphere, ellipsoid, geoid

You'll want to join two tables when:

the data in the tables has a one-to-one or a one-to-many relationship.

You'll want to relate two tables when:

the data in the tables have a many-to-one or many-to-many relationship

Layers are grouped by _____

theme

Rasterlayers contain a range of

values

_________ can take the form of optical, spectral and radiometric indicators

values

Layers can be ______ or _______

vector or raster

Make smart use of ___________ to make a map that is aesthetically pleasing and conveys the intended message effectively.

visual hierarchy, balance, contrast and colour

Relate

works with many-to-one and many-to-many relationships. Does not append tables. Instead, you can access the related data when you work with the layer's attributes.

Join

works with one-to-one and many-to-one relationships. Appends tables together into a new table.

Grid systems divided into ______ with only positive coordinate numbers (metres or feet)

zones

Isarithmic Map

(contour map) is created by interpolating a set of isolines between sample points of known values (example; contour map)

Each coordinate system is defined by:

-Its measurement framework, either geographic (3-D) or projected (planimetric) (2-D) -Unit of measurement -The definition of the map projection (for projected coordinate systems) -Other measurement system properties such as a spheroid (ellipsoid) of reference; a datum; and projection parameters like one or more standard parallels, a central meridian

Planar class

-Lines of longitude are straight, equally spaced that radiate from the center -Lines of latitude appear as concentric circles, centered about a point Again, The spacing of the parallels distinguishes one type of planer projection from another

Database Management System (DBMS)

-Manages the linkage between features and their attributes (i.e. the link between an object on the map and its description) -Manages interactions between clients and raw data -Manages different versions of data -Preserves data integrity -Provides secure access

Two Types of Data to be managed in GIS

-Spatial Data (where things are) -Tabular/Attribute data (what things are)

When would you use an Inset map?

1. To show a primary map area in relation to a larger more recognizable area 2. To enlarge important or congested areas 3. To show alternate thematic topics that are related to the maps theme, or different dates of the same theme

2 grid systems

1. Universal Transverse Mercator (UTM) 2. State Plane Coordinate System (SPCS)

Choosing the correct map projection

1. Which spatial properties do you want to preserve? 2. Where is the area you're mapping? Is your data in a polar region? An equatorial region? 3. What shape is the area you're mapping? Is it square? Is it wider in the east-west direction? 4. How big is the area you're mapping? On large-scale maps, such as street maps, distortion may be negligible because your map covers only a small part of the earth's surface. On small-scale maps, where a small distance on the map represents a considerable distance on the earth, distortion may have a bigger impact, especially if you use your map to compare or measure shape, area, or distance.

Waldseemuller Map

1507 - 1st map to depict Americas as their own continents - "BIRTH CERTIFICATE" of America

How many Spatial Relationships can be preserved or distorted by a particular map projection?

4 Relationship: area, angle, distance, direction Projection: Equivalent, or Equal Area, Conformal, Equidistant, Azimuthal Projections

grid system

A grid is placed over a map projection using a plane or Cartesian (x,y) coordinate system to locate features Created for larger scale mapping Divided into zones with only positive coordinate numbers (metres or feet) Easier to calculate area, direction and distance

Developable surface

A mathematically definable surface onto which the land masses and graticule are projected from the reference globe

Reference globe

A model of the earth at a reduced scale, that is used to project the landmasses and graticule onto a flat map

Reference map

A model of the earth at a reduced scale, that is used to project the landmasses and graticule onto a flat map

Raster

A representation of the world as a surface divided into a regular grid of cells.

vector

A representation of the world using points, lines, and polygons

Mercator Projection

A true conformal cylindrical map projection, the Mercator projection is particularly useful for navigation because it maintains accurate direction. Mercator projections are famous for their distortion in area that makes landmasses at the poles appear oversized.

What is chloropleth mapping suited to?

Abrupt Data Calculation of Typical Values (Ex. median income)

spatial queries

Adjacency Operations used to identify those features that "touch" other features. Containment Operations used to identify those features that "contain" or "surround" a set of target features

Spatial Queries are usually done based on two concepts:

Adjacency and containment

Robinson's guidelines

Conformal - Analyzing, measuring, recording angular relationships. Use for navigation, piloting, surveying Equivalent - Geographic comparisons across space. Use for thematic maps that represent proportions, either through color, or dot density Planar(Azimuthal) - Tracking the direction of movement Equidistant - Determination of distances

Advantages of mean (standard deviation)

Considers how data is distributed along the number line If data are normally distributed, then the Mean is a natural dividing point BUT ONLY works well for data that are normally distributed

Rasters are best for _____ data

Continuous

Disadvantage of natural breaks

Data ranges are usually uneven

Geographic Phenomena can be arranged along the following lines:

Discrete or continuous AND abrupt or smooth

Equal Intervals

Divides the range of attribute values into equal-sized sub ranges

Disadvantages of equal interval

Does not consider data distribution along the number line

Disadvantages of chloropleth mapping

Doesn't show variation WITHIN mapping unit Based on arbitrary boundaries

Cantino Planisphere

Early map of the Indies (Caribbean) and Africa made in 1502. It showed how skewed 16th Century Europeans' idea of geography was.

Quantiles

Equal numbers of observations are placed in each class

Pearson's guidelines

Equatorial Regions (0° to 30°N/S) - Cylindrical Mid Latitude (30°- 65°N/S) - Conic Polar Regions (Above 65°) - Planar

Disadvantages of quantiles

Identical Data values MAY be placed in different classes Again, fails to consider how data is distributed along the number line

attributes

Identity and Description. E.g. Qualities or Quantities, such as city names or population figures are stored in database tables often called Attribute Tables.

Dot mapping disadvantages

If you do not have access to ancillary information, such as satellite imagery, it is hard to have confidence in dot placement

Secant lines distortion

Inside secant lines: objects slightly smaller Outside secant lines: slightly bigger

Cold War Propaganda

It presents the USSR as looming over the world; it uses bellicose terminology such as "menace" and "vital" to enhance anti-communist sentiment. These maps use vivid images to create narratives supporting national interests by influencing the beliefs of their people.

when to use ellipsoid

Larger Scale maps of smaller areas

Conic class

Lines of longitude are straight lines of equal length, radiating from a central point (poles) Lines of latitude are concentric circular arcs centered around one of the poles Distinguishing Features -"Pie-Wedge"Shape -The angular extent of the wedge, and the spacing of the parallels distinguish one conic projection from another

Cylindrical Class

Lines of longitude are straight, equally spaced Lines of latitude are straight, parallel and intersect lines of longitude at right angels Distinguishing Features The spacing of the parallels distinguishes one type of cylindrical projection from another

DBs are used to

List, or Inventory Sort and order Compare Calculate & Synthesize

A GIS tracks ____ and ______

Location and attributes

The key function of a GIS is linking _____ to _______

Location to information

elements of all maps

Locations and Attributes

Cylndrical projection example

Mercator

Advantages of natural breaks

Minimizes the differences between data values in the same class, & maximize the differences between classes

Qualitative Data measurement

Nominal (Categorization)

Foreign Keys

Non-unique Identifier that carries information that may be linked to the primary key. often primary keys replicated in other tables and facilitate joins and relates between tables.

Queries

Primary method of data retrieval formed in SQL, are structured statements used to interrogate the database. Create new information from existing information, but won't change the older/existing information

Dot mapping suited to

Raw Data Totals

Proportional symbol map suited to

Raw Data Totals

when to use geoid

Reference surface for ground surveying of horizontal and vertical positions

Database Models

Relational Object-Oriented Object-Relational

Geodatabases

Requires assignment of Geographic or projected reference system upon creation. May be at the Feature Data Set or Feature Class Level

Queries are formed

SQL

Proportional Symbol Map

Scaling Symbols in proportion to the magnitude of the data around a central point. Can be used for actual or conceptual points.

Aspatial queries

Set Algebra <, >, =, <> Boolean Queries OR, AND, NOT

When to use sphere

Small scale maps, Countries, Continents

Isarithmic/Isopleth Mapping suited to

Smooth data totals

Considerations for Isarithmic/Isopleth Mapping

Standardization of Data Finer level of enumeration units more suitable

Considerations for chloropleth mapping

Standardization of Data (Unevenly sized Enumeration Units)

Data standardization

The numbers are distributed throughout the unit of analysis, and the size of the unit is taken into account. ie. raw data totals are adjusted for the size of the enumeration unit.

Mean: standard deviation

This classification scheme shows you how much a feature's attribute value varies from the mean.

Geometric interval

This is a classification scheme where the class breaks are based on class intervals that have a geometrical series An algorithm creates these geometrical intervals by minimizing the square sum of element per class Ensures that each class range has approximately the same number of values with each class and that the change between intervals is fairly consistent Produces a result that is visually appealing and cartographically comprehensive

primary key

Unique Identifier for EACH row of information a particular data file are unique and there is one for each record (row) in the database.

American Meridian

Used to determine State boundaries before Greenwich

Cloropleth Mapping

Used to portray data collected for Enumeration Units (counties, states, wards, districts etc)

Two types of GIS spatial data

Vector and raster

Grid systems

a grid placed over a map projection using a plane or Cartesian (x,y) coordinate system to locate features

spatial data model

a set of constructs for representing Geographical objects, data, processes, and relationships in the digital environment, for the purposes of analysis and complex problem solving

Isopleth Map

a special kind of isarithmic map in which the sample points are associated with enumeration units

Structured Query Language (SQL)

an international standard language for processing a database initially developed by the International Business Machines Corporation (IBM Corp) but is supported by a number of software vendors

Maps

are the visual representation of a spatial relationship between features

Features are linked to a row in the _______________

attribute table

In addition to location, features have _______ that identify and describe the features.

attributes

Aspect

deals with the placement of the projections center with respect to the earth's surface Equatorial, Polar, Oblique

datum

defines the position of the spheroid/ellipsoid relative to the center of the earth. (ie It defines the origin and orientation of latitude and longitude lines.)

Azimuthal

directions from a central point are preserved; usually these projections also have radial symmetry

Spatial Distribution of data

discrete or continuous abrupt or smooth

Disadvantage of Projected Coordinate System

distortion

continuous data examples

elevation, temperature, rainfall, etc.

Generic reference map

include various geographic features with no specific emphasis on any feature(s) or attribute(s)

Longitude

is an angular distance, East or West of a point on the Earth's surface, measured from the center of the earth

Latitude

is an angular distance, North or South of the Equator measured from the center of the earth

Cartography

is the making and study of maps in all their aspects

Relational databases make use of _____ to establish linkages between tables

keys

Grid systems created for _____ mapping

large scale

A map is made up of ______

layers

Relational databases

make use of keys to establish linkages between tables