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101 Cards in this Set
- Front
- Back
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Cartography |
Art and science of making maps. Requires study of philosophical and theoretical bases and rules for map making, map communication |
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Mental Map |
Mental images with spatial attributes |
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Tangible maps |
Paper maps, and virtual maps. Maps of counties, states, etc. |
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Thematic map elements |
1. Base map-geographic reference 2. Thematic overlay 3. Set of elements- legend, title, scale, etc. |
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Base map |
Provides reference for thematic overlay. Specific geographic area. |
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Thematic overlay |
Simplicity and clarity Includes descriptive information
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Types of Thematic maps |
Choropleth Dot map Proportional Symbol Isarithmic & 3D Cartogram Flow Map |
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Choropleth |
Data is in enumeration units-like population density |
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Dot map |
Shows variations in spatial density- peanut acreage |
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Proportional symbol |
symbols are scaled to values at points. Tornados in central OK. |
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Isarithmic & 3D |
Continuous volumes- elevation, temperature, precipitation. Also called isolines. |
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Cartogram |
Enumeration units values replaced by variable being represented. (by size, etc) Cannot make in ArcGIS. |
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Flow Maps |
Show linear movement between places |
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General purpose maps |
Display objects from geographical environment. |
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Thematic maps |
Special purpose Show Qualitative or quantitative data |
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Qualitative map |
Spatial distribution or locations of single theme- nominal data. No quantities displayed. Ecoregions, geology, soil, etc. Show how much or to what degree something is present in mapped area. |
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Quantitative |
Show spatial aspects of numeric data. Usually single variable- corn, people, income. Variation from place to place. Is the transformation of tabular data into spatial format. |
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Map scale |
Scale selection is most important decision cartographer makes. Ratio of map distance over earth distance |
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Large scale |
Large in detail, small in area |
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Small scale |
Small in detail, large in area |
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Map Communication |
Map author- constraints include- purpose, format, scale, symbolization, graphic/printing limitations, economic considerations, etc. |
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Map percipient |
Gains spatial knowledge |
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Thematic maps |
designed with audience in mind Match interest and knowledge
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Map Use |
Interaction-reading, Differentiates patterns- analysis Desire to explain patterns-interpretation
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Cartographic Abstraction and Generalization |
Process of transforming unmapped data into map form Selects/organizes information necessary to develop user's understanding |
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Selection |
Involves early decisions regarding geographic space to be mapped, map scale, projection, aspect, data and sampling process. Map maker must be familiar with map content before beginning |
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Classification- |
Process in which objects are placed in groups having identical or similar features. Individuality of each element lost. Reduces the complexity of map image. Organizes map information. Enhances communication. |
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Simplification |
Selection and Classification- examples of Smoothing of natural or man-made lines to eliminate unnecessary detail. Path might be straightened to show connectivity not precise features. |
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Symbolization |
Linking spatial information to descriptive information Replicative- designed to look real Abstract- geometric shapes |
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Definition map design |
Aggregation of thought processes cartographers go through in process of map making. Includes scale, projection, symbology, typography, color, etc. Functional relationship between map author and user. |
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Ethics in cartography |
Page. 19-20. Maps made by humans may contain purposeful errors, errors of oversight, and/or poor judgement. |
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Chapter2- Geodesy, Coordinate Systems, Scale |
Geodesy- science of Earth measurement
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Projection |
Allows cartographer to project curved surface of earth on flat map. |
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Map projections |
cause distortions- size,(distance & area) Shape, Direction |
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Shape of Earth |
Ellipsoid Approximately sphere, but has many depressions and bulges |
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Projections |
NAD27- 1927 Clarke ellipsoid of 1866 NAD83-US adopted GRS80 Datums-starting point-gives context to locations and heights on Earth's surface |
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Plane Coordinate Geometry |
Plane Coordinate Geometry Earth coordinate geometry |
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Plane Coordinate Geometry |
Cartesian coordinate geometry- system of intersecting perpendicular lines on a place containing two axes- x, y. |
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Earth Coordinate Geometry |
Based on Plane geometry Referred to as eastings(point along x-axis) and northings- (point along y axis) Read right up- |
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Earth Coordinate Geometry |
Latitude/Longitude- (DMS and DD)
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Latitude |
Runs East/West Angle to the center of earth from equator |
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Longitude |
Runs North/South British Royal Observatory- in Greenwich fixed reference line- Prime Meridian for longitude. Has designation of 0 degrees. Opposite side of PM is International Date Line (not a straight line). |
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Chapter 3- Map Projections |
Project latitude and longitude onto flat surface Only practical way to portray Earths curvature on flat surface. |
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Projection Families |
Azimuthal Cylindrical Conic Mathematic |
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Azimuthal |
spherical grid projected onto plane. Projected from a pole.- paper touching one point(tangent) or secant(passing through). Normal aspect is polar position. Popular during WWII. Adjustments in light sources common. Center of globe- gnomonic opposite tangency- stereographic theoretical infinity-orthographic |
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Cylindrical |
Used in medium/large scale wrap flat sheet onto cylinder Equatorial aspect- normal Scale preservation in east/west Distortion increases toward poles |
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Conic |
Constructed by transferring graticule from globe to cone enveloped around sphere. Secant conics compress scale between standard lines and exagerate elsewhere. |
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Map Projection Properties |
Equal Area Mapping- all parts maintained equally Conformal mapping- angles preserved. Meridians intersect at right angles and scale is same in all directions. shapes for larger areas may be distorted. |
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Map Projections Properties |
Equa-distance mapping = preservation of great circle distances. Sometimes used in general pupose maps . Neither conformal nor equal area. Have less distorted appearing land masseses. |
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Map Projections Properties |
Azimuthal- Directions from central point to other points are accurate. Not exclusive. Can occur with equivalency, conformality, and equidistance. |
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Minimizing distorition |
Equal area- area conformal- shape equidistance- distance azimuthal- direction |
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Coordinate systems |
UTM- Universal Transverse Mercator SPC- State Plane system |
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Chp. 5- Descriptive Statistics & Classification |
Data processing Mathematical and statistical methods |
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Data processing |
Analyzing and preparing geographic data for mapping. One way to reduce them into forms more suitable for straightforward communication. ` |
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Mathematical and Statistical |
Express magnitudes and relationships in terms of numbers Summarize observations Describe relationships between variables Make inferences both estimations and tests of significance. |
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Ratio |
Express relationship between two data entities Population density # of people per sq. mile |
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Proportion |
Ratio of number of items in one class to the total of all |
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Summarizing Data Distributions |
Purpose- develop one best numerical description for data set three ways to use- Central tendency-Basic Distribution of data Dispersion- dispersion of data Shape-nature of distribution- skewness, kurtosis |
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Central Tendency |
Mode- One that occurs most Median- Midpoint of data Mean- Average |
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Dispersion |
Variance Standard Deviation
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Normal Distribution |
Characteristics: symmetrical (bell-shaped curve) Mean, median, mode are same Unique probability distribution- |
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Normality Measures |
Skewness-measure of displacement= when peak or mode of distribution is not in the middle Kurtosis- measure that describes peakniness of distribution (normal is 3.0) |
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Data Classification |
Why- reduce large number of observations to smaller groups to facilitate description Help define and detect phenomena |
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Classification is |
provides more interpretive power many data classification schemes/methods |
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Best Classification |
natural break/=interval ratio |
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Session 11 Statistics and Data Classification |
Classification leads to loss of detail, provides more interpretive power. |
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Raster/Vector |
Vector- more precision with boundary lines Raster- lose information, sacrifice original polygons |
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conversion of formats |
Unavoidable Vector to raster- cannot get precision Defend vector to raster. |
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Choropleth |
Level of measurement data classification symbolization base map development |
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# of classes |
Nothing sacred about 4 or 5. Statistical classification of ordinal and interval/ratio data unrestricted mathematically |
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Classification Schemes |
Include all data ranges no overlapping nor vacant classes great enough to avoid sacrificing accuracy but not so great as to impute divide into reasonably equal groups logical mathematical relationship |
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Choropleth Considerations |
Polygon or areal units- should be on definite enumeration units. Interval ratio data- can be totals or derived value Scale consideration- insensitive to changes of variable that occur at large scales .
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Best Classification method |
Natural breaks |
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Quantiles |
focus on quantity every class has same # of occurrences even distribution of colors |
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Equal interval |
size of each subgroup is same |
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Standard deviation |
second best approach if you do not have natural breaks. |
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natural breaks |
minimize difference between homogeneous cases within single group maximize difference between groups Jenks optimization |
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Arithmetic and geometric intervals |
produce class boundaries and intervening distances that change systematically. Should be used only when graphic plot of mapped values tends to replicate mathematical progressions |
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Data truncation and outliers |
Extreme observations treated as outliers and given their own class. Outliers removed or separated from data set. |
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Dot density maps |
mapping discrete geographic phenomena communicate spatial density dot can represent one to one or one to many legends important |
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Choose appropriate symbol |
represents each discrete element of geographically distributed phenom Symbol does not change, but its number changes from place to place one to one one to many |
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One to many |
determine dot value (2-3 dots for areal unit with lowest value) determine quantity of dots- divide value of areal unit by dot value dot placment- done in random fashion |
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Advantages of Dot |
easy to understand illustrates spatial density more than one data set can be illustrated on map fast computation |
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Disadvantages |
map interpretation is not one-to-one perception of relative density is not linear time consuming if done by hand difficulty for map readers to recover original data values |
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Proportional symbol |
Conceptual basis- size of point is in proportion to quanitites it represents Circles most often used- compact, visually stable, scaling less difficulty Avoid 3D symbols |
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when to use Proportional |
data occur at point locations data are aggregated at points within areas goal of map is to show relative magnitude of phenomena at specific locations |
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Proportional Symbol scaling |
Psychophysical effects-length is correcly perceived Area and volume are usually underestimated volume is more underestimated than area Perception of circles among circles
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Scaling methods |
absolute- true to scale Apparent magnitude scaling- scale is not true- make larger symbols to avoid underestimation. |
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General Guidelines |
misuses of proportional - data variation is small 3D symbols used Symbol overload Good practice- range grading- similar to choropleth transparent circles |
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Symbol size determination |
Determine relationship between quantity and symbol size= identify geographic entity with lowest value decide smallest symbol size convert smallest symbol size to symbol representing that quantity |
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Determine symbol size for other entities |
divide entity's value by lowest value multiply quotient with smallest symbol size convert derived symbol size to symbol |
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Isarithmic |
conceptual basis= three dimensional graphical volume with quantitative line symbols |
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Types of isarithmic |
Isometric- composed of isolines whose known Z values sampled at point locations Isoplethic-composed of isolines whose known Z values are recorded for polygonal areas rather than specific points. Centroids, or centers can be calculated. |
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When to use Isarithmic |
data in form of geographical volume must have surface that bounds volume mapped phenomena continuous in nature distribution must be fully undrestood in order to map it correctly |
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Elements of Isarithmic |
data points and datum iterpolation methods isarithms isarithmic intervals |
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Cartograms |
value by area maps are unique representations of geographical space
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Major problems with Cartograms |
no base map nor projection area measurement represents quantity distance, direction cannot be correctly measure spatial relationships among features distorted difficult to read and understand
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Advantages |
Boundary and orientation relationships maintained reader need not supply missing areas shape preserved |
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Disadvan |
distortion of boundary and orientation can be so great link with true geographic space becomes remote and may confuse shapes of internal enumeration units distorted and make recognition impossible |
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Use of |
communicating Recognizing shapes estimating areas Inset map important two-variable cartograms
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Creating |
Time consuming
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