What is spectral reflectance?
proportion of energy absorbed or reflected at various wavelengths
Why is white a significant color?
White is the benchmark or standard light
In what three ways is color quantifiable as?
Hue, saturation, value
What is hue?
dominant wavelength; black, red.
What is saturation?
Saturation is how pure the color is.
What is value?
What is spectral distribution?
What are sources of light in the physical world?
Why is poorly designed color confusing?
Visual clutter - nightmare
Misdirects attention. Can be misleading.
How can you devalue the information in a map?
Visual sophistication. 10 hues is TOO MUCH. Readers cant tell the difference.
Why is color blindness an issue?
5% to 7% of the population is color blind. Peter. Color blind people read maps too.
What is the difference between dichromats and trichomats?
Dichromat or Trichromat: types of cone cells
Dichromats are color blind people. Can only see two colors
What are hardware specified color models?
WHat is the RGB color model?
RGB - additive. Red green blue. Monitor display. Use this for your maps if on computer.
What is the cmyk color model?
CMYK - subtractive. Cyan magenta yellow black. Like painting. Add colors, get new ones. Use this for your maps if your printing it.
What are user specified color models?
HSV and Munsell?
What is the Munsell Perceptual Color System?
Human perception. Hue is the same. Value same as lightness. Chroma similar to saturation, related to perception. How pure color is.
What is HSV?
Hue, saturation, value. In order to implement this algorithm we had to address these six issues.
Arc gis uses hsv, cmyk, rgb.
Hsv is a perceptual system. Simplified munsell.
What are color wheel guidelines?
Opposite colors emphasize differences
Use equally spaced colors to underscore difference. Don't exaggerate difference.
Adjacent colors suggest harmony
What is hue?
The basic color
What is the value?
Value is the amount of white or black in the color
What is saturation?
Saturation refers to a color scale that ranges from a pure hue to gray or black
Pureness of the color: how wide the spectrum peak is
The amount of saturation gives us our shades and tints
What are monochromes?
Monochromes are a series of colors of the same hue with color values varied from low to high
How do you increase color contrast?
The greater the difference in value between an object and its background, the greater the contrast.
What are sequential schemes?
use lightness to represent ordered data
values increase as the darkness increases. Alcohol consumption lab.
What are diverging schemes?
combining hue and lightness
emphasizing the two extremes with darker color, and the average with the lightest color.
used to highlight a median, zero or threshold.
Works well with standard deviation classification
What are qualitative schemes?
combine various hues to show categorical data
a well-designed scheme should not suggest any ranking, or one color is more important than the other.
be alert for color associations that may be offensive. e.g., trying to use emphasized skin color to show race
What is the 4 color map theorem?
Given any map, at least four colors are needed to color the regions of the map, so that no two adjacent regions have the same color.
Why is the four color map theorem limited in cartography?
readers always try to interpret colors as some attributes, which is not the case. texas and ca are the same, lol no.
good for educational purposes to show different regions in an area.
What are general color guidelines?
Use monochromatic color scales most of the time.
Dichromatic scales suggest a middle-point
standard deviation classification
The darker the color, the more important the graphic feature
What should you do when using monochromatic scales?
In monochromatic scales, use more light shades of a hue than dark. The human eye can better differentiate among lighter shades than darker shades
When should you change symbol size?
Change symbol size instead of color values when there is a limited number of features
WHat should you do if you have a large number of polygons?
If you have a large number of polygons, consider symbolizing polygon centroid points with color instead of using choropleth maps
How is the abuse of color a common mistake in map making?
Most people can only distinguish between 5 and 8 colors on a given map.
Not as pretty as you imagine.
Color printing is expensive!
Your map may be reproduced in Black and White
What is the Miller shape measurement?
coefficient of compactness
c=area/area of circle ,
where the irregular shape
and the circle have the same perimeter.
Problem with this is you can have 2 very distinctive shapes but the coefficient is the same.
What is the Bunge shape measurement?
set of distance measurements taken between systematically placed vertices on the perimeter
Originally applied to 97 Mexican community
Outlines. How socioeconomics are correlated with outlines
How do you perform Bunge's shape measures?
Select vertices on shape
Take shortest straight-line distance between different pairs of vertices
Pick a start point and a direction (e.g. clockwise)
Repeat for all start points
Then repeat skipping one, two, three, etc points at a time
Values are unique for any specific shape
What are the problems with shape measures?
Shape can vary by scale and projection!
Many violate the one shape one number rule
All violate the number to shape rule
Many simply compare one shape to another, e.g. a circle
Shape is often multi-dimensional (Bunge)
What is symbolization?
Symbolization is the process of assigning colors, markers, sizes, widths, angles, transparency and other properties to features.
What are 3 types of symbols?
Point, line, polygon
What do points represent?
Points represent things at a small scale.
WHat do polygons show?
Polygons show regions, city regions, natural regions.
What is perspective height?
useful when you use height to show property you are trying to show. X and y plane can be mapped. Points show a persons location at different times. Time and height. Time geography. Show a daily projectory over space and time. Stronger the distortion, more population the region has. Psuedo 3d can be a peak in population in the map. Population geography.
What are measurement scales?
What are data types?
- Discrete (hard edges)
Points, lines, areas
- Continuous (soft edges)
How do you symbolize nominal data?
Values are discrete (that is, mutually exclusive) and are classed according to type or quality. For example, a line could represent either a road or river, and a land use polygon could be residential, commercial, or a recreational area.
How do you symbolize ratio data?
The values from the ratio measurement system are derived relative to a fixed zero point on a linear scale. Mathematical operations can be used on these values with predictable and meaningful results. Examples are age and distance
How do you symbolize ordinal data?
Ordinal values determine position. These measurements show place, such as first, second, and third, but they do not establish magnitude or relative proportions. It is not possible to measure the differences between ordinal data.
What are thematic maps?
Proportional Symbol Maps (aka Graduated Symbol)
Area Qualitative Maps
Dot Density Maps
What are proportional/graduated symbol maps?
The proportional size of symbols represents the value of the attribute.
These maps scale icons (most often circles) according to the data they represent.
Simple symbol, size changes in proportion to data
Represents relative magnitude AND concentration
When should proportional symbol mapping be used?
Place-specific information - deaths per county
- Illustrate varying concentration = population
- Map design differ for both of the above
What is true point data?
Data are measured at specific point locations. Cholera map.
What is conceptual point data?
Data are summarized within areal (or volumetric) units
What is mathematical scaling?
data values directly related with symbol area, i.e., if one value is twice as large as another, its circle is too. Other symbols with known area equations can be used.
What is perceptual scaling?
Perceptual: overcomes the underestimation of large symbol values.
What is range grading?
Grouping raw data into classes and representing each class with a different sized symbol
What are the pros of range grading?
Easy to discriminate symbols and match to legend, contrasting sizes may enhance the map pattern.
What are the cons of range grading?
Readers may misinterpret information if they do not pay close attention to the legend
What are the design principles for symbols?
Avoid range grading if data range is small.
Preserve visual contrast
Avoid volumetric symbols (e.g., spheres, cubes)
Circles are the most common (expected) symbol
Why are circles the most common symbol?
What are geometric symbols?
Circles preferred because they are visually stable and conserve map space.
What are pictographic symbols?
Eye-catching, but difficult to estimate their size.
What is the difference between nested legend arrangement and linear legend arrangement?
In the nested legend arrangement, a large circle includes a smaller one in sequence, takes less space
while in the linear legend arrangement, the circles are aligned vertically or horizontally in the
ascending or descending order.
What are point symbol guidelines?
Size: Large symbol = higher data value
symbol may be larger or smaller than the polygon area it represents
Location: Placed within the center of the area they represent
Proportioned symbols give a fairly exact understanding of differences in magnitude
Graduated (range graded) symbols can be easier to interpret by the reader
Use pictograms when they "make sense" (i.e. picnic areas, camping locales), but do not expect the reader to have to interpret them.
Ensure that symbols are readily identifiable and look markedly different from each other.
Symbol angle or orientation should be used to denote direction
What are line symbol guidelines?
Width: Wide = higher data value
Like point symbols, line symbols can be proportioned or graduated, graduated symbols are used more. Harder to interpret width of a line.
Dashed patterns: wider spacing creates coarser textures
Line Casing, like text halos, can increase line visibility over background.
What are area symbol guidelines?
Abstract or Realistic symbols available: ensure obvious logical relationship between symbol and data.
Loosely spaced textures suggest small values; tightly packed textures suggest large values. Want textures to be meaningful.
Alter color lightness/darkness to enhance hierarchy . Darker is higher value.
What is the visual variable suited to representing ordered data?
Lightness, saturation, and size are the visual variable suited to representing ordered data. These variables establish hierarchy among features.`
What should symbolize quantitative data?
Perspective, height, transparency and focus can also help to symbolize quantitative data.
What should represent qualitative data?
Hue and shape are the visual variables suited to representing qualitative (categorical) data
What are chloropleth maps?
Numerical data is classified into categories and the categories are shaded. Polygons are often based on politically defined feature.
This will yield a display that puts visual emphasis on the largest area units of the map.
Color-coded polygons or patterns showing different values
What is normalizing data?
Divides one numeric attribute by another in order to minimize differences in values based on the size of areas or number of features in each area
What are isopleth maps?
The concentration of an attribute is represented by connecting points of identical values to create lines.
What are isopleth maps ideal for?
Ideal for continuous area data (i.e. data exists at every point) that varies smoothly over space. It does not change abruptly at any point (like tax rates do as you cross into another political zone).
What are area qualitative maps?
Shows the distribution of pre-existing geographic classes (soils, land-use, vegetation, etc.)
Use textures, but avoid texture vibration
Be careful with hues do you don't create ranking implications
What are dot density maps?
Dot maps create a visual impression of density by placing a dot or some other symbol in the approximate location of one or more instances of the variable being mapped.
What are dot density maps used to represent?
Used to represent themes that vary smoothly over space but are discrete.
What do conformal maps do?
What do equivalent maps do?
What are guidelines for map projections?
We can customize where and how much error is in a projection
We can know and display the error
Always include information about the projection
The smaller the extent the map covers, the less overall distortion
What is the universal transverse mercator projection?
Common projection. Higher the latitude the higher exaggeration it is in mercator projections, why it doesn't include poles.
What does the universal transverse mercator projection cover?
60 zones cover 84 degrees N to 80 degrees S
Takes advantage of the Transverse Mercator projection's properties
Distortion is minimized along a central meridian that goes from pole to pole, in each zone.
lines of true scale are located approximately 180 km on either side of, and approximately parallel to, the central meridian
UPS Polar stereographic projection covers the poles
6 degrees per region. Area preserved, shape preserved.
What is in each UTM box?
There is a central meridian in each box. 180 km from central meridian for no distortion.
What are state plane coordinates?
Works only in the US and territories
Old system based on NAD27 and feet shown on many USGS maps
New system based on NAD83 and GRS80; uses slightly different zones and meters
Each state works independently
More accurate than UTM, used in surveying and engineering
What is metadata?
data about data
When you download the raw data, there usually is a .txt file describing the attributes.
You can also browse and edit it in ArcCatalog (special features in ArcGIS10). Every fxn with metadata. Add layers. Sometimes description tab wont work so go to customize, arc catalog options, metadata tab, change to iso something something
How do you change the projection of a layer?
To change the projection of a layer, use "Define Projections" in the Arc Toolbox.
What projection is used for surveying applications?
State Plane projection used for most surveying applications. Most of our data anyway.
What is mobile gis?
Positioning systems commonplace
Location Based Services
What is a digital earth?
Open Geospatial Consortium (OGC) and the International Organization for Standardization (ISO)
Volunteered Geographic Information (VGI)
What is volunteered geographic information?
volunteered geographic information (VGI), a special case of the more general Web phenomenon of user-generated content
What are the three types of sensors?
a network of static, inert sensors designed to capture specific measurements of their local environments.
sensors carried by humans, vehicles, or animals
humans equipped with sensors and with the intelligence to compile and interpret what they sense, and each free to rove the surface of the planet.
What are the issues of using humans as sensors?
The digital divide: access to internet
Loss of anonymity
What are visual interfaces?
GUI and WIMP (windows, icons, menus, pointer)
Perceptual and multimodal interfaces
User centered design, "cognitive engineering"
What are some unsolved problems in volunteered geography?
Spatio-Temporal Maps (4D Maps)
What is fusion?
aggregation, integration and conflation of geospatial data across time and space with the goal of removing the effects of data measurement systems and facilitating spatial analysis and synthesis across information sources
What is visual imagery?
Visual imagery refers to the ability to visualize, that is, the ability to form mental pictures, or to "see in the mind's eye". Marked individual differences have been found in the strength and clarity of reported visual imagery and these differences are of considerable psychological interest
What is the aim of the visual imagery test?
The aim of this test is to determine the vividness of your visual imagery. You are asked to rate the vividness of each image by reference to the 5-point scale given below. For example, if your image is "vague and dim" then give it a rating of 4. After each item write the appropriate number in the box provided. The first box is for an image obtained with your eyes open and the second box is for an image obtained with your eyes closed. Before you turn to the items on the next page, familiarize yourself with the different categories on the rating scale. Throughout the test, refer to the rating scale when judging the vividness of each image. Try to do each item separately, independent of how you may have done other items.
What is the visual imagery rating scale?
The image aroused by an item might be:
Perfectly clear and as vivid as normal vision rating 1
Clear and reasonably vivid rating 2
Moderately clear and vivid rating 3
Vague and dim rating 4
No image at all, you only "know" that you are thinking of an object rating 5
What does a high vviq suggest?
High VVIQ suggests that you are a verbalizer
What does a low vviq suggest?
Low VVIQ suggests that you are a visualizer
What are the steps of the design process?
Determine how the map will be reproduced
Select scale and map projection for map theme
choose the proper datum (often NAD83 if you are mapping the continental US)
if combining layers with various projections, re-define all maps to one projection (seamless).
Determine method for symbolization and classification
Select map elements to employ
Establish ranking system of symbols and map elements according to their importance
make the most important elements eye-catching
Create sketch maps (hand drawn the layout)
Construct the map
Evaluate/Edit the map
What is a graticule?
grids formed by latitudes and longitudes. good to show shape distortion. It works well as the frame when you make small-scale map, e.g., the map of continental U.S., or the maps of CA
What is figure-ground?
Accentuate one object over another, based on the perception that one object stands in front of another
What is contrast?
The visual distance between map features that allow us to distinguish one from another
What is balance?
Organize the map elements and empty space so as to achieve visual harmony and equilibrium
What does your eye expect from a visual layout?
Eye expects (1) balance and (2) alignment
What are the indicators of typographic hierarchy?
Point Size (Font Size)
Scaling: Extended/Condensed (Kerning & Leading)
Color Lightness: Lighter type fades to background
Case: Uppercase = Importance
What are the design principles of typography?
Font Types: Serif (times new roman), Sans Serif(arial), and Display Fonts
Kerning: Space between letters
Leading: Space between lines
Typographic Effects: Masks, Callouts, Shadows, Halos
What are typographic guidelines?
Avoid decorative fonts and use bold/italics sparingly
Avoid using more than 2 type families on a map
All type must be readable: choose a realistic lower limit for all font sizes
Type size should correspond with size/importance of map features
Do not passively accept default font choices
Orient type horizontally (with exceptions)
Place labels so they are associated with features they represent
What is point label placement?
Avoid overprinting of underlying graphics according to sequence of "preferred locations" (See Slocum Fig. 11.23A)
If the above is not possible, consider halo, mask, etc.
Do not allow features between symbol and label
Symbols on land that are close to water should be placed entirely on land feature
Do not exaggerate kerning or leading on point symbols
If necessary, leader lines should not touch feature
What is line label placement?
Place type above the features, but not touching them
When labeling complex linear features, follow general trend of the feature. e.g., river
Very long features can be labeled more than once
Labels should always read from left to right.
What is area label placement?
When possible, visually center the label within the feature
Consider using all-uppercase type for emphasis
Exaggerated kerning and leading most effective with all-uppercase type
Areal features that are too small to contain a label should be labeled as if they were point symbols (See Slocum Fig. 11.23A)
If necessary, leader lines should be thin, not include and arrowhead, and just enter the feature
What are the British Cartographic Society's principles of cartographic design?
Concept before Compilation
Hierarchy with Harmony
Simplicity from Sacrifice
Maximum Information at Minimum Cost
Engage the Emotion to Engage the Mind
What are Chernoff faces?
display multivariate data in the shape of a human face.
individual parts(eyes, ears, mouth and nose) represent values of the variables by their shape, size, placement and orientation.
What are the three types of cones in the retina?
Red, green and blue
What is the opponent process theory?
Three channels are involved in color perception: lightness-darkness channel, red-green channel, blue-yellow channel.
What are perceived colors?
FUnction of a mix of colors in the opponent channels
What is color vision impairment?
Inability to discriminate between red and green colors
What is simultaneous contrast?
Perception of color might be afunction of the colors that surround it
What is the difference between soft copy and hard copy maps?
Soft copy uses RGB and hard copy uses cmyk
What kind of map should you use if the data is smooth and continuous?
A contour map
Why is data standardization important?
Raw totals need to be adjusted to account for the area over which the data have been collected
What do larger scale maps have?
What do smaller scale maps have?
What are two processes that reduce detail on maps?
What is map generalization?
the systematic reduction of detail to enhance the point of your map
What is data classification?
the systematic categorization of detail to enhance your map
What is displacement?
Moves features which interfere with each other apart. Sacrifices location accuracy for visual clarity.
What is a quantile scheme?
Quantile schemes place the same number of data values in each class. Always produce distinct map patterns. Often place similar values in different classes or very different values in the same class.
What are three types of symbols?
Symbol by relationship, resemblance, convention
What are basic map symbolization issues?
Different kinds of data, visual variables, and symbolizing aggregate data
What is shape a good choice for?
Showing qualitative data