Maps Flashcards
three principles for designing maps
- focus (who the map is for)
- simplicity (what data is needed what isn’t?)
- think cross disciplinary
what does a map represent
spatial data that provides a reader with information
can maps be abstract
YES - can be ideas or concepts
are maps considered a model
YES
are maps truthful
NO - all maps are wrong
what is cartographic generalization
the simplification of representing items on a map
does GIS data have a map scale before or after map is printed
AFTER printed
what controls generalization
scale
what are two ways of generalization
- line simplification
- reduction of spatial complexity
how can curves on a map be simplified
by using a subset of the original points
how can features be moved to increase clarity
smoothing them (make straight lines smooth and remove elements that aren’t needed)
geographic scale
real world size or area of a feature
relationship between objects on ground to geographic scale
larger ground objects = larger geographic scale
map scale
a value representing the number of units on a map relative to the number of same units on the ground
what is representative scale
the number of units on a map : the number of SAME units on the ground
what are three ways a map scale can be represented
- representative fraction
- verbal
- scale bar
do representative fractions have units
NO
scale bar
a graphic representation of the map scale
what is the best option for scale on a map
scale bar
large vs small scale map
large scale: maps showing SMALL geographic region with LARGE representative fraction value
small scale: maps showing a LARGE geographic region with a SMALL representative fraction value
are features on a small scale map large or small
small
are features on a large scale map large or small
large
large or small scale map
large
large or small scale map
small
accuracy vs precision
accuracy: degree for which information matches the true value
precision: the level of exactness/repeatability of a dataset
is accuracy or precision “how far the data is from the reference point”
accuracy
is accuracy or precision “the distribution of data around a mean value”
precision
what is the standard mapping accuracy
0.5 mm
what happens to the area of uncertainty as the scale increases
area of uncertainty increases as scale increases
what are some purposes for maps
- reference map
- thematic map
reference map
a map that shows where geographic features are relative to each other
topographic map
designed to convey information about a single topic
type of map
thematic
type of map
reference
contrast points , polygones and lines
points
- no area or length
polygons
- has area
lines
- has length
what is symbology
set of conventions that define how geographic features are represented with symbols on a map
what does symbology refer to
the size, shape and colour of symbols used
why are single symbol symbology used
show one set of data (where things are)
why are unique values used for symbology
show contrast between features in different categories (embassy by colour for each country)
what are graduated color symbology
features are placed in classes based on numeric values (shows density)
why is classification used in maps
- for quantitate data
- when applying graduated symbology
three types of classification
- natural breaks
- equal interval
- quantile
pros and cons of natural breaks classification
pro
- good for mapping uneven distribution
cons
- not good for comparing data
- difficult to find the proper number of classes
pros and cons of quantile classification
pro
- provides understanding of relative position
cons
- similar features can be placed in different classes
- widely different features can be placed in the same class
pros and cons of equal interval classification
pro
- best for values such as percentage or temp
cons
- prone to issues with clustering
- not ideal of uneven distribution
why is normalization used in maps
it creates a ratio map, allows for comparison between different areas
