Module 6 Flashcards
The main goal of any map
the goal of any map is to communicate the spatial information portrayed on the map as effectively and efficiently as possible – reading a map should be both an enjoyable and enlightening experience
The Cartographic Process:5
- think about what the distribution of phenomenon might look like
- decide on the purpose of the map and the intended audience
- collect data that are appropriate for the purpose of the map
- what projection would be best - design and construct the map using appropriate cartographic principles
- determine if the map reader understands the map content
the most important components of the map is the..
..the spatial data itself, which should be the focus of the product; surround it with secondary components
the legend is the 2nd most important component of the map –the legend is the tool by which you interpret the symbols that display the data
geospatial metadata
▪ geospatial metadata provide information about the data used to create the map or perform GIS analysis
▪ it can be used to represent the who, what, when, where, why, and how of the resource
▪ when maps are produced from a variety of different data sources, or if the data has undergone substantial manipulation, documenting the geospatial metadata is even more important – known as geo-lineage
▪ in practice, very few maps provide this information hindering the ability of the map user to fully understand the potential limitations or benefits of the map
in 1854, John Snow produced one of the most important _____ maps, using black bars to identify the location of each death due to cholera in London – the high point density on Broad Street led to the discovery of a central source of the outbreak
point
apparent (perceptual) scaling vs absolute scaling
tries to take into account the human tendency to underestimate the size of larger circles
method with suggests that only the actual zscore should be presented because it accurately represents the data
▪ the argument here is that cartographers should tell the truth and exclude compensation for human perception failings
flow maps
flow maps use proportional line symbols to represent the scale of a phenomena as it moves through a linear network flow maps use proportional line symbols to represent the scale of a phenomena as it moves through a linear network
- The thickness of the line is used to represent the z-value, and can follow the same sizing approaches as used for point data
- The thickness of the line is used to represent the z-value, and can follow the same sizing approaches as used for point data(
Isarithmic mapping
uses isolines(lines of equal value) to model smooth, continuous phenomena
isopleth maps
▪ isopleth maps use conceptual data points to create statistical surfaces – although they look like isometric maps, they are created in a different way
-have to come up with a rate, like #people/km, so that its equal across geographic locations
▪ in any isoline map, the choice of the isoline ______ is important – it is analogous to the spatial resolution of raster data or digital imagery
interval
▪ too few isolines will miss important details, and in places of small difference may be so widely spread apart that the reader can’t notice their importanc
.too many isolines will result in redundancy and clutter on the map
chloropleth mapping
choropleth mapping is performed by mapping spatial data that are constrained to lie within a definable administrative unit
▪ the size and shape of the administrative units can create special problems when performing choropleth mapping – large units tend to dominate over smaller units – good choropleth maps try to keep the units roughly the same size
▪ when keeping the units similarly sized is not an option, Standardization can be used to take into account the size of the administrating unit
the natural breaks method
the natural breaks method examines a histogram of the original dataset to determine logical breaks (often seen as gaps) in the data distribution
equal interval method
▪ the equal interval (or equal steps) method forces each class to occupy an equal interval along the x-axis when the data are arranged in histogram form ▪ when it is not necessary to include specialized natural breakpoints, it is good cartographic practice to create all of the class intervals so that they have the same width
Quantile method
▪ the quantile method ranks and orders the observations in the dataset and then places equal numbers of observations in each class
▪ if 4 classes are used, then it is a quartile map; if 5 classes are used, then it is a quintile map, etc.
mean ± standard deviation method
▪ the mean ± standard deviation method creates class boundaries by repeatedly adding or subtracting the standard deviation from the mean of the dataset
