CartographyDeveloping a Spatial Perspective

Developing spatial awareness Two interconnected concepts of objects

and measurements. Use objects to represent the real world,

which differ in:• size & shape• color & pattern• degree of importance• scale of measurement

Search for spatial order separates geography from other disciplines, we use a spatial language,

intellectual filter through which only the necessary information passes...

more than just verbal communication. developing an awareness of your spatial

environment

Spatial Elements observe type of objects encountered, real world spatial objects can be:• representative symbols:

points, lines, areas, or surfaces. points, lines, areas are stored within a GIS surfaces stored as point elevations, etc.

in a GIS, all data are explicitly spatial task is finding spatial surrogates.

Spatial Elements1. point features: trees, houses, road

intersections, etc.a. points are discrete; occupy a given

point in space at any time.b. spatial scale determines whether it’s a

point symbol or not. (point area)

Spatial Elements2. linear or line objects are “one-

dimensional,” a. unlike point symbols, we can describe

their shape & orientation examples: rivers, boundaries, fences.

b. spatial scale determines width.c. can measure them, unlike point objectsd. must know at least 2 points along line,

a beginning & end.

Spatial Elements3. areas are objects with length & width.a. “two-dimensional” objects: a yard,

areal extent of a city, a continent.b. series of lines beginning & ending at

same location.c. can describe their shape, orientation &

extent of territory occupied.

Spatial Elements4. surfaces are objects with length, width,

and height.a. “three-dimensional” objects: hills,

valleys, ridges, cliffs.b. location, area they occupy, orientation

(N/S, E/W), + third dimension height.c. surface features have infinite number of

height values: continuous

Surface features measure change in amount of height with

change in distance, so measure volume of material contained in

the feature itself.a. how much water in a reservoir?b. how much surface rock (overburden) lies

on top of a coal seam?

Spatial elements: summary

1. types of features & their locations,2. objects themselves are called entities,3. associated set of location coordinates,4. contain information about what they are

& how important they are to our study.

Spatial Measurements additional non-spatial information to help

describe object called attributes (ex. Trees) we can now indicate a feature, w/ a name, and

some measurable attribute, occupies a particular location.

but before we assign these attributes, we need to know how to measure them…

otherwise we can’t compare objects at one location w/ those at another location

Measurement Framework Levels of geographic data measurement, determined by partly by:

what we are classifying, what we want to know, and our ability to measure at a particular scale.

levels of “preciseness” vary from: general specific

Levels of geographic data measurement

• Nominal scale “named” data what to call an object but not able to

compare objects (church vs. fire station)• Ordinal scale list from best to worst uses only one characteristic to compare

Levels of geographic data measurement

• Interval scale numbers assigned to the items measured compared with more precise estimates of

the differences• Ratio scale most useful level of data measurement able to make direct comparison of two

spatial variables

Summary• Observe a wide variety of features,• Group them based on: scale we observed them, and whether they are points, lines, or areas.• Categorize them: four levels of measurement:

nominal, ordinal, interval & ratio.