Lec 2: Reality, Data

“Art is a lie which makes us realize the truth” (Picasso)

Quote from the Introduction to Part I of the book

Do you want to understand Part I — on “Map Reading” and its 10 Chapters?

If so, then read the Intro to Part I (pp. 17-18)

To quote from Paragraph 2 on p. 18:

“Since the exact duplication of a geographical setting is impossible, a map is actually a metaphor. The map maker asks the map reader to believe that an arrangement of points, lines, and areas on a flat sheet of paper is equivalent to a multidimesional world in space and time. For full meaning, the map reader must go beyond the paper-and-ink representation to the real world referents of the system.”

Is this true?

Since Chapter 1 is about The Environment to be Mapped

let’s look at an environment and at a modern map of that environment

... and assess the validity of the quoted assertion

Saline Valley slideshow versus a “modern map viewing experience”

So what’s the verdict?

Discussion

Today’s Lecture

Geographic Reality

Geographic Data

Geographic Reality

The Physical (or “Material”) World

The concept of a geographic feature

a “geography as geometry” point of view

Feature hierarchy

Declarative

Object

physical (eg. “bridge”)

conceptual (“soil type”)

Relation

derived, form/pattern, spatial arrangement (eg. “centroid”)

Procedural

Process (eg. “air mass flow”)

has temporal component

Form

Discrete

Dispersed/Discontinuous features

Continuous phenomena

Discrete (Figs 1.1., 1.2)

Fig 1.1.

Fig 1.2

Dispersed/Discontinuous features

E.g.:

Rock Outcrops

Park Forest

Houses in a village

and other “salt or pepper” distributions

Continuous phenomena (Figs 1.4 - 1.7)

Mosaic, Stepped, or Smooth surfaces

Mosaic surfaces

w/distinct border (rare)

w/continuous transitional boundaries (more common)

Fig 1.4

Fig 1.5

Stepped surfaces

terraces

nature tends to smooth gradual transitions

Fig 1.6

Smooth surfaces

eg. elevation

environmental gradients

Dimensionality of Environment

Fig 1.9

Quote p. 26 para 2

“We learn early that objects have three dimensions: length, width, and height. If all three dimensions are 0, we have a 0-dimesional (point) object. If two dimensions are 0, we have a one-dimesional (linear) feature. If only one dimesion is 0, we have a two-dimensional (area) feature. If an objects exhibits all three dimensions, we have a three-dimensional solid (volumetric) feature. In geographical terms, length and width become area or region, and height becomes elevation or magnitude.”

dimensions

0-3D

fractals

T

Fig 1.10

Environmental Change

spatio-temporal context

static vs. dynamic feature

depends on/relative to a temporal scale

The Nature of Time

T is relative

natural time

biological time

clock or calendar time

...and their importance in Aviation

Enviromental Temporality

Change of Environmental Features

change in State

change in Position

rate of change

Quote (pp. 28-29)

“Things that happen too fast we miss. We may also miss changes that happen too slowly. This is a common problem when observing our environment. Pollution creeps into lakes and streams, fields are eroded, and living things become extinct, all before we realize what’s happening. We humans are adept at ignoring the passage of time. That’s why high-school reunions are so shocking. What a blow to discover that while we haven’t aged, all our classmates have!”

Fig 1.11

Pattern of change

cycles

trends

catastrophes

Fig. 1.12

Fig 1.13

Movement through space — of

discrete point features

linear

areal

volumetric

Break

Representing the Real World

Representing a student in the class

Call for a volunteer ...

PinPoint = 2 310

Low-Res Computer Monitor 640x480 = 307 200

We will refer to this experiment as the lecture unravels

Representing the whole class

List

Name, Student Number, Program, Year

Students as Geographic Features...

Snapshots

with Name (Last, First)

Geographic Data

The issue of data quality

(a bit like cars, drugs, cooking recipe ingredients)

Aspects of information gathering which influence mapped data

the method used to gather data

the way the data are structured

the nature of the quantification achieved

the data inventory scheme

the derivation of statistical summary measures from raw data values

Acquisition Method

Ground Survey

horizontal and vertical measurements

Horizontal measurements

horizontal reference datums (Fig. 2.1)

ellipsoids

Fig. 2.1

Fig. 2.2a

Dead Reckoning

Triangulation

Trilateration

Fig. 2.2

Vertical measurements

elevation

vertical reference datums

mean sea level (MSL)

geoid

geoid-ellipsoid differences (Fig. 2.3)

Fig. 2.3

Global Positioning System (GPS)

Modern survey measurements

Self-Study sub-units:

Census

Remote Sensing

Compilation

Data Model

Object-Oriented Model

(Vector GIS, CAD)

Location Oriented Model

(Grid-based, Raster GIS, cell, pixel, matrix, array, image)

Measurement Level

Table 2.2

Inventory Scheme

Population Counts

errors

instrumental

methodological

human

Spatial Samples

Fig. 2.8

Spatial Prediction

Point to Point Conversions (Figs 2.9 and 2.10)

Interplolation

Extrapolation

Fig 2.9

Fig 2.10

Also discussed are:

Area to Point Conversion (eg. Population Density sample areas)

Area to Area Conversion (eg. Zonal Transformation)

Point to Area Conversion (partitioning space, eg. Fig. 2.15 via Thiessen Polygons, Voronoi Diagrams)