# Georeferencing

**Topics:**Universal Transverse Mercator coordinate system, Map projection, Cartography

**Pages:**18 (2014 words)

**Published:**April 17, 2013

4 Types of data in GIS: spatial, attribute,

temporal, and metadata.

Last week we covered attribute data

Today, we will cover spatial data—specifically

georeferencing, map projections and

coordinate systems, and geocoding.

Next topic Geographic Representation &

Vector Data Model

Lecture 03: Georeferencing

GIS6100

Downs

1. Spatial Information

1. Spatial Information

3 main categories

References

Properties

Relationships

1. Spatial Information

a. References—define where things, events,

and activities are located

1. Spatial Information

a. References—examples

Coordinate systems

1. Spatial Information

a. References—examples

Place names

Monument Square

1. Spatial Information

a. References—examples

Addresses

1. Spatial Information

a. References—examples

Linear locators

1. Spatial Information

b. Properties—‘spatial attributes’

1. Spatial Information

b. Properties

Length

1. Spatial Information

b. Properties

Area

1. Spatial Information

b. Properties

Shape

1. Spatial Information

b. Properties

Center

Calculate these

next week

1. Spatial Information

c. Relationships—define associations

between entities

1. Spatial Information

c. Relationships—examples

Connectivity

1. Spatial Information

c. Relationships—examples

Adjacency

B

A

1. Spatial Information

c. Relationships—examples

Co-location (overlap, intersect, etc)

(cover properties and

relationships in detail

later in course)

2. Georeferencing Systems

2. Georeferencing Systems

a. Define how locations of things, events, and

activities are recorded

2. Georeferencing Systems

b. Properties

2. Georeferencing Systems

b. Properties

i. Unique, at least within some domain

Newcastle, Indiana, USA

Newcastle, England, UK

2. Georeferencing Systems

b. Properties

ii. Persistent through time

2. Georeferencing Systems

b. Properties

iii. Have an associated spatial resolution

‘Istanbul’ is

more precise

than ‘Turkey’

2. Georeferencing Systems

b. Properties

iv. Can be metric (compute distances

mathematically) or non-metric

3. Geographic Coordinate System

(GCS) of Earth

--our most important georeferencing system

3. Geographic Coordinate System

(GCS) of Earth

a. Network of latitudes and longitudes to uniquely

identify point locations

3. Geographic Coordinate System

(GCS) of Earth

b. ± φ , ± λ (phi, lambda); see Fig 2.6, 2.7

3. Geographic Coordinate System

(GCS) of Earth

b. (± φ , ± λ); (phi, lambda); see Fig 2.6, 2.7

(3.f.) Examples

Tampa (S)

27° 58' N 82° 32' W

Istanbul (Turkey) 40° 58' N 28° 50' E

Santiago (Chile) 33° 27' S 70° 42' W

Lima (Peru)

12° 5' S

77° 3' W

Tokyo

35° 41' N 139° 46' E

Petropavlovsk 52° 53' N 158° 42' E

*can either specify N/S, E/W or make W and S

negative

3. Geographic Coordinate System

(GCS) of Earth

c. Meridian: a line of constant longitude

(e.g. Prime Meridian)

3. Geographic Coordinate System

(GCS) of Earth

d. Parallel: a line of constant latitude

(e.g. Equator)

3. Geographic Coordinate System

(GCS) of Earth

e. Can be recorded in degrees (minutes,

seconds) or decimal degrees

e.g. 60º 30’ 0” or 60.5º

also, when used in GIS, the data are ‘unprojected’,

so spatial calculations cannot be computed (e.g.

area) and scale bar cannot be shown correctly;

why?

4. Map Projections

4. Map Projections

—transform 3D Earth surface onto 2D map

surface

4. Map Projections

a. Causes distortion errors—tearing,

shearing, compression—which alter area,

shape, distance, and/or direction

measurements

4. Map Projections

b. Particular map projections attempt to

‘preserve’ one or more of these properties

4. Map Projections

b. Particular map projections attempt to

‘preserve’ one or more of these properties

4. Map Projections

b. Particular map projections attempt to

‘preserve’ one or more of these properties

i....

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