Georeferencing

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  • Topic: Universal Transverse Mercator coordinate system, Map projection, Cartography
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  • Published : April 17, 2013
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Review






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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