The project proposal involves analyzing data from a consumer survey on seafood preferences conducted in 2021. The survey included online and in-person components, with the online survey gathering location coordinates. The in-person survey was only conducted in Maine and did not collect coordinates but did collect addresses that will be geocoded. The data will be used to assess consumer preferences for aquaculture and wild seafood across the coastal United States.

1. Project Proposal Due 9/21
One or two paragraphs describing what you
would like to accomplish.
A description of the data you think you will
need, and whether or not you have access
to the data, or will you need to find it or
create it?
Lecture 4 1

2. Example 1
• My project proposal involves data from a
consumer experiment I performed last
year. The experiment looks to assess
consumer preferences for aquaculture and
wild harvested seafood products.
Lecture 4 2

3. • The survey was broken up into two
components: online and in-person. The
online participants have coordinates in
decimal degrees linked to their results.
The coordinates show the location from
where the survey was taken. This would
help me to determine if I gathered a
representative sample of the coastal
United States. The sample size is slightly
above 2,000.
Lecture 4 3

4. • In addition, there was an in-person aspect
of the survey that did not gather
coordinate information from the
participants, whom all reside in Maine.
However, I have the addresses of the
participants and plan to geocode their
addresses in order to see where people
came from in order to take our survey.
Lecture 4 4

5. Example 2
• In 2005, The city of New Orleans was hit
by one of the deadliest hurricanes(Katrina)
in American history. The home of Jazz
music was left in shambles as the storm
wreaked havoc- leaving behind many
dead and a great portion of the city
damaged. The perils of hurricane Katrina
are still visible as I experienced this
firsthand during a service trip to New
Orleans in February.
Lecture 4 5

6. • Some of the locals where I served shared
with me how difficult it was to evacuate
from deeply affected areas to places of
safety. This left me sad, but also motivated
to do something. This project gives partner
and I an opportunity to do something.
Lecture 4 6

7. • Together, will be studying the coastland
wetlands in New Orleans to identify the
areas that’re most likely to be affected by
a hurricane or flood event. We will then
design an evacuation plan around the city
of New Orleans. The identification of the
areas with the highest threat along with
the evacuation plan will be done &
displayed in Arc Map. Our next step will be
to use 3D maps as well as simple maps to
display the evacuation plan.
Lecture 4 7

8. Ch. 3 Problems
3.5 Provide three reasons why there have
been various estimates for the Earth’s
ellipsoidal radii.
3.6 Define the geoid. Tell how it differs from
the ellipsoid, and from the surface of the
Earth. Describe how we measure the position
of the geoid.
3.7 Define a parallel or meridian in a
geographic system. Describe where the zero
line occurs.
Lecture 4 8

9. 3.9 Define a datum. Describe how datums
are developed.
3.10 Why are there multiple datums , even
for the same place on Earth. Define what
we mean when we say datum shift.
3.22 What is a developable surface. What
are the most common shapes for a
developable surface?
3.28 Define and describe the UTM
coordinate system.
Lecture 4 9

10. What type of developable surface is used
with the a UTM projection. What are UTM
zones, where is the origin of a zone, and
how are negative coordinates avoided?
3.29 What is a datum transformation? How
does it differ from a map projection?
Lecture 4 10

11. Lecture 4 11
Maps & Data Entry
Chapter 4 – pp 147-170

12. Spatial Data
• Hard Copy –drawn, written or printed
documents, including survey
measurements and legal documents.
• Digital data – are in computer compatible
form
– A considerable amount of digital data has
been converted from hardcopy sources.
– Today a lot of digital data is also collected
digitally.
Lecture 4 12

13. Lecture 4 13
Analogue vs. Digital Data
• Analogue (hardcopy)
– Paper maps
– Tables of statistics
– Hard copy aerial photographs
• Digital data is already in computer readable
format and can come from a variety of sources:
– The internet
– Digital imagery
– Data collection devices
• If data were all in the same format, type, scale
and resolution, encoding would be simple.

14. Lecture 4 14

15. Lecture 4 15
Graticule
Lines of lat/long
Grid
Lines of constant
coordinates

16. Images
Lecture 4 16
Images can provide the backdrop for a map.

17. Lecture 4 17
Images

18. Lecture 4 18
3-D

19. Lecture 4 19
Types of Maps
• There are many different types of maps.
The four most common are:
– Feature maps are the simplest as they map
points lines or areas.
– Choropleth maps depict quantitative
information for areas.
– Dot-density maps also depict quantitative
information.
– Isopleth maps/contour maps display lines of
equal value.

20. Lecture 4 20
Feature Map

21. Lecture 4 21
Choropleth Unique Value

22. Lecture 4 22
Choropleth
Graduated Color Maps
The most
important
assumption in
choropleth
mapping is
that the value
in the
enumeration
unit is spread
uniformly
throughout the
unit.
http://www.pbcgis.com/normalize/

23. Lecture 4 23
Graduated Color Maps
• It is traditional to use
ratios instead of total
values when creating
graduated color maps.
• Most mapping areas
are unequal. The
varying sizes and their
values will alter the
impression of the
distribution.

24. Lecture 4 24
Proportional and Graduated
Symbol Maps
• Guidelines
– Circles are the most common symbol used due to
the ease with which they are interpreted.
– All symbols should generally be the same color.
– The difference between the largest and smallest
symbols should be great enough to show
differences in data values.
– Largest symbols should not overlap so much that
they obscure patterns on the map.

25. Lecture 4 25
Proportional and
Graduated Symbol Maps
• What are they?
– Proportional Symbol
• The size of a point
symbol varies from
place to place in
proportion to the
quantity that it
represents.
– Graduated Symbol
• Size of a point symbol
is based on which
class the features
value falls within.

26. Lecture 4 26
Dot Density Maps
• What are
they?
– Dot density
maps use a
dot to indicate
one or more
occurrences
of a
phenomena.

27. Lecture 4 27
Dot Density Maps
Select a dot
value that is
easily understood
such as 5, 100,
1000, etc.
Choose a dot value
that results in two
or three dots
being placed in
the area with the
least mapped
quantity.
The dots should coalesce in the
statistical area that has the highest
density of the mapped value.

28. Lecture 4 28
Dot Density Maps
• Advantages
– Easily understood
by the reader
– Illustrates spatial
density
– Original data can
be recovered from
the map if the dots
represent the
actual locations of
the phenomena 1 dot = 5 births
Therefore 6 dots =
30 births

29. Lecture 4 29
Dot Density Maps
• Disadvantages
– A dot map that is
computer
generated typically
involves a random
distribution of dots
within an
enumeration area.
– Solution - Use
census blocks over
tracts, counties
over states, etc.
Population
1 dot = 5000 persons
Population
1 dot = 5000 persons

30. Lecture 4 30
Isopleth Maps
• Isopleth maps are used to visualize
phenomena that are conceptualized as
fields, and measured on an interval or ratio
scale.
• We can, however, also color them in such
a way as to represent ordinal and nominal
data as well.

31. Lecture 4 31
http://enb110-ert-2012.blogspot.com/2012/08/maps-chloropleth-map-is-used-as-way-to.html

32. Lecture 4 32
Chart

33. Lecture 4 33
Result of a T-
test performed
to identify areas
of significant
change in deer
harvest.
Statistical Analysis

34. Lecture 4 34
•The amount of reduction that takes place
in going from real-world dimensions to the
new mapped area on the map plane.
•Map scale is unambiguous on hardcopy
maps, but a fixed scale makes no sense
on a digital document when you can zoom
in and out.
•Types of map scales: verbal vs bar
Map Scale

35. Lecture 4 35
One foot equals 24000 feet
One inch equals one mile
•Useful for a quick sense of ground
units in familiar units.
•Unreliable, subject to
misinterpretation, invalidated by
reduction and enlargement.
Verbal Scales

36. Lecture 4 36
•Most effective
•Map user can better measure and
interpret distances within the map area.
•Expands or shrinks along with other
map distances, so it remains valid over
all reductions and enlargements.
Bar Scales

37. Lecture 4 37
Map Generalization
• Maps are abstractions of reality.
• This abstraction introduces map
generalization, the approximation of
features.

38. Lecture 4 38
Penobscot Bay at Different Scales
and Different Generalizations

39. Lecture 4 39
Types of Map Generalization
Road
Grouped
Omitted
Road
Truth
Road
Road
Offset
Exaggerated
True Scale Road Width
Standard Symbol Road Width
Categorized
fen
water
water
fen
fen
swamp
water
marsh

40. Lecture 4 40
Map Boundaries
• Hard copy maps have edges, and discontinuities
often occur at edges.
• Most digital maps have been digitized from
hardcopy maps so edge discontinuities have
been carried into the present.
• These errors are being corrected as newer data
are being collected by digital means.
• Differences in time of data collection for different
map sheets can also cause errors at the edges.

41. Spatial Data Input from
Hardcopy Sources
Lecture 4 41
Common Input Methods:
keyboard entry
manual digitizing
automatic digitizing
scanning
format conversion

42. Lecture 4 42
Data Encoding
• The process of getting data into the computer.
• Spatial data
– Different sources
– Different formats
– Input via different methods
• As a result, GIS data must be corrected or
manipulated to be sure they can be structured
according to the desired data model.

43. Lecture 4 43
Problems to Be Addressed
• Reformatting
• Reprojection
• Generalization of complex data
• Edge matching of adjacent map sheets

44. Lecture 4 44
Figure 5.1 The process of data encoding may be referred to as the data stream
Heywood, Cornelius & Carver – Geographical Information Systems (4th Ed.)

45. Lecture 4 45
Tabular Data
• Attribute data
• Spatial data
– Coordinate data
• Add x,y data – it comes in as an event theme
• Export to shapefile or feature class
– Address data (requires a road file)
• Geocoding converts addresses to x,y data

46. Lecture 4 46
Geocoding
• Geocoding is the
process of finding
associated
geographic
coordinates (often
expressed as lat/long)
from other geographic
data.
• Address matching is
the most common
form of geocoding.

47. Lecture 4 47
Applications of Geocoding
• Internet Services: Google, Yahoo,
Mapquest
• Business: market/area analysis, real
estate
• Emergency Services
• Crime Analysis
• Public Health Services

48. Lecture 4 48
Manual Digitizing
Tracing the location
of “important”
coordinates
Done from an image
or map source

49. Lecture 4 49
Manual Digitization – Map
Digitization
Digitizing Tablet
On-screen Digitizing/
Heads-up Digitizing

50. Lecture 4 50
Manual Digitizing Process
from hardcopy map:
1. Fix map to digitizer table
2. Digitize control points (tics,
reference points, etc.) of
known location
3. Digitize feature boundaries
in stream or point mode.
4. Proof, edit linework
5. Transform or register to
known system (may also be
done at start)
6. Re-edit, as necessary
Accuracies of between 0.01
and 0.001 inches

51. Lecture 4 51
#
Y
#
Y
#
Y
#
Y #
Y
#
Y
#
Y
#
Y
#
Y
#
Y
#
Y
#
Y
#
Y
1
2
3
4 5
6
7
8
9
10
11
12
13
A well-distributed, precisely identifiable set of control points

52. Lecture 4 52

53. Lecture 4 53
Figure 5.4 Point and stream mode digitizing (Heywood, Cornelius & Carver)

54. Lecture 4 54
Digitize Primarily from Cartometric Maps
Based on
coordinate
surveys
Plotted and
printed
carefully

55. Lecture 4 55
Manual Map Digitization, Pros and Cons
Advantages
•low cost
•poor quality maps (much editing, interpretation)
•short training intervals
•ease in frequent quality testing
•device ubiquity
Disdvantages
•upper limit on precision
•poor quality maps (much editing, interpretation)
•short training intervals
•ease in frequent quality testing
•device ubiquity

56. Lecture 4 56
DATA SOURCES, INPUT, AND OUTPUT
Problems with source maps:
Dimensional stability (shrink, swell, folds)
Boundary or tiling problems
Maps are abstractions of Reality
Features are generalized:
•classified (e.g., not all wetlands are alike)
•simplified (lakes, streams, and towns in a scale
example)
•moved (offsets in plotting)
•exaggerated (buildings, line roadwidths, etc).

57. Lecture 4 57
Figure 5.13 Examples of spatial error in vector data (Heywood, Cornelius and Carver)
Manual Digitizing
common errors that require editing

58. Lecture 4 58
Digitizing Accuracy

59. Lecture 4 59
Editing
Manual editing:
Line and point locations are adjusted on a graphic
display, pointing and clicking with a mouse or
keyboard. Most controlled, most time-consuming .
Interactive rubbersheeting:
Anchor points are selected, again on the graphics
screen, and other points selected and dragged
around the screen. All lines and points except the
anchor points are interactively adjusted.

60. Lecture 4 60
Figure 5.20 Rubber sheeting (Heywood, Cornelius & Carver)

61. Lecture 4 61
Figure 5.15 Radius topology feature snapping (Heywood, Cornelius and Carver)
Source: 1Spatial. Copyright © 2005 1Spatial Group Limited. All rights reserved

62. Lecture 4 62
Snapping Errors

63. Lecture 4 63
Manual Digitizing – Vertex Density
Use a spline
interpolation
Use line thinning

64. Lecture 4 64
Figure 5.18 The results of repeated line thinning (Heywood, Cornelius and Carver)
Sources: (a–f): From The Digital Chart of the World. Courtesy of Esri. Copyright © Esri. All rights reserved; (inset): From Esri, ArcGIS online help system, courtesty of Esri. Copyright © 2011
Esri. All rights reserved

65. Lecture 4 65
Common problem:
Features which occur on
several different maps
rarely have the same
position on each map
What to do?
1. Re-drafting the data
from conflicting sources
onto the same base map,
or
2. Establish a "master"
boundary, and redraft
map or copy after
digitizing

66. Lecture 4 66
Digitizing Maps - Automated Scanners
•Main alternative to manual digitizing for hardcopy
maps
•Range of scanner qualities, geometric fidelity
should be verified
•Most maps are now available digitally – however
many began life as paper maps

67. Lecture 4 67
Figure 5.7 Types of scanner
Sources: (a) Epson (UK) Ltd used by permission; (b) Stefan Kuhn, www.webkuehn.de; (c) Colortrac, www.colortrac.com
(Heywood, Cornelius and Carver)

68. Lecture 4 68
Practical Problems of Scanning
• Optical distortion from flatbed scanners.
• Unwanted scanning of handwritten
information.
• The selection of appropriate scanning
tolerances.
• The format of files produced for GIS input
• The amount of editing required to produce
data suitable for analysis.

69. Lecture 4 69

70. Lecture 4 70
Digitizing Maps - Automated Scanners
•Suitable threshholding allows determination of
line or point features from the hardcopy map.
•Scanners work best when very clean map
materials are available.
•Significant editing still required (thinning,
removing unwanted features)

71. Lecture 4 71
Cell Thinning and Vectorizing– After Scan-Digitizing

72. Lecture 4 72
Georeferencing
• In order to display images with coverages
or shapefiles, it is necessary to establish
an image-to-world transformation that
converts the image coordinates to real-
world coordinates. This transformation
information is typically stored with the
image.

73. Lecture 4 73

74. Lecture 4 74

75. Lecture 4 75

76. Lecture 4 76

77. Lecture 4 77
Rectified Image
• GeoTiff - store the georeferencing information in
the header of the image file. ArcView uses this
information if it is present.
• World Files - However, other image formats
store this information in a separate ASCII file.
This file is generally referred to as the world file,
since it contains the real-world transformation
information used by the image. World files can
be created with any editor.

78. Lecture 4 78
World Files
• It’s easy to identify the world file which
should accompany an image file: world
files use the same name as the image,
with a "w" appended. For example, the
world file for the image file mytown.tiff
would be called mytown.tiffw or
mytown.wtf

79. Lecture 4 79
The Contents of the World File
20.17541308822119 (x-scale factor)
0.00000000000000 (rotation)
0.00000000000000 (rotation)
-20.17541308822119 (y-scale factor)
424178.11472601280548 (x-translation)
4313415.90726399607956 (y-translation)
• When this file is present, ArcView performs the
image-to-world transformation.

80. Assignment
• Read Ch. 4 to page 170
• Try problems: 1, 3, 4, 9 12
Lecture 4 80