The document describes how researchers mapped the trip patterns of persons with disabilities using GPS data. They collected location data every 5 seconds from GPS devices and obtained tables with over 100,000 data points for each person. The researcher then explored different ways of visualizing the data, such as point maps, line maps showing trips, and maps color-coded by speed. They found that visualizing only parts of the data or calculating point densities helped reveal patterns. Considering factors like data inaccuracies inside buildings, they were able to create maps that served the purpose of understanding how persons with disabilities move in urban areas.

1. Alireza Karduni
How Thinking About Data
Affects Mapping!
(Cartography!)

2. A Story!
• Every mapping has a purpose!
• The purpose is to communicate!
• Communicate information!
• Geographical, Social, Population, …

3. A Story!
• We wanted to map how persons with disability move in urban areas.
• We wanted to map their TRIP PATTERNS (Trips, Destinations, home,
work, etc)
• So we gave a number of them GPS devices
• The device recorded their location every 5 seconds.
• After a while, We got the device back

4. A story!!
• This is what we got back.

5. A story!!
• This is what we got back.
• Tables with more that 100,000 GPS points for each person
• With :
• Coordinates (location)
• Speed
• Headings (direction)
• Date
• Time ( when the data was recorded)

6. A story!!
• Now using only this data we want to make meaningful maps that
serve our purpose.

7. Location!
• We used Lat/Long
information to make a point
map of all GPS data!

8. Base Map!
• We projected the data to be
able to use the base
imagery!
• Imagery is a kind of data:
• We can change the tone and
color to make the map more
legible

9. Base Map!
• Imagery is a kind of data:
• We can change the tone and
color to make the map more
legible
• Did it serve our purpose
well?
• Not really!

10. Part of the data
• Looking at parts of the data
makes it easier to see
patterns in the subjects trip.
• Now we can almost see the
difference between his trips
and destinations

11. Size!
• Does the point sizes matter?
• Yes it does !
• Does it make my map serve
my purpose better ?
• I guess not!

12. Two points make a line
• We can make lines out of
our points.
• Is it better?
• Trips ?
• Destinations ?

13. Two points make a line
• Line Thickness makes a
difference
• Same questions should be
asked everytime!

14. Two points make a line
• Line Thickness makes a
difference
• Same questions should be
asked everytime!

15. Back to points
• Back to points

16. Back to points
• We can calculate point
density using each points
location.

17. Back to points
• What does it mean?

18. Speed?
• Make a map that colors the
point based on the speed.

19. Speed?
• What does it mean?
• Inaccuracy always exists!
• Keep that in mind!

20. • The locations are not
accurate
• Can we use this fact for our
purpose?
• Yes!
Inaccuracy?

21. Headings!
• We have the direction for
each point
• We can map it!
• But data is inaccurate!

22. Headings!
• When the subject goes
inside a buildings the point
go crazy
• The headings get really
inaccurate!
• Can we use that to our own
benefit?

23. Headings!
• When the subject goes
inside a buildings the point
go crazy
• The headings get really
inaccurate!
• Can we use that to our own
benefit?

24. Headings!
• We put the headings in 8
different categories
• N , NW , E , NE , ….
• Then counted how many
different categories were in a
150 feet radius around each
point
• If there is 8 different categories
! It means it is a inaccurate
• when does it get in accurate?

25. Headings!
• What does it mean?

26. Think about your data
• After thinking about different ways to think about the data,
• And how to present them
• And what their meaning is
• We can decide which one serves our purpose better

27. DATA!
•The best map is not always
the easiest map to make!
•The best map is not always
the most complicated map!

28. Thanks!