Information Management
DIG 3563
Spring 2012
Lecture 13: Geographic Data
and Geolocation
J. Michael Moshell
University of Central Florida
Original image* by Moshell et al .
Imagery is fromWikimedia except where marked with *. Licensing is listed.
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Geographic Information
From the Nile River to the GPS Phone
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The World's Coordinate System
Measuring Latitude and Longitude
Surveying: Measuring Land and Water
Geographic Information Systems (GIS)
Global Positioning Systems (GPS and its Sisters)
Google Maps (and its rivals)
Geographically Aware Apps: Augmented Reality
Excerpt from DA Text
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The Grid of the World
Who thought up Latitude and Longitude?
Navigation by choice of a particular star:
Note its position on the horizon; (E or W)
(But what if your destination had no star?)
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The Grid of the World
Who thought up Latitude and Longitude?
Navigation by choice of a particular star:
Note its position on the horizon; (E or W)
(But what if your destination had no star?)
Ancient Sumerians (etc) in Mesopotamia divided the
sky into 360 degrees (the year is "about" 360 days)
because the sun "moves" that far in a day
(with respect to the stars)
wikipedia.org
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The Grid of the World
What are the numbers?
Latitude: 0o = equator, up to +90o North Pole
-45o is in the Southern Hemisphere.
Longitude: 0o = Greenwich; + to the East, - to West
+180o = -180o, in the middle of the Pacific
Traditional units: degrees, minutes, seconds
12o 36' 45"
Modern measurements: decimal degrees: 12.345662
(GPS can do it either way)
wikipedia.org
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The Grid of the World
Who thought up Latitude and Longitude?
Navigation by choice of a particular star:
Note its position on the horizon; (E or W)
(But what if your destination had no star?)
The cross-staff enabled
one to use a star (or sun) to
measure latitude, from
height above horizon
wikipedia.org
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Latitude
What were they measuring?
"How far north or south you are"
45o North: Vermont
wikipedia.org
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Latitude
What were they measuring?
"How far north or south you are"
0o: Equator
wikipedia.org
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Latitude
Convention: North is positive
-45o: Southern Hemisphere
wikipedia.org
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The Grid of the World
Measuring Latitude
Fancier instruments evolved
to measure latitude:
The astrolabe
and
the sextant
wikipedia.org
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The Grid of the World
But East-West (Longitude was MUCH harder)
Key question #1: Why was Longitude harder?
Because the world turns. You are moving eastward at
about 1000 miles per hour.
A star's celestial latitude is constant, but its longitude
changes every minute! So .. what to do?
wikipedia.org
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Dead (Deduced) Reckoning
Compass and Log ("speedometer")
Plot on a map: your compass
heading, your speed.
Extend the line
See where you "should" be
Verify the latitude,
hope the longitude is right.
wikipedia.org
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Finding Longitude
The British established Greenwich Observatory
(outside London) and declared the Prime Meridian
(Laser beam indicating it)
French, Germans, Japanese
didn't agree until 1884.
(Modern methods moved the
prime meridian about 100m west.)
wikipedia.org
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Finding Longitude
The world is divided into 360 degrees of longitude.
If the sun is overhead at Greenwich at 12:00 noon
GMT (Greenwich Mean Time), then
The sun is overhead at (15 degrees west longitude)
at 1:00 PM, GMT
Because 360/24 = 15 degrees
wikipedia.org
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Finding Longitude
So, if you knew "what time is it in Greenwich"
and you observed solar noon at your
location (shortest shadow of a stick)
you could calculate your
latitude.
example: GMT 4 PM is
local noon. 4 hours x 15 deg/hr
=60 degrees. So we are 60
degrees west of Greenwich.
wikipedia.org
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Longitude Disaster
Before radio and good clocks, it was HARD to know
what time it is, somewhere else.
Sir Cloudseley Shovell and the
Scilly Islands Disaster, 1695
wikipedia.org
4 ships, 2000 men lost, due to incorrect longitude
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Longitude Prize
London Navigation Board established
20,000 pound prize.
Many people tried to make
accurate clocks for shipboard
use ("chronometer")
He built H1, H2 and H3 across 30 years
(close, but not perfect)
and watches ..> H4 was actually useful.
wikipedia.org
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Longitude Prize
On a trip from London to
Jamaica, the watch was 5
seconds slow (about 1 nautical
mile)
Lunar Distances was a competing
wikipedia.org
method. When the moon passes
close to a particular star, you can
compute the GMT. But 'lunars' was complex and
vulnerable to weather.
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Chronometers
Captain Cook took K1, a copy
of H4, to the South Seas
The cost of such a chronometer
was about 30% of the cost of the ship!
wikipedia.org
H1 ... H3 are still running at Greenwich.
H4 is stopped as it requires oil (and would degrade)
(I think Harrison is a hero of science..)
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Surveying
When the ancient Nile flooded,
they had to re-measure the
fields. "Geometry" = "measuring
the earth."
wikipedia.org
Romans used a "groma" to establish
E-W and N-S lines for cities
and fields.
(from Greek "gnomon")
surveyhistory.org
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Surveying
Triangulation: The
Principal Triangulation of
Britain
Gunter's
Chain: 66 ft
10 square
chains=acre
(e. g. 2 x 5)
- Useful fields are seldom square -
wikipedia.org
surveyhistory.org
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Surveying
Triangulation: Establish
a baseline by chains
and then extend it by
wikipedia.org
measuring angles
and doing the math (easier than a lot of walking!)
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Aerial Surveying
* Photogrammetry
(stereo pairs of images)
* LIDAR ("Light radar")
- Laser beam time-of-flight
Results: Digital Elevation Model
(array of height values - Z)
Often transformed into a TIN
(Triangulated Irregular Network
list of (X,Y,Z) values
wikipedia.org
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Geographic Information Systems (GIS)
What to do with the data?
Make maps? But paper maps
are VERY labor intensive.
Computers -- > GIS
Can support all kinds of analysis
in addition to drawing maps.
wikipedia.org
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Geographic Information Systems (GIS)
Vector data:
Features –
roads, rivers, houses
contour models (TIN)
Raster data:
wikipedia.org
Imagery –
satellite, aerial, land photos in visible, infrared
Elevation Models
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Layering: An example
Forest: light green
Topography: brown
Stream: blue
Pond: different blue
Boundary: emerald green
Road: black
Structures: Black
wikipedia.org
All of the above except the forest are probably stored
as vector data, often 2d
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The 800 pound Gorilla of GIS
Every State & most counties, cities use ESRI software
for tax maps, land use planning, roads, utilities etc.
ArcInfo  ArcGIS is their premier product line
ArcGIS Explorer Online – a web tool for getting at ArcGIS data.
http://www.esri.com/software/arcgis/explorer-online/index.html
Far more powerful than Google Maps .. but not free!
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Geostatistics
John Snowe (U. K.) First Epidemiologist
Mapped cholera deaths in London.
wikipedia.org
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Geostatistics
John Snowe (U. K.) First Epidemiologist
Mapped cholera deaths in London.
Discovered
a water
pump
at center
of
outbreak
wikipedia.org
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Geostatistics
John Snowe (U. K.) First Epidemiologist
Mapped cholera deaths in London, 1854
Discovered
a water
pump
at center
of
outbreak
wikipedia.org
Removed pump handle,
cholera deaths ceased
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Geostatistics
Radiation spread after
the nuclear accident
at Chernobyl,
Ukrane, 1986
dusk.geo.orst.edu
Heart Attack rates
in the USA,
2000-2004
en.wikipedia.org
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Geocoding
Calculating spatial
coordinates (Lat Long)
from street addresses,
ZIP codes, tax maps,
etc.
Why? For instance, UPS
plans truck routes based on geocoding
to maximize gas mileage for a given
delivery schedule.
wikipedia.org
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Geographic Information Systems (GIS)
Relative Advantages/issues for data formats:
Vector data:
- easy to overlay and analyze
- easy to rescale and match up
Raster data:
- taken at a specific resolution; limited scaling
- usually only one, or a few raster layers
when overlaying layers.
- often transformed to vector (e. g. contours)
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Global Positioning System(s)
Before GPS, how could you find your position?
* benchmarks
* radio direction finding
(navigation)
www.wikipedia.org
www.wikipedia.org
* astronomical navigation (difficult, weather-limited)
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Global Positioning System(s)
Built & operated by US Dept of Defense
Currently 31 satellites
Atomic clocks, time-of-flight
computation
4 satellites must be visible.
Altitude around 12,500 miles
www.wikipedia.org
Originally the accuracy was reduced
for non-Defense applications. Clinton removed this
limitation in 2000. Now
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Global Positioning System(s)
Competitors:
GLONASS (Russian)
GPS was blocked during
South Ossetiawar (2008)
GLONASS fell apart when
Soviet Union collapsed;
yo-mobil, a Russian
(startup) hybrid car,
uses GLONASS navigation
www.wikipedia.org
New version went live in 2010
(restored as Russian economy grew)
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Global Positioning System(s)
Competitors:
GLONASS (Russian)
COMPASS (Chinese)
(Planned)
Galileo (European)
(Planned; 2014)
A GLONASS Satellite
www.wikipedia.org
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Global Positioning System(s)
Relevance to Digital Media:
Location-aware devices are EVERYWHERE now.
Google Maps as an example;
Google Maps API (Javascript)
requires that you specify
if geolocation is available.
www.google.com
This service uses the mobile devices' location system.
(WIFI identification, if no GPS is available.)
(Tower triangulation, if no WIFI is available.)
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Global Positioning System(s)
GPS-via-smartphone vs. GPS-via-specialized device
GPS device has built-in map
database (but how old?)
(And which countries?)
www.garmin.com
GPS phone downloads the
maps (data charge? delay?)
www.zdnet.com
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Google Maps
A Javascript 'toolkit' for building mash-ups
(i. e. producing location-aware websites
of all kinds.)
Your assignment: locate an interesting site that
incorporates Google Maps, and be ready to
"guide a tour" of the site's features.
KEY IDEA: What's EXTRA, other than just markers?
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