Crash Course in
Georeferencing
Michelle Koo, Carol Spencer,
Andrew Reagan, Lauren Scheinberg
Good and Bad Locality
Descriptions
Elements and Examples
Overview
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Elements of a Locality
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Verbatim Locality Description
Elevation
Coordinates
Datum
GPS Accuracy
Extent
Reference
Examples
What A Locality Should Be
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Specific
Succinct
Unambiguous
Complete
Accurate
Precise
Less
Precise
Less
Accurate
More
Precise
x
More
Accurate
Locality Tips
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Avoid uncertainty due to imprecise headings
• distance along a path
• two orthogonal distances from a place
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Use only one reference point
• small in size (extent)
• stable in position and size over time
• easy to find on maps or in gazetteers
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Avoid vague terms such as “near”, “vicinity of”,
“about”, etc
Elevation
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Provide an elevation value
Beware elevation from
GPS - it is less accurate
than a barometric altimeter
(when calibrated)
Report the source of
elevation (map, altimeter,
seat of pants, etc.)
Coordinates
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It is not enough to have coordinates alone, a
locality description is essential.
Decimal degrees are recommended. If a
different system is used, record your
resources.
More decimal places are better.
Original coordinates from GPS should be
preserved.
Know your GPS Make/Model and DATUM
Datum
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Datum has a
corresponding
coordinate system
Default datum
WGS84
• Coordinate your
resources, especially if
you’re using a different
datum
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Coordinates without
datum are ambiguous
Be consistent
GPS Accuracy
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GPS accuracy can be
affected by many issues
• number of satellites
• interference
• presence of reflective
surfaces
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Provide the GPS overall
accuracy, or error, while
reading the GPS
coordinates
• It will not be available later,
and are not stored with the
waypoints
Extent
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Indicates the size of the area within which
an event (collection, observation)
occurred
Can be a city, park, intersection, transect,
grid, river, road, etc.
References
Document the sources and tools
 Topographic map in field
 Map title, publisher, scale, year, sheet
number
 Gazetteer or Road Atlas
 Altimeter
 GPS
• Model
• Datum
• Accuracy
Examples of Good and
Bad Localities
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Vague localities
• BAD: “Sacramento River Delta” - an extremely
large geographic area
BETTER: “Locke, Sacramento River Delta,
Sacramento Co., California” - names a town
within the Delta
• BAD: “3 mi W of San Jose/Cartago border” without additional details, this would mean
anywhere 3 mi W of the border
GOOD: “3 mi W of San Jose/Cartago border on
Highway 2, San Jose Province, Costa Rica”
Examples of Good and
Bad Localities
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Names of Roads without additional
reference
• BAD: “Highway 9, Alajuela Province, Costa
Rica”
GOOD: “Intersection of Hwy 9 and Rio
Cariblanco, Cariblanco (town), Alajuela
Province, Costa Rica”
• BAD: “S Berkeley, Alameda County, California”
GOOD: “Oakland,1 mi S of intersection of 66th
St and Telegraph Ave on Telegraph Ave.,
Alameda Co., California”
Examples of Good and
Bad Localities
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Localities that are difficult to
Georeference
• BAD: “Battle Mountain, Lander Co.,
Nevada”
BETTER: “Battle Mountain (city), Lander
Co., Nevada”
• BAD: “Km 58 Pan American Highway”
GOOD: “Km 58 Pan American Highway, 6
km S of Cartago on Pan American
Highway, Cartago Province, Costa Rica”
REAL LOCALITIES FROM MaNIS
Vague
Biologically unlikely
Non-sensical
Requires specific knowledge
Online Resources
Locality Guidelines
http://mvz.berkeley.edu/Policies.html
http://mvz.berkeley.edu/Locality_Documentation.html
Online resources for georeferencing
http://herpnet.org/Gazetteer/GeorefResources.htm
Online resources for georeferencing
http://canadensys.net/digitization/georeferencing
Google Maps
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http://maps.google.com
Search & directions
• Free text search,
zoom -dependent
• Directions for travelling by car, bike, public transport and
foot
• Data compiled from different sources
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Maps
• Datum: WGS84
• Views: map, satellite (= aerial photography), terrain,
Google Street View + various layers of information
• Data compiled from different sources (indicated at the
bottom of each map)
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Third Party Plug-ins extend functionality
Google Maps - Searching
Search now with suggestions
Google Maps - Viewing
Maps
Terrain (under ‘More’)
Satellite
Earth (plug-in required)
Google Maps – Street View
Street View
Google Maps – Street View
I collected here
Google Maps – Getting coordinates
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Requires additional widgets or plug-ins
• Activate LatLng Marker in Google Maps Labs
• Install a mapplet like GPS Location or Position
Finder in ‘My Maps > Browse the directory’. Now
deprecated!
• Use Canadensys LatLong Crosshairs bookmarklet:
http://www.canadensys.net/georeferencing
Use Distance Measurement Tool to measure extent
Use My Maps to save markers, create maps, share
with others (including kml import)
Google Maps – Getting coordinates
Google Maps Labs
LatLng Marker
Right-click and‘Drop LatLng Marker’
(activate in ‘Labs’ first)
Google Maps – Getting coordinates
Canadensys bookmarklet
Click to toggle
Crosshairs
Pan map to change position
Click to get coordinates
Google Maps – Measuring extent
Distance Measurement Tool
(activate in ‘Labs’ first)
Google Earth
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http://earth.google.com
3D globe desktop application
Same data as Google Maps
• Datum: WGS84
• No Map or Terrain view
Similar functionalities as Google Maps
• Search more limited than Google Maps (no suggestions)
• Right-click and choose ‘Get Info’ for coordinates
• Use ruler to measure extent
• Several coordinate formats
• Numerous information layers (format: kml)
AcmeMapper
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http://mapper.acme.com/
Google Maps interface
• Datum: WGS84 (& NAD27)
• Map, satellite, hybrid and terrain
• Topo, DOQ, NEXRAD and Mapnik
• Free text search not Zoom level-dependent
• Markers cannot be moved, but new markers can be
placed at crosshairs (click ‘Mark’)
• Several coordinate formats for each marker +
heading and distance from crosshairs
• Saves all markers automatically
GEOnet Names Server (GNS)
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http://earth-info.nga.mil/gns/html/
Worldwide data from NGA and
US BGN
• NIMA = National Imagery and
Mapping Agency
• Datum: WGS84
• Degrees minutes seconds,
precision to nearest minute
• Feature type
• Used as a source for many gazetteers
For US data, use Geographic Names Information System
(GNIS): http://geonames.usgs.gov/pls/gnispublic/
Geographical Name Search Service (GNSS)
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http://gnss.nrcan.gc.ca/gnss-srt/searchName.jsp
Canadian data by the Canadian
Geographical Names Service
(CGNS)
• Datum: NAD83
• Degrees minutes seconds and
decimal degrees
• Feature type
Full Canadian Geographical Names datasets can be
downloaded from GeoBase: http://www.geobase.ca/
Falling Rain
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http://www.fallingrain.com
Worldwide gazetteer for cities
and towns
Great for hard to find localities,
especially outside US
• Datum: WGS84
• Degrees minutes (seconds), based on NIMA
• Browse to find locality (no search)
• Provides hierarchy, alternative names, topo maps, altitude,
weather information and location of nearby towns in
nautical miles (nm).
Tip: Use Google/Chromey to translate nm into km.
Example: Qaryeh-ye Gol`alam, Velayat-e Lowgar, AF
You can also check against Statoids: http://www.statoids.com/
Getty Thesaurus of Geographic Names (TGN)
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http://www.getty.edu/research/conducting_research/vocabular
ies/tgn/
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Worldwide gazetteer by
The Getty
Useful for finding alternative
and old names
• Feature types
• Geographical hierarchy
• Coordinates only to minutes (or not at all)! Use recent
name and search in Google Maps
Example: Big Apple, inhabited place, United States
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FuzzyG – JRC Fuzzy Gazetteer
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http://dma.jrc.it/services/fuzzyg/
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Worldwide gazetteer
designed for bad spelling!
Useful for finding alternative,
doubtful spelling, old names
• Feature types
• By continent
• Coordinates only to minutes (or not at all)! Use recent
name and search in Google Maps
Example: Narobi, Africa
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Other Resources
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GPS Visualizer: http://www.gpsvisualizer.com/
• Use to translate a file with coordinates into kml or a picture
• Similar: http://www.simplemappr.net/ for publications
GeoLocate: http://www.museum.tulane.edu/geolocate/
• Georeferencing desktop and web application
• Useful for roads and rivers (US only)
Statoids: http://www.statoids.com/
• Information about administrative divisions (provinces,
counties) and their history, area, population, codes, etc.
• No coordinates!
• Similar: CIA World Factbook http://bit.ly/dDtT1i
See http://herpnet.org for more…
BioGeomancer:
Semi-automated
Georeferencing Engine
http://bg.berkeley.edu/latest/
Currently works on Firefox, Explorer,
not Chrome, Safari.
Developed by: John Wieczorek, Aaron Steele, Dave Neufeld, P.
Bryan Heidorn, Robert Guralnick, Reed Beaman, Chris Frazier,
Paul Flemons, Nelson Rios, Greg Hill, Youjun Guo
37 Locality Types
F – feature
 P – path
 FO – offset from a feature, sans heading
 FOH – offset from feature at a heading
 FO+ – orthogonal offsets from a feature
 FPOH – offset at a heading from a feature
along a path
 31 other locality types known so far
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Five Most Common Locality Types*
51.0% - feature
 21.4% - locality not recorded
 17.6% - offset from feature at a heading
 8.6% - path
 5.8% - undefined
 types of localities BG recognizes
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*based on 500 records randomly selected from the 296k
records georeferenced manually in the MaNIS Project.
Types of Data BG Uses and
Georeferences
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BG has >11 million entries in the gazetteer
http://www.biogeomancer.org/metadata.html
User created places = 112,000
1.5 million localities were georeferenced,
for 6.2 million georeferences (so on average 4
georeferences per locality)
Over 500 login users, 6,000 projects done
ORNIS did 189k localities in BG batch processing
How BG works:
Additional BG Commands:
•Add: lets you add another georeference to the current
view
•Hg: searches on higher geography only
•Create: lets you create a new locality (this only works
if you are not logged in)
•Also you can display lat and longs by typing
coordinates into the georeference box, with a space
between them (no comma)
•http://bg.berkeley.edu/latest/
Batch Processing:
https://sites.google.com/site/biogeom
ancerworkbench/support/batch-
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Georeferencing tool originally
designed for aquatic natural history
data
Calculates Uncertainty in same
standards
Several Versions: standalone
desktop, web app, java client app (in
development), web services
Online Exercises
Download exercise and all handouts
here:
http://mvzgis.wordpress.com/tutorials
/shortgeorefws/
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