Post on 26-Mar-2015
Georeferencing with Paper Maps
Museum of Vertebrate Zoology University of California, Berkeley
& Royal Ontario Museum, Toronto
Overview Map Anatomy
Scale Grid Datum Publisher
Georeferencing with Paper Maps Latitude and Longitude Mathematically Error Calculator
Pros and Cons of Paper Maps
Pros of Paper Maps Necessary for certain localities, such as distances by road and
topographic features, especially when GIS layers are not readily available
Extents more readily obtained Old paper maps may be the only option for obtaining coordinates
for historic localities
Cons of Paper Maps Time-consuming Good quality paper maps may be hard to find Map printing errors
Map of Canada’s Wonderland, N of Toronto, Canada
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Map Anatomy: Map Scale
Map Anatomy: Map Scale
Usually recorded as a ratio, such as 1:100,000, or a fraction, such as 1/100:000
“Large scale” (Fine scale) maps, such as 1/10,000, show finer detail, less area
“Small scale” (Broad scale) maps, such as 1/500,000, show less detail, greater area
Think of “large” & “small” scale as the value of 1 in the fraction. Example 1/10,000 > 1/500,000
Map Anatomy: Map Scale 1:25,000 Large Scale
Map Anatomy: Map Scale 1:250,000Smaller Scale
Map Anatomy: Map Scale 1:500,000
Smaller than before
Map Anatomy: Map Scale 1:1,000,000 Small Scale
smaller than before
Map Anatomy: Grid
Map Anatomy: Grid
Shows the placement of the parallels and meridians on maps
Used to determine latitude and longitude Maps with no grid recorded cannot be used
to determine coordinates – only to determine extents
Map Anatomy: Grid
Map with no grid labeled
Map Anatomy: Datum
Map with no grid labeled
Map Anatomy: Datum
If datum is recorded, usually found near the map scale or publisher’s name
Use Horizontal Datum, not Vertical Occasionally, if no datum is recorded but the
reference ellipsoid is, then one can determine the datum using the pdf document found at http://earth-info.nga.mil/GandG/publications/tr8350.2/wgs84fin.pdf (Use Appendix B)
Determining Coordinates from Paper Maps: Georeferencing Source For Georeferencing Sources be sure to
include the following: Publisher name Map Date Map Scale Map name
Example: United States Geological Society (USGS) Topographic Map California, 1956, map scale 1:24,000, map name “Boone”
Determining Coordinates from Paper Maps
Paper maps are necessary when gazetteers will not report needed coordinates Especially useful for distances by roads and
topographic features like rivers and mountain ranges
Pay special attention to the grid lines and the hemisphere (latitudes in the southern hemisphere are negative, and longitudes in the western hemisphere are negative)
Coordinate Integers for Hemispheres
Determining Coordinates from Paper Maps
Nauru Island, Pacific Islands Geographic Nauru Island, Pacific Islands Geographic
Society, 1960 1:12,000Society, 1960 1:12,000
Determining Coordinates from Paper Maps: Latitude
Determining Coordinates from Paper Maps: Latitude
S
Determining Coordinates from Paper Maps: Longitude
Determining Coordinates from Paper Maps: Longitude
E
Determining Coordinate Precision
Determining Coordinate Precision for the Georeferencing Calculator:Determining Coordinate Precision for the Georeferencing Calculator:
The smallest measurement using our rulers is 1 mm ( = 0.01 cm), The smallest measurement using our rulers is 1 mm ( = 0.01 cm), therefore we need to convert millimeters to minutes:therefore we need to convert millimeters to minutes:
0.1 cm x (2 minutes/14 cm) = 0.014 min0.1 cm x (2 minutes/14 cm) = 0.014 min
Choose the next largest fraction of a minute on the calculator.Choose the next largest fraction of a minute on the calculator.
For 0.014 minutes, select 0.1 minutes.For 0.014 minutes, select 0.1 minutes.
Determining Coordinates from Paper Maps: Error Calculation
In Conclusion Pay attention to whether you should add or
subtract the offsets to the grid points Measure from the center of your feature to the
edge for extent Plot your coordinates to double check your work Explain any decisions you had to make in the
GeoreferenceRemark field Explain any errors in the locality description in
the LocalityErrors field
For Georeferencing Source be sure to include the following: Publisher name Map Date Map Scale Map name
Example: United States Geological Society (USGS) Topographic Map California, 1956, map scale 1:24,000, map name “Boone”
Determining Lat and Long:Determining Lat and Long:
Determining Coordinate Determining Coordinate Precision:Precision:
0.1 cm x (2 minutes/14 cm) = 0.014 min0.1 cm x (2 minutes/14 cm) = 0.014 min
Round up to 0.1 minute precisionRound up to 0.1 minute precision