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Georeferencing with Paper Maps

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.

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Georeferencing with Paper Maps

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  1. Georeferencing with Paper Maps Museum of Vertebrate Zoology University of California, Berkeley & Royal Ontario Museum, Toronto

  2. Overview • Map Anatomy • Scale • Grid • Datum • Publisher • Georeferencing with Paper Maps • Latitude and Longitude Mathematically • Error Calculator

  3. 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

  4. Map of Canada’s Wonderland, N of Toronto, Canada

  5. Map Anatomy: Map Scale

  6. 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

  7. Map Anatomy: Map Scale 1:25,000 Large Scale

  8. Map Anatomy: Map Scale 1:250,000Smaller Scale

  9. Map Anatomy: Map Scale 1:500,000Smaller than before

  10. Map Anatomy: Map Scale 1:1,000,000 Small Scalesmaller than before

  11. Map Anatomy: Grid

  12. 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

  13. Map Anatomy: Grid Map with no grid labeled

  14. Map Anatomy: Datum Map with no grid labeled

  15. 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)

  16. 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”

  17. 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)

  18. Coordinate Integers for Hemispheres

  19. Determining Coordinates from Paper Maps Nauru Island, Pacific Islands Geographic Society, 1960 1:12,000

  20. Determining Coordinates from Paper Maps: Latitude

  21. Determining Coordinates from Paper Maps: Latitude S

  22. Determining Coordinates from Paper Maps: Longitude

  23. Determining Coordinates from Paper Maps: Longitude E

  24. Determining Coordinate Precision Determining Coordinate Precision for the Georeferencing Calculator: The smallest measurement using our rulers is 1 mm ( = 0.01 cm), therefore we need to convert millimeters to minutes: 0.1 cm x (2 minutes/14 cm) = 0.014 min Choose the next largest fraction of a minute on the calculator. For 0.014 minutes, select 0.1 minutes.

  25. Determining Coordinates from Paper Maps: Error Calculation

  26. 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

  27. 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 Coordinate Precision: • 0.1 cm x (2 minutes/14 cm) = 0.014 min • Round up to 0.1 minute precision

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