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GNIS Footprints in an Internet GIS

GNIS Footprints in an Internet GIS. Gathering GNIS Footprints for Polygon Areas Georgianna Strode Florida State University Florida Resources and Environmental Analysis Center (FREAC). What is a footprint?.

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GNIS Footprints in an Internet GIS

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  1. GNIS Footprints in an Internet GIS Gathering GNIS Footprints for Polygon Areas Georgianna Strode Florida State University Florida Resources and Environmental Analysis Center (FREAC)

  2. What is a footprint? • A footprint is an approximation, expressed in latitude/longitude coordinates, of the subset of the Earth's surface occupied by the place. • Can be used for purpose of analysis Footprints of Place Names Of Rivers List of Rivers “in” Philadelphia Mapping/ GIS Footprint of Philadelphia Footprints of Water Reports List of Water Reports concerning Lake Talquin Footprint of Lake Talquin Digital Library

  3. Footprinting from the Computer’s Point of View • Policy makers can use broad footprinting definition • Computer / map needs more specifics information. Footprint definition needs to be expanded to include coordinates • Purpose of this presentation is to show four footprinting scenarios that computer / map can understand

  4. Four Scenarios of Feature Representation that the Computer Can Understand Bounding Box Point Polygon Grid

  5. Point Representation Data Pro Map Con • Does not show feature size nor shape • Map users must be educated to understand implications of point data • Not good for analysis • This is the current GNIS standard • Easy to understand • Easy to work with • Works well for locating features on map (see LABINS for an example) Lat Lon Sample ofGNISData

  6. MinMax Bounding Box • Does not show true size nor shape of the feature • Irregularly shaped features may be misrepresented Map Data Pros Cons Min X Min Y Max X Max Y • Easy to understand • Easy to work with

  7. Polygon Representation • Computer processing may be more complicated than other scenarios • Too-detailed boundaries can increase processing efforts • Implied accuracy is likely false (whose interpretation is correct?) (what happens over time?) • Users could mistake the footprint for the real thing Map Data Pros Cons Lat Lon Lat Lon Lat Lon Lat Lon Lat Lon . . . Lat Lon • Map shows full shape and size of feature • Easy to understand Interpretations True Coordinates OK Hand-drawn footprints OK Mathematical Formulas OK

  8. U.S. National Grid • Not easy to understand, but this could possibly be corrected through an educational program Map Data Pros Cons • Can show reasonable size and shape of feature • Can vary grid size or “resolution” as needed R17US400600 R17EA456998 R17US400600 R17EA456998 R17US400600 R17EA456998 R17US400600 R17EA456998 … R17US9934 Variable Grid Size 0 digits = 100,000 meters 2 digits = 10,000 meters 4 digits = 1,000 meters (neighborhood) 6 digits = 100 meters (soccer field) 8 digits = 10 meters (modest home) 10 digits = 1 meter (parking lot) Interpretations U.S. National Grid OK Variable-sized cells OK Homemade Grids OK

  9. How to generate a footprint Data GIS data can be run through a computer program to generate a footprint.

  10. Role of GNIS Gazetteer Digital Library National Map ? GNIS

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