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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

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
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

footprinting from the computer s point of view
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
slide4

Four Scenarios of Feature Representation that the Computer Can Understand

Bounding Box

Point

Polygon

Grid

point representation
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

minmax bounding box
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
polygon representation
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

u s national grid
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

how to generate a footprint
How to generate a footprint

Data

GIS data can be run through a

computer program

to generate a footprint.

role of gnis
Role of GNIS

Gazetteer

Digital

Library

National

Map

?

GNIS