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Advanced Geographic Editing Techniques for Precision Mapping

Explore polygon conversion, coordinate transformations, and raster overlay in GEOG.3530/8535 at University of Nebraska at Omaha. Learn how to merge polygons efficiently and handle complex spatial data with accuracy and repeatability. Dive into coordinate transformations, interpolation methods, and object graphics to enhance your mapping skills.

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Advanced Geographic Editing Techniques for Precision Mapping

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  1. Maps by Computer – Part 2 GEOG 3530/8535 University of Nebraska at Omaha

  2. Slivers

  3. Digitizer x coordinate y coordinate Accuracy: 0.001” Repeatability: 0.003” Impossible to hold hand steady at that degree of resolution.

  4. Arc/Node Topology Arc Begin Node End Node Right Poly Left Poly 1 I II A 0 2 II III B 0 3 III IV C 0 4 V I B 0 5 III V B C 6 IV V D C 7 I IV D A 8 II IV A B

  5. Slivers make polygons Simple Polygon Arc/node Polygon Expected 200 polygons After conversion, we had over 10,000 polygons Solution: Deleted smallest polygons and merged with surrounding polygon. Conversion

  6. Merging Polygons

  7. Redistricting – electoral, congressional

  8. Coordinate Transformations 2x transformation 2,2 becomes 4,4 4,4 becomes 8,8

  9. Rotation u = cos (radang) v = sin (radang) for i = 1, n tempx = x(i) * u + y(i) * v y(i) = -x(i) * v + y(i) * u x(i) = tempx next i

  10. Interpolation What does squaring the distances do? What would the value be if distances cubed?

  11. Object Graphics - Illustrator

  12. Coordinates

  13. Raster Overlay How many commercial/100 year flood pixels?

  14. Overlay

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