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Map-Making with the NHD

Map-Making with the NHD. Bill Wheaton Research Triangle Institute wdw@rti.org, (919) 541-6158. Mapmaking with the NHD. Topics Map Design and Layout Using NHD Content in Maps Displaying Other Data with NHD. Map Design and Layout.

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Map-Making with the NHD

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  1. Map-Making with the NHD Bill Wheaton Research Triangle Institute wdw@rti.org, (919) 541-6158

  2. Mapmaking with the NHD • Topics • Map Design and Layout • Using NHD Content in Maps • Displaying Other Data with NHD

  3. Map Design and Layout • Modern Tools Don’t Alleviate the Need for Proper Map Design and Layout • Who is the audience? • What is the map communicating? • What are the uses for the map? • Colors, projections, use of white space, etc.

  4. Feature Issues • What are the NHD Feature Classes? • Region.wb : Waterbodies • Region.rch : Waterbody Reaches • Region.lm : Area Landmarks • Route.drain : Network Features • Route.rch : Linear Reaches • Route.lm : Linear Landmarks • nhdpt.pat : Point features • nhdduu.patdom : Digital Update Units (quad/cu bdy)

  5. Feature Issues • Unusual Features

  6. Feature Issues • Overlapping Features • Most common between lake/ponds and 2-D reaches • Other Cases: • 2-D: • swamp/marsh and lake/pond; • foreshore and sea/ocean; • rapids and 2-d stream/river • 1-D: • Bridge, Overpass, Canal • Issue: within same feature class (drawing order issue) or different feature class (no drawing order issue)

  7. Feature Issues • Overlapping Features (continued) • How to know: • Examine the NHD.RXP file • Where poly# is duplicated, you have overlapping features • Select out RCH features, then perform a frequency…Those records with count gt 1 are overlapping. • DEMONSTRATION….

  8. Finding Overlapping 2-D Features NHD.RXP File Select All but RCH Summarize by Poly# Count gt 1 are Overlaps

  9. Feature Issues • Overlapping Features (continued) • How to symbolize: • Choose ‘see through’ symbols • OR– choose which feature you care about more • Demo...

  10. 2-D Overlaps... Submerged Stream/River Lake/Pond Foreshore Sea/Ocean

  11. Feature Issues • Artificial Paths on Coastlines… • Problems: • Around Some Islands, Not Around Others • May Not Want to See Them Anyway • How to ‘Hide’ them • Reselect Reaches Having ‘Non-Flowing’ Connections • Do Left/Right Analysis to Find APs that Have Land on One Side AP on Coast

  12. Using NHD Attributes • NHD.FCODE • Contains Every Unique Combination of Feature and Attributes • Used for Distinguishing Between Perennial and Intermittent (e.g.) • Relate by FCODE, 5-digit code present in feature tables

  13. Feature Types vs. Attributes

  14. Using the NHDDUU Coverage • Contains the “Digital Update Units” • Currently the 1:100K Quads and CU that Make Up the Dataset • NHDDUU.PATDOM : Region Feature Class Containing Those Boundaries • With Future Updates, Could be Any Geographic Area

  15. FOD-ifacts • 2-D Features that Touch CU Boundary are Not Split… • Clever Use of DUU Can Hide Them… • Mask Areas by Selecting DUU Polys • Symbolize with Background Color (white) • Draw Those Polys on Top of 2-D Features

  16. Labeling NHD Features • Names are on: • Route.RCH: streams/rivers • Region.RCH: lake/pond • Region.WB: Other 2-D waterbodies • Region.LM: Big Dams, etc. • Route.LM: Small Dams, etc. • NHDPT: Springs, Seeps, Waterfalls, etc.

  17. Handling Multiple CUs • “One at a Time” is Tedious for Large Areas • Use append_NHD (available on NHD Web Site) • AML • Initial Release or Flow Validated Inputs, but Not a Mixture • Handles Overlaps/Duplicate Features, and Other Nastiness

  18. Displaying Reaches • What’s the Point Unless You Have Additional Information Related to Them? • Displaying Events • Displaying Flow, Displaying Stream Order, etc.

  19. Projections • NHD Delivered in “non-projected”, Decimal-Degree Coordinates • Project On-the-fly or Permanently for Proper Maps

  20. Scale Issues • At Small Scales, May not Want to Show 2-D Stream/Rivers, Use Drains Only, Symbolize APs Like Stream/Rivers • Make 2-D Feature Outlines Invisible • At Very Large Scales, May See APs Outside their 2-D Features • Quad Edge Problems More Apparent at Large Scales...

  21. Using NHD with Other Sources • The Usual Issues: • Registration • Scale • Source • DRGs • DOQQs • DEM/NED

  22. Happy Mapping!

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