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Map-Making with the NHD Bill Wheaton Research Triangle Institute wdw@rti.org, (919) 541-6158
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Mapmaking with the NHD Topics Topics Map Design and Layout Using NHD Content in Maps Displaying Other Data with NHD
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Map Design and Layout Modern Tools Don’t Alleviate the Need for Proper 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.
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Feature Issues What are the NHD Feature Classes? 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)
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Feature Issues Unusual Features Unusual Features
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Feature Issues Overlapping Features Overlapping Features Most common between lake/ponds and 2-D reaches Other Cases: 2-D: swamp/marsh and lake/pond;swamp/marsh and lake/pond; foreshore and sea/ocean;foreshore and sea/ocean; rapids and 2-d stream/riverrapids and 2-d stream/river 1-D: Bridge, Overpass, CanalBridge, Overpass, Canal Issue: within same feature class (drawing order issue) or different feature class (no drawing order issue)
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Feature Issues Overlapping Features (continued) 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….
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Finding Overlapping 2-D Features NHD.RXP File Select All but RCH Summarize by Poly# Count gt 1 are Overlaps
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Feature Issues Overlapping Features (continued) Overlapping Features (continued) How to symbolize: Choose ‘see through’ symbols OR– choose which feature you care about more Demo...
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2-D Overlaps... Sea/Ocean Foreshore Lake/Pond Submerged Stream/River
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Feature Issues Artificial Paths on Coastlines… 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
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Using NHD Attributes NHD.FCODE 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
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Feature Types vs. Attributes
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Using the NHDDUU Coverage Contains the “Digital Update Units” 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
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FOD-ifacts 2-D Features that Touch CU Boundary are Not Split… 2-D Features that Touch CU Boundary are Not Split… Clever Use of DUU Can Hide Them… Clever Use of DUU Can Hide Them… Mask Areas by Selecting DUU Polys Mask Areas by Selecting DUU Polys Symbolize with Background Color (white) Symbolize with Background Color (white) Draw Those Polys on Top of 2-D Features Draw Those Polys on Top of 2-D Features
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Labeling NHD Features Names are on: 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.
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Handling Multiple CUs “One at a Time” is Tedious for Large Areas “One at a Time” is Tedious for Large Areas Use append_NHD (available on NHD Web Site) 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
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Displaying Reaches What’s the Point Unless You Have Additional Information Related to Them? What’s the Point Unless You Have Additional Information Related to Them? Displaying Events Displaying Events Displaying Flow, Displaying Stream Order, etc. Displaying Flow, Displaying Stream Order, etc.
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Projections NHD Delivered in “non-projected”, Decimal-Degree Coordinates NHD Delivered in “non-projected”, Decimal-Degree Coordinates Project On-the-fly or Permanently for Proper Maps Project On-the-fly or Permanently for Proper Maps
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Scale Issues At Small Scales, May not Want to Show 2- D Stream/Rivers, Use Drains Only, Symbolize APs Like Stream/Rivers 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 Make 2-D Feature Outlines Invisible At Very Large Scales, May See APs Outside their 2-D Features At Very Large Scales, May See APs Outside their 2-D Features Quad Edge Problems More Apparent at Large Scales... Quad Edge Problems More Apparent at Large Scales...
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Using NHD with Other Sources The Usual Issues: The Usual Issues: Registration Scale Source DRGs DRGs DOQQs DOQQs DEM/NED DEM/NED
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Happy Mapping!
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