DLGs

1
DLGs DEMs

• INLS 110-111
• GIS Digital Information
• Uses, Resources Software Tools

2
Digital Line Graphs (DLGs)

• Vector model digital data
• Federal Agency Dept of Interior
• US Geological Survey (USGS) National Mapping
  Division
• Widespread format contains important data

3
USGS US Geological Survey

• Established  March 3, 1879, by President Hayes
  on recommendation of the National Academy of
  Sciences.
• 1st Mission "Classification of the public lands,
  examination of the geological structure,
  mineral resources, products of the national
  domain."
• The USGS is the Nation's largest water, earth,
  biological science and civilian mapping agency. 
• National Center in Reston, Virginia

4
DLGs Creation

• Created using manual or automated digitizing
  methods
• Derived from either aerial photographs or
  cartographic source material

5
DLGs Available

• Large Scale
• 124,000 and 125,000
• (125,000 and 163,360 for Alaska 130,000-scale
  maps for Puerto Rico)
• Derived from primarily USGS 7.5-minute
  topographic quadrangle maps
• Coverage contiguous US, Hawaii, the Virgin
  Islands

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Vector Model DLG
Image Source Clarke, Keith C. (2001). 3rd Ed.
Getting Started with Geographic Information
Systems. p. 90
7
Vector Graphic DLG Example
Image Source Clarke, Keith C. (2001). 3rd Ed.
Getting Started with Geographic Information
Systems. p. 91
8
DLGs Available

• Intermediate Scale
• 1100,000
• Derived from USGS 1100,000-scale, 30 x 60-min.
  quadrangle maps
• Coverage being collected for the contiguous US
  Hawaii
• If maps not available, (BLM) Bureau of Land
  Management planimetric 1100,000 maps used

9
DLGs Available

• Small Scale
• 12,000,000
• Derived from Natl Atlas of USA
• Organized two ways
• By section
• historical files between 1973-1980 (Alaska)
• Coverage All 50 States
• By State
• recent files between 1990 - 1994
• Coverage conterminous US Hawaii not Alaska
• Planimetric categories for all 50 States

10
DLGs Data Pending

• Large Scale (124,000)
• Goal national coverage (all 50 states)
• Intermediate Scale (1100,000)
• Hydrography transportation categories complete
  for contiguous US Hawaii
• Goal national coverage in all categories
• Product Status Update
• DLG Coverage 7.5 or 1100,000

see
11
Base Categories 124,000 maps

• Political boundaries
• (e.g., State, county, city, other municipal
  boundaries)
• Administrative boundaries
• (e.g., National State forest boundaries)
• Hydrography
• (e.g, all flowing water, standing water,
  wetlands)
• PLSS data describing rectangular system of land
  surveys administered by the BLM, referencing
  property boundaries
• (e.g., township, range, park information)

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Base Categories 124,000 maps (continued)

• Transportation data, including major
  transportation systems collected in three
  separate overlays
• (roads trails railroads pipelines,
  transmission lines, miscellaneous
  transportation features)
• Other significant manmade structures, including
  miscellaneous cultural features not in the other
  major data categories
• (e.g., schools, churches, hospitals)
• hypsography

see
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Base Categories 124,000 maps (continued)

• Surface cover, including information about
  vegetative surface cover
• (e.g., woods, scrub, orchards, and vineyards)
• Nonvegetative surface features, including
  information about the natural surface of the
  Earth
• (e.g., lava sand)
• Survey control markers
• (i.e., points of established position
  third-order or better elevations used as fixed
  references in positioning correlating map
  features).

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Base Categories 1100,000 maps

• Hydrography, including flowing water, standing
  water, and wetlands
• Transportation collected in 3 different
  categories (roads trails railroads
  pipelines, transmission lines, miscel.
  transportation)
• Hypsography, including contours supplementary
  spot elevations
• Boundaries, including State, county, city,
  other Natl State lands ie. forests parks
• PLSS, including township, range, section
  information.

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Base Categories 12,000,000 maps

• Boundaries
• Hydrography
• Manmade features
• Pipelines, transmission lines, miscellaneous
  transportation features
• Railroads roads and trails
• Public Land Survey System (PLSS)

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DLGs Use Different Coordinate Systems

• 124,000 Scale UTM
• 1100,000 Scale UTM
• 12,000,000 Scale Albers Equal-Area Conic

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DLG Files Bonus Info

• 2 data files in ASCII format for each State
  containing airport names populated place names
  with population figures.
• 2 national files 1 with land grant names
  identifiers 1 with Federal Information
  Processing Standard (FIPS) five-digit codes for
  all States, State equivalents, counties, county
  equivalents.
• Records in these data files can be associated
  with cartographic features contained in the DLG
  files.

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DLGs Data Organization

• Data are organized in graphic, optional,
  standard, or Spatial Data Transfer Standard
  (SDTS) formats
• The DLG optional format is topologically
  structured is widely used with GIS technologies
• If youre interested in specifics see
  http//edc.usgs.gov/glis/hyper/guide/usgs_dlgdlg1
  1