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DEMs, LULC

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for record examples: http://edc.usgs.gov/glis/hyper/guide/usgs_dem#7m12 ... from the U.S. Geological Survey's EROS Data Center Distributed Active Archive ... – PowerPoint PPT presentation

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Title: DEMs, LULC


1
DEMs, LULC Soil data
  • INLS 110-111
  • GIS Digital Information
  • Uses, Resources Software Tools

2
DEMs Digital Elevation Models
  • Raster model digital data
  • Federal Agency Dept of Interior
  • US Geological Survey (USGS) National Mapping
    Division
  • Widespread format scales available correspond
    to DLGs

3
DEM Background
  • Consist of sampled array of elevs. for a number
    of ground positions at regularly spaced
    intervals.
  • Composed of integer values in grid form
    topographic map hypsography overlay
  • Available in 7.5-minute, 15-minute, 2-arc-second
    (also known as 30-minute), and 1-degree units.

4
DEM Usage
  • Used for generating graphics
  • isometric projections displaying slope, direction
    of slope (aspect), terrain profiles between
    designated points.
  • Also combined with other data types
  • stream location data and weather data to assist
    in forest fire control
  • with remote sensing data to aid in the
    classification of vegetation.

5
DEM Applications
  • Modeling terrain gravity data for use in locating
    energy resources
  • Determining the volume of proposed reservoirs
  • Calculating the amount of material removed during
    strip mining
  • determining landslide probability
  • developing parameters for hydrologic models

6
DEMs Creation
  • Some created by scanning National High Altitude
    Photography (Level-1)
  • Others derived from DLG data or photographs
    incorporating
  • elements from hypsography
  • (contours, spot elevations)
  • elements from hydrography
  • (lakes, shorelines, drainage) (Level 2 3)
  • Beware projections datum's vary

7
USGS -United States Geological Survey
  • Produces 5 primary types of elevation data
  • 1 degree DEM (SMALL SCALE)
  • ( 3 x 3 arc second spacing)
  • 2 arc second/30 min DEM (MEDIUM SCALE)
  • (2 x 2 arc second spacing)
  • 7.5 minute DEM (LARGE SCALE)
  • (30 x 30 meter spacing)
  • 7.5 min Alaska DEM
  • (1 x 2 arc second spacing)
  • 15 minute Alaska DEM
  • (2 x 3 arc second spacing)

8
DEMs Three Classification Levels
  • Level-1
  • elevation data sets in standardized format
  • Intended for 7.5 min DEMs (large scale)
  • Created by scanning NHAP
  • Accuracy vertical RMSE of 7 meters desired, 15
    meters max. permitted

9
DEMs Three Classification Levels
  • Level-2
  • elevation data sets processed or smoothed for
    consistency edited to remove errors.
  • Derived from hypsographic hydrographic
    digitizing
  • Accuracy a RMSE of one-half the contour interval
    is max. permitted.

10
DEMs Three Classification Levels
  • Level-3
  • data sets derived from DLG hypsography
    hydrography data incorporates selected elements
    from both
  • Accuracy a RMSE of one-third of the contour
    interval is max. permitted.

11
DEM RESOLUTION
  • defined as separation between elevation points on
    horizontal grid
  • elevation points equally spaced
  • Two common ways to specify separation
  • meters used in Universal Transverse Mercator
    (UTM) grids when linear measurements specify
    distance
  • arc seconds used in geographic coordinate
    grids when angular measurements specify distance

12
DEMs Available
  • Large Scale
  • Spacing 30 x 30 meter UTM projection for each
    7.5 x 7.5 min block also 15 x 15 minute units
    163,360.
  • Correspond to USGS 124,000 and 125,000 scale
    topographic quadrangle map series for US its
    territories.
  • Alaska 7.5-minute DEM data correspond to the same
    scales, but unit sizes vary depending on the
    latitudinal location of the unit. Projection
    coordinate systems also differ.

13
DEM 124,000 30 meter format
14
DEMs Available
  • Intermediate Scale
  • Spacing 30 x 30 minute areas (2-arc-second)
  • Correspond to east or west half of USGS 30 x 60
    minute (1100,000) topographic quadrangle map
    series for the conterminous US Hawaii.
  • Each 2-arc-second unit is produced and
    distributed as four 15 x 15-minute cells. The
    spacing of elevations along and between each
    profile is 2 arc seconds.

15
DEMs Available
  • Small Scale
  • Spacing 1 x 1 degree blocks (3 x 3 arc-second
    spacing)
  • Coverage available for contiguous US, Hawaii, and
    most of Alaska.
  • 10 DEMs referred to as 3-arc-second or 1250,000
    scale DEM data.
  • Basic elevation model produced by or for the DMA
    (Defense Mapping Agency), but distributed by USGS
    in DEM data record format. In reformatting the
    product, USGS doesnt change basic elevation
    information.

16
DEM 1250,000 3-arc format
Image Source Clarke, Keith C. (2001). 3rd Ed.
Getting Started with Geographic Information
Systems. p 95. Fig. 3.18.
17
DEM Image shaded to show topography
Scranton, PA East 1250,000 DEM.
Image Source Clarke, Keith C. (2001). 3rd Ed.
Getting Started with Geographic Information
Systems. p 95. Fig. 3.18.
18
Raster Graphic DEM Examples
Large Scale Sturgis, SD DEM (7.5 minute)
Jewel Cave Nat'l Monument, SD
Intermediate Scale Sheridan, Wyoming DEM (30
minute)
Small Scale Yellowstone DEM (1 degree block)
19
DEM Data Organization
  • DEM files organized into three logical records
  • Type A contains information defining DEM
    characteristics, including name, boundaries,
    units of measurement, min./max. elevations,
    projection parameters, number of type B
    records.
  • Type B contains profiles of elevation data
    associated header information.
  • Type C contains statistics on the accuracy of
    the data.

for record examples http//edc.usgs.gov/glis/hype
r/guide/usgs_dem7m12
20
National Elevation Dataset (NED)
  • Seamless data
  • based on 1 arc second spacing most of US 2 arc
    for Alaska
  • variety of elevation units, horizontal datums,
    projections
  • uses geographic coordinates NAD 83 horizontal
    NAVD 88 vertical datum

21
North American Digital Elevation Model- ESRI
derived from the global DEMGTOPO30 data sets
from the U.S. Geological Survey's EROS Data
Center Distributed Active Archive Center (EDC
DAAC)
22
North American Shaded Relief - ESRI
  • derived from the global DEMGTOPO30 data sets
    from the U.S. Geological Survey's EDC DAAC

23
Shaded relief generated from raster elevation
data portrays the land surface. Shown combined
with the topographic map content from the USGS
digital raster graphic of Juneau, Alaska.
24
LULC - Land Use Land Cover
  • Vector model Raster Models of digital data
  • Federal Agency Dept of Interior
  • US Geological Survey (USGS) National Mapping
    Division
  • Widespread format primary scale 1250,000
  • All LULC data conform to the Universal Transverse
    Mercator (UTM) projection.

25
LULC Content
  • Files describe
  • vegetation, water, natural surface, and cultural
    features on the land surface.
  • Uses Anderson Classification System
  • The USGS provides these data as part of its
    National Mapping Program.
  • LULC mapping program designed to compliment
    standard topographic maps (scales of 1250,000
    some cases1100,000)

26
LULC Creation
  • Manual interpretation of aerial photographs from
    NASA high-altitude missions other sources
  • Secondary sources from earlier land use maps
    field surveys also used (as needed)
  • Later digitized to create a national digital LULC
    database. (resulting GIRAS)
  • National Land Cover Dataset

27
LULC Vector Image
Image Sourcehttp//edcwww.cr.usgs.gov/glis/graphi
cs/guide/1_250_lulc/figure1.gif
28
2 Formats Vector (GIRAS) or Raster (CTG)
  • Available for most of the contiguous US Hawaii
  • Distributed in the GIRAS or CTG formats through
    anonymous FTP (for free)
  • FTP files are available sorted by state
  • 1250,000-scale sorted by state
  • 1100,000-scale sorted by state

29
VECTOR Geographic Information Retrieval
Analysis System (GIRAS)
  • Fixed length records (ASCII) each may consist of
    1 to 16 data-element fields.
  • Each data-element field may be one of 3 types
  • 16 bit binary integer
  • 32 bit binary integer or
  • a string of text characters.
  • file structure map header, section header, arc
    records subfile, coordinate subfile, polygon
    records subfile, file of arcs by polygon (FAP)
    subfile, text subfile and an associated data
    subfile.
  • Topological Vector Model

30
RASTER Composite Theme Grid (CTG)
  • Files are sequential and consist of fixed length
    records (except for header files)
  • One grid cell for each logical record.
  • Grid cells contain point sample of the quad where
    the center point of each cell is 200 meters apart
    from other center points in adjacent cells.
  • cells mapped to the UTM projection

31
LULC Applications
  • Compatible w/variety of USGS other data
  • Example socioeconomic data compiled by the
    Bureau of Census can be compared to LULC data
  • Frequently used in conjunction with DLG and DEM
    data to assist in
  • river basin planning, barrier island change
    analysis, environmental impact statement
    preparation urban development studies.

32
LULC Examples
  • LULC Gwynns Falls Watershed, Baltimore Cty, MD
  • Upper Susquehanna-Lakawanna Watershed

33
Other Popular Data types
  • Soil Data for GIS - Overview
  • STATSGO State Soil Geographic Database
  • SSURGO Soil Survey Geographic Database
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