Land Cover Interpretation and Mapping

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Land Cover Interpretation and Mapping

• Supplemental Material Lecture 1
• prepared by R. Lathrop 8/03

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Land Cover vs. Land Use

• Land Cover (LC) the biophysical material
  covering the earths surface
• Land Use (LU) how humans are using the land
  surface
• Examples land cover impervious
  surface land use parking lot land
  cover grass land use recreational field

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LU/LC Classification systems

• Classification system systematic categorization
  of LU or LC types
• Often hierarchical progressing from the general
  to the specific,
• e.g., level I --gt level II --gt level III
• Examples USGS LU/LC (Anderson et al., 1976)
  Coastal Change Analysis Program (CCAP)
• USFWS NWI (Cowardin et al., 1979)

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Existing USGS Land Cover Products
National Land Cover Dataset 1992 (NLCD 92) A
U.S. land cover classification product based
primarily on 1992 Landsat Thematic Mapper (TM)
data. MRLC2000 (Multi-Resolution Land
Characteristics 2000) Selected ETM and TM
scenes (Landsats 7 and 5) from the National Land
Cover Characterization 2000 project. Land Use and
Land Cover Data (LULC) Historical U.S. land
use and land cover data derived from 1970s and
1980s aerial photography. Global Land Cover
Characterization (GLCC) A global land cover
database primarily derived from 1992 to 1993 1-km
AVHRR data.
For more info http//edc.usgs.gov/products/landco
ver.html
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Photo Interpretation Keys

• Selective made up of typical illustrations and
  descriptions of objects in a given category
• Elimination hierarchical, requires the user to
  follow a step-by-step procedure, working from the
  general to the specific

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Mapping Considerations

• Uncontrolled maps prepared at photo scale by
  direct tracing. Area measurements no more
  accurate than from the photos directly, depends
  on flatness of the terrain
• Controlled maps transfer onto planimetric base
  map of uniform scale. Needed for precise
  measurement of area.
• Minimum Mapping Unit smallest area of land that
  is mapped as a separate unit or entity, depends
  on scale user requirements

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Visual Interpreting Land Cover

• Remember the 7 photo recognition elements
• Shape
• Size
• Shadows - shape height
• Tone/Color
• Texture
• Pattern
• Site
• Association

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More on color remember image color is a
function of the spectral reflectance pattern of
the object
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A color example-plant leaves

• Chlorophyll absorbs large of red and blue for
  photosynthesis- and strongly reflects in green
  (.55um) um
• Peak reflectance in leaves in near infrared
  (.7-1.2um) up to 50 of infrared energy per leaf
  is scattered up or down due to cell wall size,
  shape, leaf condition (age, stress, disease),
  etc.
• Reflectance in Mid IR (2-4um) influenced by water
  content-water absorbs IR energy, so live leaves
  reduce mid IR return
• In a CIR photo,

Hi NIR ------------gt Hi Red Very Lo Red
------------gt Very Lo Green Very Lo to Lo
Green -----------gt Very Lo to Lo Blue As a
result due to the additive color processes, the
color would be Red to Magenta
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Spectral reflectance characteristics are both
spatially and temporally variable. For example,
each leaf is different and can change
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Photo Interpreting Natural Vegetation Communities

• Site is important determinant of the vegetation
  community type due to differences in microclimate
  and soil characteristics (e.g. texture, moisture
  status). I.e., certain community types are
  associated with certain site types.
• Topoclimate north-facing aspects have a colder
  microclimate than south-facing aspects
• Soil Catena ridge-tops are drier than valley
  bottoms

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Photo Interpreting Natural Vegetation Communities

• To identify trees to species type, often need to
  identify by crown shape - either from a vertical
  perspective or shadowed silhouette
• Photo interpretation keys available for this
  purpose
• Remember as scale changes from large to small the
  crown shape of individual trees eventually merges
  to form the overall texture of the forest canopy

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Vegetation Mapping Applications

• Forest stand mapping for timber evaluation -
  species identification - timber volume
  density, canopy closure, tree height
• Plant vigor, disease and stress detection
• Wildlife habitat mapping
• Outdoor recreation capability surveys

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Cultural Features Identification

• Building size, shape and associated features
• Major transportation routes highways and
  rail-lines, canals/ports, airports
• Street pattern and density
• Open/green spaces vegetation type and cover

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Major categories of urban land use

• Industrial
• Commercial/service
• Transportation/utilities
• Institutional (schools, government)
• Residential
• Recreational

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Industrial Classification Key

• Extraction characterized by excavations, piles,
  ponds, tanks, earth-moving equipment
• Processing characterized by bulk material
  storage, large processing equipment, power
  plant/smokestacks, waste piles/ponds
• Fabrication characterized by few facilities for
  storing bulk materials, 1 story warehouse type
  buildings, rail/truck transportation

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Urban-Cultural applications

• Parking and transportation studies
• Residential development analysis indicators of
  housing quality real estate evaluation
• Brown-fields location/evaluation
• Open space location/evaluation

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Engineering Applications

• Large projects site location/evaluation
• Transportation route location/selection
• Construction material surveys
• Natural hazard investigations
• Post-disaster damage surveys
• Monitoring disturbed land
• Water pollution investigations