Land Use and Land Cover

1. Land use and land cover
   land use - reflects people's relation to the environment
   land cover - natural/artificial compositions at the surface

   the USGS classification system (Anderson et al., 1976)
        - most commonly used national classification system for remote
            sensing data (both satellite images and air photos)
        - based on land capability, vulnerability to management, and
            potential use

2. Classification criteria
   1. interpretation accuracy of lulc categories should be 85%+
   2. the accuracy of several categories should be about equal
   3. repeatable results should be obtainable by different
        interpreters and sensing time
   4. the system should be applicable over extensive areas
   5. the categories should be used as surrogates for activity
   6. the system should be suitable for data obtained at different
        times of the year
   7. subcategories can be obtained from finer scale data
   8. aggregation of categories must be possible
   9. comparison with future lulc should be possible
  10. multiple use of land should be recognized when possible

   minimum areas and image resolution
        Depend on
        - the scale and resolution of the source data
        - the scale of data compilation or image interpretation
        - the final scale of the map
        - no less than 0.25cm~0.5cm on a side on a map

   expanded classifications
        - the USGS classification system is aimed at level I and II
        - level I and II are adequate for planning and management
        - the two levels are adequate for monitoring lulc changes
        - the system is open-ended and allows levels of subcategories

3. Plant classification
   floristic
        - a botanical classification, e.g. species, genus, family
   physiognomy (life form)
        - physical form of plants, e.g. tree, shrub, herbaceous
        the two systems may not relate to each other

        RS classification is more commonly based on life form
        floristic classification is possible only when fine
        resolution image is available or in pure stand situation
 

Digital Elevation Models
      Made available by USGS, state agencies, and private vendors

1. 1:24,000 DEM
    Developed and distributed by USGS

       A regular grid in UTM coordinate system

       A 7.5 by 7.5 minute coverage

       Data are ordered from south to north in profiles that are ordered from west to east
       30 by 30 meter spacing along and between profiles

       The profiles do not always have the same number of elevation points

       The measuring unit is meter in most cases
 

2. 1:250,000 DEM
    Developed by Defense Mapping Agency and distributed by USGS

    A regular grid in geographical coordinate system

    A1 by 1 degree coverage

    Spacing along profiles is 3 arc-second

    Spacing between profiles is 3 arc-second below 50N latitude, 6-9 arc-second otherwise
 
 
 
 
 
 

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