North American Carbon Program

1
Sub-pixel Analysis of a 1-km Resolution
Land-Water Mask
Latha Baskaran, Bob Cook and Suresh Kumar
Santhana-Vannan
Environmental Sciences Division Oak Ridge
National Laboratory Oak Ridge, TN 37830
North American Carbon Program
Alaska (North of 60N)
Sub-pixel Land-Water Mask

• Introduction
• The North American Carbon Program (NACP) is
  designed to quantify the magnitudes and
  distributions of carbon sources and sinks,
  explain the processes controlling them, and
  produce a consistent analysis of North America's
  carbon budget. The Modeling and Synthesis
  Thematic Data Center (MAST-DC) supports NACP by
  providing data products and data management
  services needed for modeling and synthesis
  activities.
• In many NACP or other projects modeling
  activities, it is often necessary to mask or
  exclude regions in water. A land-water mask is a
  data layer that delineates regions in land and in
  water and is useful for this purpose.
• On a continental and global scale, a MODIS data
  based land-water mask is widely used and is one
  of the only products available for the whole of
  North America. This MODIS based land-water mask
  is at a resolution of 30 arc-seconds or
  approximately 1-km and delineates water features
  such as oceans, shoreline, lakes etc. A 250-m
  MODIS land-water mask is being developed, but may
  not be available for several years.
• Higher resolution water layers are available for
  North America, but the data are from different
  sources and hence are at different levels of
  accuracy (spatial and temporal).
• However, to take advantage of the fine
  resolution water data, we developed a 30
  arc-second resolution map that captures sub-pixel
  information about land and water areas. The map
  contains the percentage of water within each 30 x
  30- arc second pixel.
• This sub-pixel product will be useful as a water
  mask, and will also serve to understand the 30
  arc-second MODIS based land-water mask product.

The National Land Cover Dataset is a Landsat
based land cover database prepared by a
consortium of agencies called Multi-Resolution
Land Characteristics (MRLC) Consortium. The
classification scheme includes a water category
which includes water bodies and generally has
less than 25 cover of vegetation or soil.
Canada (North of 60N)
United States and Canada (South of 60N)
The National Topographic Data Base (NTDB)
comprises of digital vector data sets that cover
the entire Canadian landmass. The NTDB includes a
layer for hydrographic features.
The Shuttle Radar Topography Mission (SRTM)
obtained elevation data on a near-global scale to
generate a high-resolution digital topographic
database of Earth (February of 2000). The SRTM
water body dataset was produced from 1 arc-second
digital terrain elevation data by the National
Geospatial-Intelligence Agency (NGA).
Comparison of MODIS based Land-water mask and
Sub-pixel Land-water mask for the Mid Continent
Intensive (MCI) Region

• Within shallow Inland Water (Inland Water lt5-km
  from shore OR lt50m deep),
• containing more than 75 water 74.5
• containing 50 - 75 water 10.5
• containing 25 - 50 water 6.9
• containing less than 25 water 8.1
• Within Ocean Coastlines and Lake Shorelines (LAST
  land pixel)
• containing more than 75 water 8.7
• containing 50 - 75 water 8.8
• containing 25 - 50 water 13.1
• containing less than 25 water 69.4
• Within Land
• containing more than 75 water 0.2
• containing 50 - 75 water 0.4
• containing 25 - 50 water 0.9
• containing less than 25 water 98.5

Acknowledgements This poster is based upon work
supported by the National Aeronautics and Space
Administration under Agreement No. NNH06AE47I
issued through the Terrestrial Ecology Program,
Earth Sciences Directorate.