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Introduction
Modern Landscape View
The coverages of the Modern Landscape View of the EcoAtlas
Baylands share common aerial photography origin. They are
based on the best available existing regional digital information
on baylands habitats. However, substantial local inaccuracies
in this existing digital data have been revealed through intensive
local reviews held by SFEI in December 1996 through the present.
The following documentation summarizes the origin of version
1.0 of the EcoAtlas Modern Landscape View.
Substantial revision of the Modern Landscape View to incorporate
hundreds of changes recommended by local experts through
truthing sessions, changes in the landscape since 1985,
and to implement the more detailed and regionally-representative
Habitat Typology of the Goals Project is currently taking
place. As a result of these changes a substantially more
detailed and accurate Modern Landscape View will be available.
Version 1.0 Habitat Types
- Shallow Bay or Strait, Open Water
- Intertidal Flat
- Tidal Marsh
- Farmed Bayland
- Grazed Bayland
- Salt Pond
- Managed Wetland
- Managed Bayland, Perennial Pond
1. Origin of Coverages
Major Source:
National Wetlands Inventory, U.S.F.W.S, 1985
Important Additional Sources:
- USGS 7.5' Quadrangles
- BCDC Diked Baylands Study
- Tidal Marshlands Mapping, K. Dedrick
Discussion of Data Integration:
Several sources of information are incorporated into version
1.0 of the of the EcoAtlas Modern Landscape View. The dominant
source is reported to be the National Wetlands Inventory
(NWI) for the Bay Area. The NWI was compiled from color
infrared aerial photographs at a scale of 1:58,000. The
flights occurred in April 1985 at approximately mean high
water (MHW). These photographs were used to produce 7.5
minute mylar maps, which were then digitized and made available
to the public as Digital Line Graph files. The source(s)
of these DLG files has not been ascertained.
The DLG files were imported into GRASS and used as the
shoreline and upland boundaries. Individual parcel boundaries
were digitized at SFEI using USGS 7.5' quadrangle paper
maps (24,000 scale). The digitizer precision was +/- 0.005",
and the RMS error averaged under 5 meters per quad. The
first draft of the EcoAtlas was created in GRASS, and translated
to ARC/INFO using the v.out.arc command (this converts the
GRASS vector files to ARC/INFOs "generate" file format).
All subsequent topological and feature attribute table updates
were done in ARC/INFO.
Updates were of two types:
- The reclassification of parcel types;
- creation, deletion, or modification of parcel boundaries
from information hand drawn or traced on USGS 7.5' quad
sheets or 24,000 scale copies of the EcoAtlas. When boundaries
were added or changed, the pertinent information was almost
always represented as DLG-derived or 7.5' series quadrangle
sheet digitized arc feature type data, and added to the
EcoAtlas using the "put" command in Arcedit.
Individual parcels of intertidal flat are delimited by
the major creeks and rivers that enter the Estuary, and
by the boundaries of contiguous study plots established
by the Point Reyes Bird Observatory. Parcels of tidal marshlands
are delimited by natural tidal channels that extend from
the shoreline of a estuarine bay or river to the upland
margin of the Estuary, or that surround some marshland and
cause it to be an island. Parcels of diked baylands are
delimited by constructed levees that support a light-duty
truck road or larger roadway.
Version 1.0 of the EcoAtlas Modern Landscape View received
initial review for accuracy and completeness by the public
and by representatives of the California Department of Fish
and Game, California Department of Water Resources, and
the United States Fish and Wildlife Service in 1995. Corrections
resulting from these reviews were incorporated into the
EcoAtlas. Further, more intensive review by local experts
was initiated in December 1996 and will result in an updated
version with substantially increased detail and accuracy.
2. Discussion of Uncertainty and Future Data Development
During December 1996 to February 1997, truthing sessions
for the EcoAtlas Modern Landscape View 1.0 were held in
the four major subregions of the Bay Area. Sessions in Fremont
(South Bay), Richmond (Central Bay), Yountville (North Bay),
and Suisun (Grizzly Island) invited local experts to participate
in review, reclassification, and correction of the EcoAtlas.
These sessions have resulted in hundreds of recommended
changes drawn on plots of the EcoAtlas and entered into
standardized datasheets. The changes documented during the
truthing process reflect the Bay Area wetland community's
best knowledge of the region's habitats. Participants include
much of the agency staff, environmental community, academic
scientists, and private landowners with recognized expertise
on current baylands habitats.
Data collected in the truthing process will make the following
improvements to the baylands of the EcoAtlas:
- Correct boundary errors
- Implement the more detailed, locally-developed Habitat
Typology
- Incorporate landscape change since 1985
We estimate that these changes will affect more than half
the approximately 2100 polygons in the EcoAtlas. To implement
these changes, SFEI has acquired the 1995/96 United
States Fish and Wildlife Service - Pacific Region Infrared
aerial photography for the Bay Area, apparently the first
photographic mission since 1985 to make possible a set of
imagery with consistent resolution, quality, and date for
the entire geography of Bay Area baylands and watersheds.
Photographs will be scanned at high resolution (600 dpi)
and registered to digital USGS data to form a composite
photographic basemap for the EcoAtlas.
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