North Carolina Seagrass Submersed Rooted Vasculars 1990 Substrate

A GIS data set of polygon data interpreted from aerial photography taken by NOAA/NOS Photogrammetry Branch depicting areas of Aquatic Beds of Rooted Vascular Plants in coastal north Carolina. Predominantly submersed rooted vasculars (SRV) but including some floating rooted vasculars (FRV). The nomenclature and definitions originally developed according to the Coastal Land Cover Classification System for the NOAA Coastal Change Analysis Project (C-CAP), Journal of Coastal Research 9(3):862-872 have been crosswalked into the Florida System For Classification of Habitats in Estuarine and Marine Environments (SCHEME) to build consistency with similar NOAA developed benthic data sets.

Original contact information:

Contact Org: NOAA Office for Coastal Management

Phone: 843-740-1202

Email: coastal.info@noaa.gov

To improve the understanding of coastal photic submersed lands and their linkages with wetlands and uplands, and with living marine organisms. To assist government agencies and others in making resource management decisions through the use of GIS.

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Photointerpretation with a Wild AVIOPRET stereoscope. Photographs and data were compiled on a Bausch and Lomb stereo zoom transfer scope at a scale of 1:24,000 on USGS 7.5' topographic maps or on NOAA shoreline topographic sheets scaled to 1:24,000 (original scale 1:20,000). Data is a merge of several coverages dependent on map base, photo mission, and photographic scale.

NOAA provides no warranty, nor accepts any liability occurring from any incomplete, incorrect, or misleading data, or from any incorrect, incomplete, or misleading use of the data. It is the responsibility of the user to determine whether or not the data is suitable for the intended purpose.

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Attribute accuracy for habitat polygons has not been

conducted. Field checks of all benthic signatures present

in the photographs were conducted to resolve those benthic

features that potentially could be confused with submersed

rooted vegetation. The number and locations of site visits

were based on judgment of the photointerpreter who led the

field verification phase of the surface level sampling. In

a second type of surface level work, a grid randomly placed

on a nautical chart determined the nominal latitude and

longitude of stations. These were sampled for species of

submersed rooted vegetation and ancillary environmental

information. The methodology was inappropriate for accuracy

assessment of the remotely based habitat data for three

reasons. 1) Any plants within a quarter mile radius of the

stations coordinates were sampled and indicated as positive

in the field database. Rare occurrences of small clusters of

plants would not be mapped from the photographs due to the

minimum mapping unit. 2) Navigation to stations was

accomplished with LORAN C which was spatially much less

accurate than was expected with the photographic approach.

Reference data must be a more reliable source than the data

to be evaluated. 3) Some nominal station locations were

unexpectedly deep or unsafe to approach or sample and were

arbitrarily moved to an adjacent more appropriate location.

This could have biased the spatial sampling.

Horizontal positional accuracy has not been established for the data set. National Map Accuracy standards (at a

compilation scale of 1:24,000) are assumed as the

theoretical optimal accuracy of this data. Accuracy is

limited by the accuracy and temporal coincidence of base

map and interpretation of the aquatic bed data from

photographs. In the case of USGS 7.5' topographic maps, the cultural information is more contemporary (up to 10 or 15

years out of date) than the geographic information (up to

45 years out of date). NOAA shoreline and cultural data

(based on 1988 and 1991 photography) are within six years

of the aquatic bed photography. The dearth of cultural

information throughout most of the study area resulted in a dependency on geographic features for local horizontal

control of the photographic data. The aquatic bed

photographs were more consistent with contemporary NOAA

shoreline topographic map bases (from 1988 and 1991)

photography and use of these map bases presumably

increased overall accuracy of the vegetation map. Aerial

photography is registered by local horizontal control to

base maps in a zoom transfer scope. Reference features are readily identifiable and can be accurately positioned on

the photograph and on the base map. Cultural feature are

preferred and geographic features are used if necessary. The base maps are USGS 7.5' topographic series or NOAA shoreline topographic sheets.

The SRV data carries no vertical attributes and no

assessment or measure of vertical accuracy was conducted.

The classification scheme includes one class at the Class

level and one at the Subclass 1 level within the SCHEME

system. All SRV within the study area were delineated,

unless flagged in the data set, to a depth of approximately

10 feet lower mean low water (MLLW), deeper than aquatic

beds are known to grown in the study area. Limited parts of

the study area were not successfully photographed and

therefore data for those locations are omitted from the

coverage. The photography provides a record of only a

single time period so that ephemeral beds not present at

the time of photography are omitted. This may be the case

for some Zostera marina beds, for example, which can sprout

from seed in the late spring and die due to heat stress and

exposure in the summer. Zostera marina is a perennial grass

which over winters as rhizomes within the substrate.

The classification scheme comprehensively includes all

subtidal bottom classified for the presence or absence of

submersed rooted vegetation. Void areas exceeding minimum

mapping unit were mapped within vegetation polygons and are

delineated and labeled. Overlay of the compiled and

digitized polygons of vegetation included a few instances

of overlap with dry land on the map base. This was

particularly true for data compiled on 7.5' map bases due

to the time differential between the photographic dates for

the map bases (typically 1940s for shorelines and 1970's or

1980's for cultural features) and the aquatic bed

photography (1985 to 1990) The shoreline moved in some

cases. Logical consistency in terms of topology for

vegetation polygons was confirmed in ARC/INFO and test plots

of the digitized data at the compilation scale (1:24,000)

were compared for consistency and similarity of

cartographic style with the source maps and were edited if necessary.