Coastal Bend Texas Benthic Habitat - Lower Laguna Madre 2004 Substrate

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Sample of benthic cover data

Date that the source FGDC record was last modified.

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details.

Partial upload of Positional Accuracy fields only.

Partial upload to move data access FTP links to Distribution Info and remove broken URLs.

The digital orthophotography was developed from imagery

acquired as part of the 2004 overflight of the State of

Texas developed for the USDA National Agricultural

Imagery Program (NAIP). In order to achieve a horizontal

accuracy of 5 meters, CE90 it is necessary to reprocess

the imagery incorporating new GPS field control. It should

be noted that the imagery was not tide coordinated so tidal

variation may exist between sorties. The imagery was

acquired between November 3, 2004 and November 7,

2004.

| Source Geospatial Form: remote-sensing image | Type of Source Media: digital

TerraSurv, Inc. of Pittsburgh, PA was contracted by

EarthData International of Frederick, MD to perform a

geodetic control survey in support of mapping an area

along the southeasterly coast of Texas between Port

Lavaca and Brownsville. Thirty-eight photo identifiable

locations were surveyed to provide ground control and

quality assurance checks for the mapping. Twenty of the

stations were used for mapping control and eighteen of the

stations were used for quality checks. The horizontal

datum was the North American Datum of 1983, CORS

adjustment (NAD 1983 CORS). The vertical datum was the

North American Vertical Datum of 1988 (NAVD 1988).

| Source Geospatial Form: model | Type of Source Media: paper

The original 1m DOQQs for the project area were

resampled to 2m and mosaicked. For habitat classification,

the mosaicked imagery was divided into two processing areas; one

set of two mosaics for true color and one set of two mosaics

for color-IR. Image segmentation was performed using on

the blue, green, red, and near-infrared bands for each of

the six processing areas. The classification of the habitat

segments (as ESRI polygon shapefiles) was performed

using CART analysis. The habitat maps for each of the two

areas was refined with the aid of field data collected during

July, August, and October 2007. The two processing area shapefiles

were edgematched and combined into a single shapefile which was

clipped to the final project area boundary and then clipped into three

separate shapefiles; north, middle, and south regions. Adjacent

regions do not overlap. Each polygon, within and across all three

delivery regions, has a unique polygon identification number. Each

shapefile was checked for proper topology and to insure that each

polygon has a correct habitat label, habitat code, modifier label if

resent, unique identification number, and an area calculation.

Polygons below the 100m2 minimum mapping unit (MMU) were

eliminated, though some polygons <100m2 were retained if their

area changed to below the MMU due to the polygon boundary

smoothing process. The habitat data also went through an

independent validation review. Accuracy assessment was performed

on seven classes with Patchy SRV and Continuous SRV being

combined into a single accuracy class. For field data collection,

non-random sites in the form of polygons were chosen by analysts

with an attempt to sample all available image signatures. These

sites were visited in the field and data on each site was collected

directly into digital format (ESRI shapefile) using a laptop or onto a

paper form that was later entered into digital format. Sites were

navigated to primarily using a Garmin GPS 76 unit connected to a

Panasonic Toughbook laptop displaying the project imagery and

polygons in ArcMap v9.1 or using the GPS unit alone. Habitat

classification was estimated as accurately as possible using

methods or combination of methods which included above water

observation, snorkeling, wading, and underwater video. This data

was entered into an ESRI shapefile via a digital field form in ArcMap

specifically developed for this type of field data collection. More

sample polygon sites were collected in-office based on the in-field

collected sites in order to meet the 30 sites per class accuracy

assessment requirement. For each class, a random selector macro

in ArcMap was used to randomly select 30 sites for accuracy

assessment. The entire pool of accuracy sites was kept separate

from the remaining sites and only used for accuracy assessment

during the project. Anonymity of the accuracy sites was maintained

throughout the project because it was unnecessary to ever visually

review these sites in order to perform the accuracy analysis. More

accuracy assessment sites were collected in a later field collection to

add to the analysis. These sites were chosen by randomly selecting

polygons within specific regions that were pre-determined to be visited.

Information for these sites was collected using the same methods for

the other sites. Accuracy information was compiled using ArcMap. The

zonal stats tool in ArcMap was used to determine the majority map

class each accuracy polygon intersected with. An accuracy

assessment error matrix was generated using this information by

importing it to Microsoft Excel and building the matrix. Both

deterministic and fuzzy accuracy assessment were performed. The

accuracy analysis and error matrices are presented and discussed

in the Lower Laguna Madre Final Accuracy Assessment Report.

The data were converted from a single ESRI polygon shapefile classified according to the System for Classifying Habitats in Estuarine and Marine Environments (SCHEME) to the Coastal and Marine Ecological Classification Standard (CMECS) 2012 format (which can be found at https://coast.noaa.gov/digitalcoast/tools/cmecs-crosswalk) which produces separate geoform, substrate, and substrate feature layers from the original input benthic habitat dataset. This substrate feature layer contains CMECS substrate component attributes where an "Equal" or "Nearly Equal" SCHEME value was present in the original data. Polygons for which no substrate information was present have been removed. No other changes to the original polygon boundaries or any other alterations of the original SCHEME data were made during this process.