The NOAA Coastal Services Center (CSC) requested the creation of benthic habitat data along the southern Texas coast to support the Texas Seagrass Monitoring Program.The benthic habitat map was created from 1m UltraCam digital airborne imagery collected in November 2007. The imagery was processed into 4-band DOQQs. The benthic habitat map was created from resampled 2m mosaicked orthos. Habitat classification was performed through segmentation of the imagery using Definiens Professional and habitat labeling through Classification and Regression Tree (CART) Analysis. The minimum mapping unit is100m2. This map covers San Antonio and Espiritu Santo Bays which is approximately 370mi2.
The NOAA CSC worked cooperatively with the Texas Parks and Wildlife Department (TPWD) and the Texas A and M University, Corpus Christi, Center for Coastal Studies to have benthic habitat data, primarily submerged aquatic vegetation, created for eight bay systems along the southern Texas coast. This project, the phase 2 project,consists of the two remaining bay systems, Lower Laguna Madre and San Antonio/Espiritu Santo Bays. This benthic habitat data will support the recently adopted Texas Seagrass Monitoring Program which calls for the monitoring of seagrass beds along the Texas coast for assessment of status and trends.
The geographic extent of the project area is ~370mi2. Benthic habitat data was generated from 2007 UltraCam imagery for all estuarine lands except for the marine side of the barrier beaches.
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NOAA Coastal Services Center
Horizontal accuracy of the reprocessed source imagery was verified to exceed the project specification of +/- 5meters CE95 of position on the ground.Overall habitat map final thematic map deterministic accuracy is 90% and overall fuzzy accuracy is 91%, which exceeds the contract standard of 85%. Additionally, 13 of the 14 final individual class producer's and user's deterministic accuracies exceed the contract standard of80%. The deterministic user's accuracy for emergent marsh is 76%. All of the individual class producer's and user's fuzzy accuracies exceed the contract standard of80%. Detailed error matrices can be found in the thematic accuracy report.
Eight photo-identified ground control check points were established for the purpose of assessing the accuracy of the final orthoimagery. These points were randomly distributed over the San Antonio Espiritu Santo Bay area.Two of the control points fell outside the project extent,and one additional point was discarded, as it was not associated with a well-defined feature. The five remaining points were used to calculate the accuracy of the orthoimagery.For the final map product Initial Map accuracy assessment was used as a tool to prioritize areas for further field examination and after field investigation to prioritize those areas where additional modeling or interpretation was needed. Error matrices showing both deterministic and fuzzy accuracies were compiled for the initial map. Based on the results compiled from the assessment, the team visit any classes exhibiting inaccuracy and addressed the classes through modeling, additional analysis or manual editing.
Compliance with the accuracy standard for the imagery was ensured by the placement of photo-identifiable ground control check points.Compliance with the accuracy standard for the final map product was ensured by field checks and manual editing.
The orthoimagery was produced by Sanborn Map Company, Inc. for NOAA. The imagery for the San Antonio Espiritu Santo Bay project was acquired on December 5,2007 and the orthoimagery and horizontal analysis was completed on January 28, 2007.
The original 1m DOQQs for the project area were resampled to 2m and mosaicked into a single four-band image. Image segmentation was performed using Definiens Professional. The classification of the habitat segments(as ESRI polygon shapefiles) was performed using CART analysis. The habitat map was refined with the aid of field data collected during May and July of 2008. The final habitat shapefile clipped to the final project area boundary. Each polygon has a unique polygon identification number in the attribute table (field"POLY_ID"). The final shapefile was checked for proper topology and to insure that each polygon has a correct habitat label, habitat code, modifier label if present, unique identification number, and an area calculation. Polygons below the 100m2 minimum mapping unit (MMU) were eliminated, though some polygons less than 100m2 were retained if their area changed to below the MMU due to the polygon boundary smoothing process. The habitat data also went through a independent validation review.Polygons in the habitat map labeled as Patchy SRV(seagrass) were used to mask the 2m mosaic for further classification of these areas. Pixels in the imagery falling within the Patchy SRV polygons were classified into a"percent seagrass" cover category using NDVI values.Pixels were classified into the following seagrass coverage categories:0% greater than 0-10% greater than 10-20% greater than 20-30% greater than 30-40% greater than 40-50% greater than 50-60% greater than 60-70% greater than 70-80% greater than 80-90% greater than 90%For each Patchy SRV polygon from the habitat map, the average percent seagrass coverage and standard deviation was calculated based on the coverage values of each pixel within the polygon. These data were included in the Patchy SRV shapefile attribute table.
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