Fall 2011 SAV Classification

The sub-aquatic vegitation map for was produced for the SAV Technical Working Group under a cooperative workplan with BP. The SAV map was derived from 0.3 meter resolution visible and near-infrared imagery collected by Aerometric. The imagery was segmented into homogeneous image objects following an object-based image analysis (OBIA) approach. The image objects were subsequently classified using Classification and Regression Tree (CART) statistical analysis. Manual edits based on air photo interpretation were performed to correct obvious errors and refine the map. A draft map was reviewed by USGS personnel and final edits made based on their comments. The polygons were dissolved based on the class assignments and a minimum mapping unit of 4 square meters was enforced.

This dataset was created to provide a comprehensive assessment of the distribution and extent of submerged aquatic vegetation (SAV) off-shore of Petit Bois, Horn Islands, and Chandeleur Islands after the Deep Water Horizon oil spill.

Attribute information can be found in the feature class attribute table.

Fields in the Feature Class Attribute Table: OBJECTID = Internal feature number Shape = Feature geometry (ie polygon) ClsFnlQC_AreaSwitch = Class value, where 1 = SAV Shape_Length = Length of feature in meters Shape_Area = Area of feature in square meters SAVCls = Final Class value, where 1 = SAV

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The shallow waters off the northern shore of Petit Bois Island, Horn Island, and Chandeleur Islands.

These data may be provisional and restricted to Trustees within a Natural Resource Damage Assessment.

The user is responsible for the results of any application of this data for other than its intended purpose.

These metadata may be provisional and restricted to Trustees within a Natural Resource Damage Assessment.

These metadata may be provisional and restricted to Trustees within a Natural Resource Damage Assessment.

While NOAA makes every effort to ensure that its databases are error-free, errors do occur. We ask that you notify us immediately of any errors that you discover in our data.

Horizontal positional accuracy is based on the accuracy of the aerial imagery provided by Aerometric. The imagery collected and orthocorrected by Aerometric met the ASPRS Class 2, 1:24,000 scale accuracy standards which limit the RMS in X or Y to 4 ft. Mismatches between adjacent images averaged less than 3 pixels and did not exceed 6 pixels.

The SAV mapping was restricted to the leeward side of the islands. No mapping was performed on the Gulf side of the islands where wave energy is generally too strong for SAV to prosper.

The data attribute fields were checked for bad values and consistency of values.

The Spatial Data Branch publishes this data on behalf of the originator. Data visually represented in ERMA are aimed to guide responders, decision makers, and users in making informed steps of analysis and action.