C-CAP USVI, St. Croix 2007-2012 Land Cover Change Analysis

Date that the source FGDC record was last modified.

Converted from FGDC (Federal Geographic Data Committee) CSDGM (Content Standard 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 links to Distribution Info.

NOAA CSC | Source Geospatial Form: remote-sensing image | Type of Source Media: CD-ROM

Process_Description

This dataset, and the 2012-era classification was created by Dewberry. The 2007-era C-CAP classification was created by Sanborn.

This dataset contains the classifications of 2007 imagery and 2012 imagery. It is used for change analysis between these years. The attributes include a from-to change description category. There are 521 classes corresponding to the 521 possible from-to change combinations. In this section of the metadata, the 2007 classification procedure is described, then the 2012 change detection classification procedure is described. Finally in the post-processing section, the process of combining the maps to generate a spatial matrix of change is discussed.

Early Date (2007-era) Classification:

Pre-processing steps: The ADS40 was provided to Sanborn as a geo-referenced product. Sanborn performed a quality control on the imagery to check for pixel dropouts and other image issues. Individual image tiles were combined to create a single image for the entire island. The early date (2003-era) classification was created first using satellite data because at the time it was the most recent, cloud free imagery available. The late date (2007-era) ADS40 became available shortly after the early date classification was completed. The ADS40 imagery was found to have ortho-rectification accuracy. The 2003-era classifications and imagery were geo-rectified to co-register with the ADS40 imagery.

Change Detection: Once the images were aligned, the next step was to determine the areas of change between the 2003-era and 2007-era data. Since the 2003-era classification was already complete, it is only necessary to classify the areas of change to create a 2007-era classification of the same specifications. The 2007 ADS40 imagery was segmented with the 2003 land cover classification as a hard boundary delimter. Logical rulesets and thresholding based on the spectral properties of the imagery and the early date classification were used to generate a mask of potential change. The change mask was incorporated into the early date classification to create the draft late date classification. This map was further revised with rulesets and thresholding. The final step before map finalization was to remove inaccuracies through manual segment labeling as interpreted by an analyst. Sanborn used independent reviewer's comments to further refine the land cover map.

Map Finalization - Sanborn used independent reviewers comments to further refine the land cover map.

Attributes for this product are as follows:

0 Background

1 Unclassified

2 Impervious

3

4

5 Developed, Open Space

6 Cultivated Crops

7 Pasture/Hay

8 Grassland/Herbaceous

9 Deciduous Forest

10 Evergreen Forest

11 Mixed Forest

12 Scrub/Shrub

13 Palustrine Forested Wetland

14 Palustrine Scrub/Shrub Wetland

15 Palustrine Emergent Wetland

16 Estuarine Forested Wetland

17 Estuarine Scrub/Shrub Wetland

18 Estuarine Emergent Wetland

19 Unconsolidated Shore

20 Bare Land

21 Open Water

22 Palustrine Aquatic Bed

23 Estuarine Aquatic Bed

24 Tundra

25 Snow/Ice

Late Date (2012) Classification:

This section outlines the classification procedure for the St. Croix High Resolution C-CAP performed by Dewberry. The color-infrared imagery used in producing this land cover product was also utilized in producing an associated impervious surfaces layer for the island. This land cover is based on the 2007 high resolution St. Croix C-CAP dataset. Changes were identified using aerial photo interpretation of the 2007 dataset against the 2011-2012 imagery. A calibration visit was not conducted though NOAA had access to local resources for validation. Non impervious features were mapped using a 0.25 acre minimum mapping unit (MMU) and impervious features were mapped using a 0.1 acre MMU.

Pre-processing steps:

The 2011-2012 color-infrared imagery utilized for this project was provided from the USACE as an orthorectified, georeferenced product. The imagery was reviewed for radiometric errors, pixel dropouts, and other image issues. Individual image tiles were merged into a single mosaic and re-sampled from the native 1-foot spatial resolution to 1m.

Classification:

The 2007 C-CAP dataset was over-laid with semi-transparency on the 2011-2012 color-infrared imagery. It was panned at a scale of 1:5,000 and manually updated to match features in the 2011-2012 imagery. Analysts zoomed in to a larger scale when necessary to perform edits. The product went through a QC procedure to ensure features were accurately captured.

Map Finalization - Dewberry used independent reviewer's comments to further refine the land cover map.

Attributes for this product are as follows:

0 Background

1 Unclassified

2 Impervious

3

4

5 Developed, Open Space

6 Cultivated Crops

7 Pasture/Hay

8 Grassland/Herbaceous

9 Deciduous Forest

10 Evergreen Forest

11 Mixed Forest

12 Scrub/Shrub

13 Palustrine Forested Wetland

14 Palustrine Scrub/Shrub Wetland

15 Palustrine Emergent Wetland

16 Estuarine Forested Wetland

17 Estuarine Scrub/Shrub Wetland

18 Estuarine Emergent Wetland

19 Unconsolidated Shore

20 Bare Land

21 Open Water

22 Palustrine Acquatic Bed

Post-Processing Steps:

A GIS matrix algorithm was run with 2007 and 2012 datasets as inputs. The algorithm generates a from-to file where each combination is uniquely labeled from 1 to 625.

Metadata imported