C-CAP Territory of American Samoa (Tutuila) 2003-2010 Land Cover Change Analysis

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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.

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Process_Description

This dataset was created by Photoscience.

This dataset contains the classifications of 2003 imagery and 2010 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 625 possible from-to change combinations.

In this section of the metadata, the 2003 classification

procedure is described, then the 2010 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 (2003) Classification: This section outlines the classification procedure for the American Samoa (Tutuila) High Resolution C-CAP. Quickbird imagery used in producing this land cover product was also utilized in producing an associated impervious surfaces layer for the island. The mapping approach utilized a boundary summary and refinement procedure developed by Sanborn to leverage previous United States Forest Service mapping efforts to create the high resolution land cover data set. A calibration visit was conducted and training data was collected for classification. Non impervious features were mapped using a 0.25 acre minimum mapping unit (MMU).

This dataset was created by Sanborn (www.sanborn.com).

This version of the classification is the High Resolution Land Cover (2003) for the Island of Tutuila, American Samoa.

This section outlines the classification procedure for the Island of Tutuila, American Samoa High Resolution C-CAP. Quickbird imagery used in producing this land cover product was also utilized in producing an associated impervious surfaces layer for the island. The mapping approach utilized an object oriented approach. A calibration visit was conducted and training data was collected for classification. Non impervious features were mapped using a 0.5 acre minimum mapping unit (MMU).

Pre-processing steps:

The Quickbird mosaic utilized for this project was provided from GeoEye as an orthorectifed, georeferenced product and was consistent with the quoted 1:12000 spatial accuracy.

Field-Collected Data:

Training data was collected in the field between August 15th and 23th, 2009. Land cover observations were recorded by analysts. The referenced dataset went through a QA/QC procedure to ensure it met accuracy standards.

Classification:

Segmentation - Image segmentation was completed at multiple scales using the multispectral (2.4 m) imagery in order to group like spectral and textural objects within the imagery. For consistency, the associated impervious data set was incorporated into the segmentation layer as a boundary delimiter. Segments can share boundaries of an impervious surface, but can never overlap an impervious surface.

Automated Classification, image segments are classified using a decision tree classifier in See5 software and an iterative nearest neighbor classifier in Definiens software. Nearest neighbor training data is collected through analyst interpretation or ancillary data sets and used to calibrate the classification algorithm.

Automated Classification Refinement - Models are built to refine or reclassify land cover areas by utilizing the wealth of attribute information linked to each segment within Definiens.

Classification Edits - As with any automated or semi-automated land cover classification there are often inconsistencies in the land cover map. The final step before map finalization was to remove inaccuracies through manual segment labeling as interpreted by an analyst.

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

Metadata imported

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

Late Date (2010) Classification:

This data set was created by Photo Science Inc. (www.photoscience.com).

This version of the classification is the High Resolution Land Cover (2010-era) for the Island of Tutuila, American Samoa.

This section outlines the classification procedure for the Island of Tutuila, American Samoa High Resolution C-CAP. Non-impervious features were mapped using a 0.5 acre minimum mapping unit (MMU) and impervious features were mapped using a 0.1 acre MMU.

Pre-processing steps:

The WorldView2 imagery utilized for this project was provided from Digital Globe as an orthorectified, georeferenced product. Photo Science geo-referenced the 2003 C-CAP classification and the 2003 base imagery to the WorldView2 (as it has better horizontal accuracy) to co-register the data sets.

Classification:

The 2003 C-CAP classification was overlaid on the 2010 WorldView2 imagery with a semi-transparency. The classification was systematically reviewed at a scale of 1:2,500. Where land cover changes were identified the analyst would zoom into a larger scale and manually edit the map to reflect the 2010 ground conditions. The updated map then went through an independent review to further refine the classification. Image segmentation was run on the 2010 imagery in a buffered zone around all of the changed areas. The updated land cover was summarized by the image objects (segments) to replace hand delineated boundaries with boundaries based on image segmentation. This final step ensured a consistent look and feel across the high resolution C-CAP data sets.

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 2003 and 2010 datasets as inputs. The algorithm generates

a from-to file where each combination is uniquely labeled from 1 to 521.

Metadata imported