C-CAP Molokai 2005 era High Resolution Land Cover Metadata

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NOAA OCM | Source Geospatial Form: remote-sensing image | Type of Source Media: DVD/CD-ROM

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

This version of the classification is the High Resolution Land Cover (2005-era) for the Island of Molokai, HI.

Summary:

This section outlines the classification procedure for the Molokai 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 C-CAP 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 0.5 acre minimum mapping unit (MMU).

Pre-processing steps:

The Quickbird mosaic utilized for this project was provided from Digital Globe as an orthorectified, georeferenced product and was consistent with the quoted 1:12000 spatial accuracy. In conjunction with the Quickbird mosaic, Sanborn used an air photo mosaic from the USGS for the island collected in 2004 as well as a DTM created from a 5m radar collect for the island. The original return image from the radar was also utilized.

Field-Collected Data:

Training data was collected in the field between March 30th and April 11th, 2008. Land cover observations were recorded by analysts. The referenced dataset went through a QA/QC procedure to ensure it met accuracy standards.

Classification:

Initial 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. The initial segments were created at a larger scale (scale refers to the target size and shape of like features generalized by Definiens software) of 100. Larger segments are required to leverage the 30 m data sets and incorporate the IFSAR data that is collected at spatial resolution of 5 m. 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.

Rule set Creation - The initial map of the island of Molokai is created by incorporating an existing C-CAP 2001 land cover data set through a logical rule set created by a Sanborn analyst. The rules are created such that image segments are labeled to the C-CAP classification scheme based on their underlying medium resolution components.

Initial Label and Edits - The automated labeling procedure created a reasonable representation of land cover using the labeling routine, however errors did occur. Gross inaccuracies in the data product that would inhibit the further classification of the segments at a smaller scale factor were corrected through knowledge based models or manual edits.

Secondary Segmentation - Further refinement of the map is only possible though classification of the image segments directly. Classification of the image segments is a hierarchical process, whereby larger scale segments are composed of smaller scale segments. The initial segmentation was used to further aid in the automated classification of the secondary (more detailed) image segments. The final scale factor for the mosaic was 35.

Automated Classification - Automated classification of the image segments is accomplished through a process modeling incorporated within Definiens software. Models are built to refine or reclassify land cover areas by utilizing the wealth of attribute information linked to each segment within Definiens. In a small amount of cases, the nearest neighbor classification routine was used to refine segments. Nearest neighbor training data is collected through analyst interpretation or ancillary data sets and used to calibrate the classification algorithm.

Automated 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. The change detection process used to create the 2010 Molokai C-CAP product highlighted some errors in the 2005 land cover map. To create a more accurate product these issues we addressed by NOAA through a combination of spatial models and manual edits. While the changes may not be large in area and/or be directly reflected in the accuracy assessment, we feel the products more accurately reflect the land cover for the time period.

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

Metadata imported