IKONOS imagery was purchased to support the Pacific Islands Geographic Information System (GIS) project and the National Ocean Service's (NOS) coral mapping activities. One-meter panchromatic and four-meter multispectral data were purchased for the Territory of Guam. A digital vector shoreline was manually digitized from the one-meter panchromatic imagery to provide accurate, up-to-date shoreline data for the region.
The Pacific Islands Geographic Information System (GIS) project is a multiyear initiative designed to increase the use of GIS and related spatial technology in the coast resource management programs of the Territories of American Samoa and Guam, the Commonwealth of the Northern Marian Islands (CNMI), and the State of Hawaii. The project will focus on personnel, training, equipment, software, data, and applications. Where appropriate, other related activities in the region will be incorporated into the effort.
ground condition
Data set is not for use in litigation. While efforts have been made to ensure that these data are accurate and reliable within the state of the art, NOAA cannot assume liability for any damages, or misrepresentations, caused by any inaccuracies in the data, or as a result of the data to be used on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
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These data are believed to be logically consistent, though no tests were performed. All arcs were snapped by the nodes to create consistently tied strings without node dangles. Line geometry is topologically clean.
This shoreline dataset of Guam is dependent on the shoreline as delineated on 2001 through 2003 IKONOS digital satellite imagery from Space Imaging, LLC. The position of the shoreline might change as the natural land changes or better maps and more recent imagery become available.
The data were created by delineating the shoreline off of IKONOS panchromatic digital satellite imagery collected in 2000 - 2003. The horizontal resolution of the digital imagery is 1 meter. The original scale of the imagery was 1:3780. During orthorectification of the IKONOS imagery, 73 ground control points were used to determine the circular error (CE) at a 90% confidence level. For Pacific Islands, Guam, IKONOS data, 2002 the circular error is 8.5 meters for the panchromatic data set.
Used to identify and digitize the shoreline (land/water interface) for Guam
Used to identify and digitize the shoreline (land/water interface) for areas of the coast that were obscured by cloud cover in the satellite imagery
Used to identify and digitize the shoreline (land/water interface) for locations where the coast was obscured by cloud cover in the satellite imagery
During the vectorization process, the satellite imagery was displayed on a computer screen using ESRI's ArcGIS 8.2 software. In order to obtain the highest degree of accuracy from the imagery, the one-meter panchromatic imagery was used as a base layer for digitizing. In an effort to better visualize the land-water interface, the one-meter imagery was overlaid on top of the four-meter multispectral imagery using a 35 % transparency value. The near-infrared band (Band 4) was used in the display of the multispectral imagery. The resultant base layer contained the one-meter resolution of the panchromatic imagery and the colorization of the four-meter imagery. The display was zoomed to the image resolution of the panchromatic imagery and the shoreline was manually digitized. All lines are coded with length, ID, origin, and source. Note - Areas of the shoreline that were obscured by cloud cover in the satellite imagery were digitized from USGS Digital Raster Graphics (DRGs). The USGS DRGs for Guam were adjusted in the x and y directions using ERDAS Imagine 8.5 to match the IKONOS imagery. IKONOS imagery used were collected 20001017, 20001130, 20010511, 20010511, 20010514, 20021111, 20021114, 20030105, 20030116. This step began 20020905 and ended 20030923.
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Further modification of the Guam shoreline was conducted by staff within the Guam Coastal Zone Management Program and modified by staff of the NOS Biogeography Program. ArcView 3.2 was used to adjust shapefile vector vertices. Most alterations were done by combining the visual information available within the one-meter panchromatic imagery of Guam together with local knowledge of the coastline, and some Digital Ortho Quad (USGS DOQ) data.
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Internal feature number.
ESRI
Feature geometry.
Feature identification number
NOAA Coastal Services Center
Length of shoreline polyline segments
Origin of shoreline data
Guam Coastal Zone Management Program
Source of shoreline data
One-meter panchromatic IKONOS digital satellite imagery
USGS Digital Raster Graphics (DRG)
USGS Digital Ortho Quad Photos
Users must assume responsibility to determine the appropriate use for these data. Disclaimer- While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
