High-Resolution Orthorectified Imagery for Three Target Areas in Lake Clark National Park and Preserve (LACL), Southwest Alaska

ABSTRACT

This data series consists of orthorectified aerial photography for the coastal and nearshore areas of Lake Clark National Park and Preserve (LACL) of southwestern Alaska. The images cover three selected target areas: Glacier Spit, Silver Salmon, and Tuxedni Bay. The series consists of three timeslices: from 1993, 1978, and approximately 1950. The orthoimages were completed as part of a pilot study in collaboration between the University of Colorado (Institute of Arctic and Alpine Research) and the National Park Service (Southwest Network Inventory and Monitoring Program). Each high-resolution image has the qualities of a photograph and the functionality of a map layer for use in Geographic Information Systems (GIS) or remote sensing software. The eight orthorectified frames for 1993 are derived from 1:24,000-scale, black and white photographs acquired by Walker Alaska (now Aero-Metric) for the National Park Service (NPS). They have a pixel resolution of 0.3 m, an average relative horizontal accuracy of 7.2 m and cover a total of 200 km². The three orthorectified frames for 1978 are derived from 1:65,000-scale, color-infrared (CIR) photographs acquired by the USGS and NASA, as part of the Alaska High Altitude Photography (AHAP) program. They have a pixel resolution of 1.0 m, an average relative horizontal accuracy of 17.3 m and cover a total of 675 km². The five orthorectified frames for 1954 to 1957 are derived from 1:43,000-scale, black and white photographs acquired by the US Air Force. They have a pixel resolution of 0.6 m, an average relative horizontal accuracy of 15.5 m and cover a total of 500 km². Digital scans of the photographs from ca. 1950, 1978 and 1993 were fully orthorectified in ERDAS Imagine using air-photo camera models, a Digital Terrain Model (DTM), information from calibration reports, and image-to-image control points linked to 2004-2006 IKONOS orthoimagery. This orthorectification procedure was refined after extensive testing of various software packages and settings. Horizontal errors could be reduced even further for small areas with minor adjustment.

Each of the 16 image files is in georeferenced .tif (GeoTIFF) format. Accessory shapefiles consist of attributed index map layers. All of the data layers share an Alaskan Albers projection and NAD83 datum, and are provided with FGDC-compliant metadata (in .html, .txt, and .xml formats). Also provided are a README file and a PowerPoint visual overview of the data series. Together, the three datasets make up a total of 91 files and 8.9 GB of data. The imagery is available through an unrestricted public license, and can be obtained on DVD by request (see Distributor contact information in the metadata).

The high-resolution imagery will be of interest to land managers, scientists, and others for observation and analysis of natural features and ecosystems. The orthoimagery complements recent IKONOS collections, and greatly improves both the resolution and accuracy of the previously georectified LACL coastal atlas. Beyond investigation of coastal erosion for these target areas, the three timeslices will be helpful to assess the status of environmental features, and to detect change in: 1) cultural resources and archeological sites; 2) ecosystem components such as geology, soils, lake and stream hydrology, and vegetation assemblages; and 3) marine, terrestrial, and freshwater habitats for a variety of animals. The imagery assists the goals of the NPS Southwest Alaska Network Inventory and Monitoring Program.

METADATA AND CITATION

PLEASE READ the FGDC-compliant metadata files that are available for each file (in .html, .txt, and .xml formats), which provide numerous details that may be of interest. Please cite this data release as: Manley, W.F., Lestak, L.R., and Parrish E.G., 2008, High-Resolution Orthorectified Imagery for Three Target Areas in Lake Clark National Park and Preserve (LACL), Southwest Alaska: Anchorage, AK: National Park Service, Southwest Alaska Network I&M Program. Digital Media.

CONTACT US

RELEVANT LINKS

• NPS Southwest Alaska Network Inventory and Monitoring Program
• INSTAAR QGIS Lab: Coastal Erosion of Southwest Alaska Parks
• NPS Alaska Region Geographic Information Systems

FILE LIST

* This image has been compressed in .zip format.