ed1d1003-3c74-496e-aebf-c369a5845e74_source eng; USA utf8 dataset Metadata manager 907-451-5020 3354 College Road Fairbanks AK 99709-3707 USA pointOfContact 2011-12-30 ISO 19115 Geographic Information - Metadata ISO 19115:2003/Cor.1:2006(E) 2 row 10291 column 10045 area Digital elevation model (DEM) and shaded relief image of Okmok Caldera, 2010 2011-01-01 publication State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys Fairbanks AK, USA publisher Schaefer, J.R. originator Larsen, J.F. originator Unema, J.A. originator http://dx.doi.org/10.14509/23223 mapDigital Raw Data File RDF 2011-6 1 DVD In response to significant morphologic changes in Okmok Caldera due to the phreatomagmatic eruption of Okmok volcano in 2009, a new digital elevation model was acquired to document and quantitatively assess the new volcanic features and altered hydrology within the caldera. This DEM dataset provides elevation data derived from a stereo pair of Worldview-1 satellite images acquired on January 21, 2010. In addition to the DEM, a shaded-relief image is also provided for easy visualization of the data. The DEM dataset provides high-resolution elevation data for Okmok Caldera. The georeferenced shaded relief map of Okmok Caldera provides a basemap for visualization of new geographic features following the 2008 eruption The original DEM was created by 'i-cubed: information integration & imaging LLC'; the initial Worldview images were provided by Rick Wessels, U.S. Geological Survey, Alaska Volcano Observatory. completed Alaska Division of Geological & Geophysical Surveys GIS Data Manager/GIS Analyst 907-451-5029 (907) 451-5020 3354 College Rd Fairbanks AK 99709-3707 USA pointOfContact notPlanned http://www.dggs.alaska.gov/webpubs/dggs/rdf/thumbnails/rdf2011-6-okmok-shaded-relief-browse.jpg A low resolution jpg image file derived from the higher resolution tif shaded relief image okmok_shaded_relief.tif JPEG Shaded Relief Digital Elevation Model theme Alaska Division of Geological & Geophysical Surveys Okmok Okmok Caldera Okmok Volcano place Alaska Division of Geological & Geophysical Surveys The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products, any failure thereof, or otherwise, and in no event will the State of Alaska's liability to the requester or anyone else exceed the fee paid for the electronic service or product. otherRestrictions Use Constraints: Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product. otherRestrictions Access Constraints: This content is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below). grid eng; USA geoscientificInformation Native Dataset Environment: .tif raster format with a .tfw worldfile -168.300000 -167.98600000 53.2970000 53.4890000 2010-01-21 This publication is composed of both a digital elevation model (DEM) and a shaded-relief image of the Okmok Caldera. To minimize the download times, the files are offered as two separate zip files. This metadata file describes both the DEM file and the shaded-relief image. The DGGS metadata standard extends the FGDC standard to include elements that are required to facilitate our internal data management. These elements, referred to as 'layers', group and describe files that have intrinsic logical or topological relationships. The layers are named to correspond with the name of the file: >rdf2011-6-okmok-dem-21-jan2010 DEM dataset provides elevation data of the Okmok Caldera, georeferenced TIFF format (.tif and .tfw files) >rdf2011-6-okmok-shaded-relief shaded relief image of the Okmok Caldera, georeferenced TIFF format (.tif and .tfw files) true Entity and Attribute Information Entity and Attribute Overview: There are no attributes other than the elevation values for the individual pixels and the encoded values for easting and northing coordinates. There are no attached attribute tables. There are no attributes other than the pixel values of 0 to 254 gray-scale for the individual pixels and the encoded values for easting and northing coordinates. There are no attached attribute tables. Entity and Attribute Detail Citation: this report this report GeoTIFF unknown State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys 907-451-5020 907-451-5050 3354 College Road Fairbanks AK 99709-3707 USA dggspubs@alaska.gov 8 am to 4:30 pm, Monday through Friday, except State holidays Please view our website (http://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible. distributor see http://dx.doi.org/10.14509/23223 Free download http://dx.doi.org/10.14509/23223 GeoTIFF CSDGM IMPORT ERROR: No digtinfo/formcont information dataset Horizontal Positional Accuracy Report Based on several years of fieldwork and thus familiarity with the geographic features around Okmok volcano, in addition to known locations of GPS survey sites, there are several point locations that can be accurately identified on the new DEM surface. A comparison of horizontal position was made by plotting these known locations along with the new DEM in a GIS. See Horizontal Positional Accuracy Explanation for more details. Horizontal Positional Accuracy Based on several years of fieldwork and thus familiarity with the geographic features around Okmok volcano, in addition to known locations of GPS survey sites, there are several point locations that can be accurately identified on the new DEM surface. A comparison of horizontal position was made by plotting these known locations along with the new DEM in a GIS. The high-confidence, visually-identifiable points, lie within 2-pixels on the DEM. The new DEM cell size is 2 meters, thus the horizontal accuracy is determined to be within 4 m. meters 4 Vertical Positional Accuracy Report Assessment of the DEM vertical accuracy is complicated by the high rate of erosion and changing surface hydrology that occurred between the image acquisition date of January 21, 2010 and the RTK GPS survey seven months later in August of 2010. The most significant vertical changes due to erosion occurred within the caldera in areas with the most ash fall. As a first step to assessing the vertical accuracy of the DEM, only sites outside the caldera that experienced less than 2 cm of ash fall were used to compare the surveyed point values to the DEM cell values. See Vertical Positional Accuracy Explanation for more details. Vertical Positional Accuracy Assessment of the DEM vertical accuracy is complicated by the high rate of erosion and changing surface hydrology that occurred between the image acquisition date of January 21, 2010 and the RTK GPS survey seven months later in August of 2010. The most significant vertical changes due to erosion occurred within the caldera in areas with the most ash fall. As a first step to assessing the vertical accuracy of the DEM, only sites outside the caldera that experienced less than 2 cm of ash fall were used to compare the surveyed point values to the DEM cell values. Only one RTK survey point (RTK37; 53.30573, -168.04795 WGS84; Z = 83.171 m) and one campaign GPS site (OK29; 53.427560, -168.264581 WGS84; Z=447.512 m) met this criteria. The vertical cell value of the DEM minus the GPS surveyed point (delta z) are as follows: RTK37, 0.029 m; OK29, 0.490 m. Two points is not ideal to ascertain vertical accuracy, so other points within the caldera were considered. Two other RTK GPS survey points RTK29 (53.462999, -168.09027 WGS84; Z = 356.974 m) and RTK30 (53.46529, -168.09308 WGS84; Z = 355.14), were located near the gates along a stream channel. Comparison of the Worldview-1 image from Jan. 21, 2010, a satellite image from March 31, 2010, and fieldwork in August 2010, it appears that these two sites experienced less than 1 m of vertical erosion. Delta Z for these two sites are as follows: RTK29, 0.633 m; RTK30, 0.597 m. Thus a conservative vertical estimate of the accuracy of the DEM is determined to be +/- 1 m. meters 4 The DEM coverage area is limited to the size of the original Worldview-1 image stereo pair and thus does not encompass the entire volcano and is mostly centered about the caldera. The DEM coverage area is limited to the size of the original Worldview-1 image stereo pair and thus does not encompass the entire volcano and is mostly centered about the caldera. Several campaign GPS sites and RTK surveyed GPS sites were plotted in a GIS along with the DEM to ensure that both horizontal placement and vertical Z values were reasonably accurate. This lineage was generated by the FGDC CSDGM to 19139 transformation On January 21, 2010, DGGS-AVO acquired Worldview-1 commercial stereo satellite imagery (spatial resolution of ~1 m), 17 months after the phreatic eruption of Okmok volcano. 2010-01-01T00:00:00 In August 2010, we surveyed image-identifiable points around the volcano using a Trimble Real Time Kinematic (RTK) Global Position System (GPS). This system provides centimeter-level horizontal and vertical accuracy. 2010-08-01T00:00:00 We submitted six RTK surveyed points within the caldera and one point outside the caldera to the commercial vendor, ‘i-cubed: information integration and imaging LLC’, for the creation of a digital elevation model (DEM). 2010-09-01T00:00:00 The commercial vendor, i-cubed, delivered the DEM in tif format, readable in ArcMap. We used the Copy Raster tool in ArcMap to create a new DEM, setting the NoData value to -32767. From this new DEM, we used Arc 3D Analyst (default settings of: Azimuth = 315, Altitude = 45, and Z factor = 1) to create a shaded-relief image. 2011-12-01T00:00:00 Determination of Horizontal Accuracy: We accurately identified several point locations, based on several years of fieldwork and thus familiarity with the geographic features around Okmok volcano, combined with known locations of GPS survey sites. We made a comparison of horizontal position by plotting these known locations, along with the new DEM, in a GIS. The high-confidence, visually-identifiable points lie within 2 pixels on the DEM. The new DEM cell size is 2 meters, thus we determined the horizontal accuracy to be within 4 m. 2011-12-01T00:00:00 Determination of Vertical Accuracy: DEM vertical accuracy assessment is complicated by the high rate of erosion and changing surface hydrology that occurred between the image acquisition date (January 21, 2010) and the RTK GPS survey seven months later (August 2010). The most significant vertical changes resulting from erosion occurred within the caldera in areas with the most ash fall. As a first step to assessing the vertical accuracy of the DEM, we used only sites outside the caldera that experienced less than 2 cm of ash fall to compare the surveyed point values to the DEM cell values. Only one RTK survey point (RTK37) and one campaign GPS site (OK29) met this criteria. The vertical cell value of the DEM minus the GPS surveyed point (delta z) are as follows: RTK37, 0.029 m; OK29, 0.490 m. Two points is not an ideal number of samples to ascertain vertical accuracy, so we considered other points within the caldera. We identified two other RTK GPS survey points (RTK29 and RTK30) near the gates along a stream channel. We compared the Worldview-1 image from Jan. 21, 2010, with a satellite image from March 31, 2010, and fieldwork in August 2010; we concluded that these two sites experienced less than 1 m of vertical erosion. Delta Z values for these two sites are: RTK29, 0.633 m; and RTK30, 0.597 m. Thus we determined a conservative vertical estimate of the accuracy of the DEM is +/- 1 m. 2011-12-01T00:00:00 otherRestrictions Metadata Use Constraints: If the user has modified this metadata file in any way, the user is obligated to describe the types of modifications the user has made. User specifically agrees not to misrepresent this metadata file, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. unknown This metadata was automatically generated from the FGDC Content Standard for Digital Geospatial Metadata standard (version FGDC-STD-001-1998) using the 2019-08-12T11:11:00 version of the FGDC CSDGM to ISO 19139 transform. Metadata manager 907-451-5020 3354 College Road Fairbanks AK 99709-3707 USA pointOfContact