Identification_Information: Citation: Citation_Information: Originator: Schaefer, Janet R. Publication_Date: 2005 Title: 30-meter shaded relief image of Okmok Volcano, Umnak Island, Alaska Geospatial_Data_Presentation_Form: georeferenced TIFF Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2005-01 Publication_Information: Publication_Place: Fairbanks, AK Publisher: State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys Other_Citation_Details: 1 CD Online_Linkage: \\craton\library\okmok\publications\RDF2005-01 Description: Abstract: This 30-meter, horizontal, cell-size, shaded relief, georeferenced TIFF image of Okmok Volcano, Umnak Island, Alaska, was created by combining digital elevation model (DEM) data provided by NASA's shuttle radar topography mission (SRTM) and the aircraft-mounted synthetic aperture radar (AirSAR) mission. Purpose: This georeferenced TIFF was created to be used as a base layer for other geographic information system (GIS) projects that display geographic or geologic data pertaining to Okmok Volcano and eastern Umnak Island. This shaded relief image displays topographic features for all of Okmok Volcano, and a small area to the east, across Umnak pass, on Unalaska Island. Supplemental_Information: SRTM and AirSAR DEM datasets were combined in ArcGIS to produce a georeferenced shaded relief TIFF image of Okmok Volcano. The bulk of the image is based on the SRTM data, but many data holes or shadows in the original SRTM data have been filled in with the AirSAR data to create a better display. Missing data appears as black pixels, especially in steep terrain. The TIFF image is in a UTM projection, zone 2N, using the WGS84 datum. Bounding coordinates in map units (meters) are: left bounding coordinate: 631096.298330; right bounding coordinate 768421.324621; top bounding coordinate: 5990943.682763; bottom bounding coordinate: 5874110.898761. The cell size of the image is 30.003283 meters by 30.003283 meters. The SRTM data was collected during an 11 day mission in February 2000, and the AirSAR data was collected on October 17, 2000. Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 20000212 Currentness_Reference: ground condition Status: Progress: Complete Maintenance_and_Update_Frequency: none planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -169.046430 East_Bounding_Coordinate: -166.904289 North_Bounding_Coordinate: 54.050037 South_Bounding_Coordinate: 52.949343 Keywords: Theme: Theme_Keyword_Thesaurus: none Theme_Keyword: Okmok Theme_Keyword: Umnak Island Theme_Keyword: shaded relief Theme_Keyword: Aleutian Arc Theme_Keyword: Volcano Place: Place_Keyword_Thesaurus: none Place_Keyword: Okmok Volcano Place_Keyword: Okmok Place_Keyword: Umnak Island Place_Keyword: Fox Islands Place_Keyword: Umnak Place_Keyword: Aleutian Arc Access_Constraints: This report, map, and/or data set are available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below). Use_Constraints: Any hardcopies or published data sets utilizing these data sets 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. User specifically agrees not to misrepresent these data sets, 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. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: State of Alaska, Division of Geological & Geophysical Surveys Contact_Position: Alaska Volcano Observatory Geologist III Contact_Address: Address_Type: mailing and physical address Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907) 451-5010 Contact_TDD/TTY_Telephone: Not Available Contact_Facsimile_Telephone: (907) 451-5050 Contact_Electronic_Mail_Address: dggspubs@dnr.state.ak.us Hours_of_Service: 8 am to 5 pm Monday through Friday, except State holidays Contact_Instructions: Please address all comments or questions to the e-mail address above whenever possible. Browse_Graphic: Browse_Graphic_File_Name: Okmok30mshade_browse.jpg Browse_Graphic_File_Description: 500 x 425 pixel, grayscale, 1-bit, 26KB, JPEG of Okmok30mshade Browse_Graphic_File_Type: JPEG Data_Set_Credit: Shuttle Radar Topography Mission (SRTM) DEM data is available for download courtesy of NASA. AirSAR data was provided by NASA JPL via Rick Guritz at the Alaska SAR Facility (ASF) Native_Data_Set_Environment: This georeferenced TIFF comes with both an ESRI world file (.tfw) and a MapInfo tab (.tab) file and can be used in any GIS software that reads a tif/tfw or tif/tab pair. The TIFF is a 17MB, 1-band grayscale, 8-bit, unsigned integer file. Cross_Reference: Citation_Information: Originator: Begét, James E. Originator: Larsen, Jessica F. Originator: Neal, Christina A. Originator: Nye, Christopher J. Originator: Schaefer, Janet R. Publication_Date: 2005 Title: Preliminary volcano-hazard assessment for Okmok Volcano, Umnak Island, Alaska Geospatial_Data_Presentation_Form: map, raster digital data, vector digital data Series_Information: Series_Name: Report of Investigations Issue_Identification: RI 2004-03 Publication_Information: Publication_Place: Fairbanks, AK Publisher: State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys Other_Citation_Details: 1 sheet, scale 1:150,000 Online_Linkage: \\craton\library\okmok\publications\RI2004-03 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: RGB values of the hillshade were computed from the DEM data using ESRI software Arc 8.2 3-D analyst extension. Logical_Consistency_Report: Shaded relief image was checked for accurate display of topographic features with on-the-ground inspection (geologic fieldwork), helicopter overflights, and imagery sets such as Landsat7, airphotos, and IKONOS. Completeness_Report: This shaded relief image displays topographic features for all of Okmok Volcano, and only a very small area to the east, across Umnak pass, on Unalaska Island. It was originally intended as a base layer for the display of geographic, geologic, and volcano-hazard features of Okmok Volcano, at a scale of 1:150,000. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: Sub-meter horizontal/vertical accuracy GPS points that were acquired during the summer field season 2000 and 2001 were used to assess the geospatial accuracy of IKONOS remotely sensed imagery. The GPS data collection points were chosen so that they would be visible and distinguishable on the imagery. In a GIS, the GPS points were overlain on the georeferenced IKONOS imagery. The horizontal geospatial accuracy of the remotely sensed imagery was determined to be less than 15 meters. This imagery was then used as the geospatially accurate reference to determine the accuracey of the DEM data. A 10-meter contour map was made of each DEM data set. The contour map based on the SRTM DEM data was overlain on the sub-15-meter accurate IKONOS imagery. Visual inspections at a zoom scale of 1:3,000 determined that the horizontal accuracy was correct and no adjustments were made to the SRTM DEM data. The contour map based on the AirSAR DEM data, however, appeared to be inaccurate (creeks did not line up with V-contours, high points did not line up with high-point closed contours, etc.). At a zoom scale of 1:3,000, ten visually distinguishable points were chosen to determine an X-shift and Y-shift needed to align the AirSAR DEM-derived contour data to the imagery. Results (average and standard deviation reported): X = 41 +/- 9 meters, Y = 198 +/- 19 meters. A shift of X = -41 and Y = 198 was applied to the AirSAR DEM data set. Quantitative_Horizontal_Positional_Accuracy_Assessment: Horizontal_Positional_Accuracy_Value: 60 meters Horizontal_Positional_Accuracy_Explanation: 60 meters corresponds to 2 raster cells. An accuracy of less than 60 meters, or 2 cell sizes, is observed for all visually recognizable data points that can be used to compare the IKONOS imagery to the DEM-derived contour data. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: Although the vertical data cannot be directly derived from this TIFF data, this vertical positional accuracy report was written to qualify the resulting shade effect that has been derived from a conversion between vertical value and RGB hillshade value. After an assessment of the horizontal accuracy was complete, it was then possible to assess the vertical accuracy (see Horizontal_Positional_Accuracy_Report). Thirty-five sub-meter horizontal/vertical accuracy GPS points that were acquired during the summer field season 2000 and 2001 were used to assess the vertical accuracy. A calculation of the known GPS vertical value minus the SRTM DEM vertical value for the same horizontal position showed that the SRTM vertical data was under-estimating the elevation by 19.3 +/- 4.3 meters (mean and standard deviation of the 35 points reported). Twenty-nine GPS points were used in the same way to assess the vertical accuracy of the AirSAR DEM data. The results of the GPS minus AirSAR vertical values for the same horizontal point (after the X-Y shift was applied) are -0.3 +/- 5.44 (mean and standard deviation reported for 29 points). In conclusion, the vertical values for the SRTM DEM data set overestimate the true vertical value by about 19 meters, and the AirSAR DEM data vertical values are accurate to about 5 meters. Prior to creating the shaded relief image, these two data sets were combined by filling in any holes of the SRTM data with the AirSAR data. The bulk of the data used to derive the shaded relief image came from the SRTM data, and therefore the vertical accuracy for the values used to create the shaded relief image are taken to be about 19 meters. This agrees well with the NASA reported error for the data set which is 20 meters. Lineage: Source_Information: Source_Citation: Citation_Information: Originator: NASA Jet Propulsion Laboratory (JPL) and the National Geospatial-Intelligence Agency Publication_Date: 2003 Title: Shuttle Radar Topography Mission (SRTM) DEM data, files N53W168.hdr and N53W169.hdr Edition: ftp edition Geospatial_Data_Presentation_Form: raster digital data Series_Information: Series_Name: Initial release Issue_Identification: 2003 Publication_Information: Publication_Place: unknown Publisher: U.S. Geological Survey Other_Citation_Details: 2 digital files Online_Linkage: ftp://edcsgs9.cr.usgs.gov/pub/data/srtm/United_States_1arcsec/1arcsec/ Type_of_Source_Media: on-line Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 20000212 Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: NASA SRTM DEM, 2003 Source_Contribution: 1-arc second DEM data Source_Information: Source_Citation: Citation_Information: Originator: NASA Jet Propulsion Laboratory (JPL) and the Alaska SAR Facility (ASF) Publication_Date: 2001 Title: AirSAR DEM data for Okmok Volcano Edition: September 2001 Geospatial_Data_Presentation_Form: raster digital data Series_Information: Series_Name: Initial release Issue_Identification: September 2001 Publication_Information: Publication_Place: Fairbanks, AK Publisher: Alaska SAR Facility Other_Citation_Details: 1 CD Online_Linkage: NONE Type_of_Source_Media: CD Source_Time_Period_of_Content: Time_Period_Information: Single_Date/Time: Calendar_Date: 200009 Source_Currentness_Reference: ground condition Source_Citation_Abbreviation: AirSAR DEM, 2001 Source_Contribution: 5-meter DEM data Process_Step: Process_Description: Process Step 1 - Convert SRTM DEM data to ArcGRID Two SRTM DEM data sets were downloaded in May 2003 from the ftp site ftp://edcsgs9.cr.usgs.gov/pub/data/srtm/United_States_1arcsec/1arcsec/ Files N53W168.hdr.zip and N53W169.hdr.zip 1. Unzip SRTM DEM data file unzip FILENAME.hgt.zip 2. Rename using lower case letters mv FILENAME.hgt filename.bil 3. Make a hdr text file with the same name as the filename.bil, but call it filename.hdr for example, below is a header file called n53w167.hdr BYTEORDER M LAYOUT BIL NROWS 3601 NCOLS 3601 NBANDS 1 NBITS 16 BANDROWBYTES 7202 TOTALROWBYTES 7202 BANDGAPBYTES 0 NODATA -32768 ULXMAP -167.0 ULYMAP 54.0 XDIM 0.000277777777777 YDIM 0.000277777777777 Note that the SRTM naming convention specifies the lower left corner coordinates, while the hdr file needs the upper left coordinates (ULXMAP, ULYMAP). The variables ULXMAP and ULYMAP are the only two variables that will change with each new hdr file. 4. Create a grid using the arc command imagegrid Arc: imagegrid filename.bil filename IMAGEGRID does not support conversion of signed image data, therefore the negative 16-bit DEM values will not be interpreted correctly. After running IMAGEGRID, an easy fix can be accomplished using the following formula in Grid: out_grid = con(in_grid >= 32768, in_grid - 65536, in_grid) The converted grid will then have the negative values properly represented, and the statistics of the grid should match those listed in the .ANN file. 5. Repeat steps 1 through 4 for both SRTM DEM data files. 6. Merge the two data files in Arc Grid Grid: out_grid = merge(grid1, grid2) 7. Using Project wizard in ArcToolbox, reproject the merged grid from GCS WGS84 to Transverse Mercator, Zone 2, choosing a cell size of 30 meters. Source_Used_Citation_Abbreviation: NASA SRTM DEM, 2003 Process_Date: 2004 Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Janet R. Schaefer Contact_Organization: State of Alaska, Division of Geological & Geophysical Surveys Contact_Position: Alaska Volcano Observatory Geologist III Contact_Address: Address_Type: mailing and physical address Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907) 451-5010 Contact_TDD/TTY_Telephone: Not Available Contact_Facsimile_Telephone: (907) 451-5050 Contact_Electronic_Mail_Address: dggspubs@dnr.state.ak.us Hours_of_Service: 8 am to 5 pm, Monday through Friday, except State holidays Contact_Instructions: Please address all comments or questions to the e-mail address above whenever possible. Process_Step: Process_Description: Process Step 2 - Convert AirSAR DEM to Arc Grid. (1) AirSAR data were delivered to DGGS from the Alaska SAR Facility (ASF) in September 2001 in a geoTIFF format. (2) GeoTIFF was converted to an Arc grid using IMAGEGRID function in Arc. (3) Created a 10m contour map of the Arc grid and overlayed contour lines onto IKONOS imagery to determine horizontal accuracy (see Horizontal_Positional_Accuracy_Report). (4) Determined new values for xmin and ymin based on results discussed in Horizontal_Positional_Accuracy_Report. Applied shift to AirSAR DEM Arc Grid using the following command in Arc Grid newgrid = shift(oldgrid, newxmin, newymin). Source_Used_Citation_Abbreviation: AirSAR DEM, 2001 Process_Date: 2004 Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Janet R. Schaefer Contact_Organization: State of Alaska, Division of Geological & Geophysical Surveys Contact_Position: Alaska Volcano Observatory Geologist III Contact_Address: Address_Type: mailing and physical address Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907) 451-5010 Contact_TDD/TTY_Telephone: Not Available Contact_Facsimile_Telephone: (907) 451-5050 Contact_Electronic_Mail_Address: dggspubs@dnr.state.ak.us Hours_of_Service: 8 am to 5 pm, Monday through Friday, except State holidays Contact_Instructions: Please address all comments or questions to the e-mail address above whenever possible. Process_Step: Process_Description: Process Step 3 - Merge the AirSAR and SRTM DEMs and create a georeferenced shaded relief TIFF. (1) Merge the horizontally corrected AirSAR Arc grid with the SRTM Dem Arc Grid in Arc Grid by replacing all SRTM DEM values less than zero with the AirSAR DEM value. Grid: newgrid = con(srtmdemgrid < 0, airsardem, srtmdemgrid). (2)In ArcMap 8.2, create a hillshade with 2x vertical exaggeration using 3D-Analyst extension. (3)Convert the resulting hillshaded grid into a TIFF using the Arc command GRIDIMAGE. Grid: GRIDIMAGE in_grid NONE out_image TIFF. (4)In ArcMap 8.2, georeference the image to UTM Zone 2, WGS 84, by adding corner control points. RMS error = 0. Update georeferencing, then rectify using bilinear interpretation. Process_Date: 2004 Process_Contact: Contact_Information: Contact_Person_Primary: Contact_Person: Janet R. Schaefer Contact_Organization: State of Alaska, Division of Geological & Geophysical Surveys Contact_Position: Alaska Volcano Observatory Geologist III Contact_Address: Address_Type: mailing and physical address Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907) 451-5010 Contact_TDD/TTY_Telephone: Not Available Contact_Facsimile_Telephone: (907) 451-5050 Contact_Electronic_Mail_Address: dggspubs@dnr.state.ak.us Hours_of_Service: 8 am to 5 pm, Monday through Friday, except State holidays Contact_Instructions: Please address all comments or questions to the e-mail address above whenever possible. Cloud_Cover: unknown Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: Raster Raster_Object_Information: Raster_Object_Type: Pixel Row_Count: 3894 Column_Count: 4577 Vertical_Count: 1 Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 2 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.9996 Longitude_of_Central_Meridian: -171.0000 Latitude_of_Projection_Origin: 0.0000 False_Easting: 500000.0000 False_Northing: 0.0000 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: row and column Coordinate_Representation: Abscissa_Resolution: 30.003283 Ordinate_Resolution: 30.003283 Planar_Distance_Units: meters Geodetic_Model: Horizontal_Datum_Name: WGS 1984 Ellipsoid_Name: WGS 1984 Semi-major_Axis: 6378137.0000 Denominator_of_Flattening_Ratio: 298.257224 Metadata_Reference_Information: Metadata_Date: 20050112 Metadata_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: State of Alaska, Division of Geological & Geophysical Surveys Contact_Person: Janet R. Schaefer Contact_Position: Alaska Volcano Observatory Geologist III Contact_Address: Address_Type: mailing and physical address Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907) 451-5010 Contact_TDD/TTY_Telephone: Not Available Contact_Facsimile_Telephone: (907) 451-5050 Contact_Electronic_Mail_Address: dggspubs@dnr.state.ak.us Hours_of_Service: 8 am to 5 pm, Monday through Friday, except State holidays Contact_Instructions: Please address all comments or questions to the e-mail address above whenever possible. Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Access_Constraints: none Metadata_Use_Constraints: If the user has modified the data in any way they are obligated to describe the types of modifications they have performed in the supporting metadata file. User specifically agrees not to imply that changes they made were approved by the Alaska Department of Natural Resources or Division of Geological & Geophysical Surveys.