J. LaRue Smith 2008 raster digital data Reston, VA U.S. Geological Survey http://water.usgs.gov/lookup/getspatial?sir2007-5012_bathymetry Lopes, T.J. Smith, J.L. 2007 document Scientific Investigation Report 2007-5012 Reston, VA U.S. Geological Survey http://pubs.usgs.gov/sir/2007/5012/pdf/sir20075012.pdf http://pubs.usgs.gov/sir/2007/5012/pdf/sir20075012_plate1.pdf Walker Lake lies within a topographically closed basin in west-central Nevada and is the terminus of the Walker River. Accurately determining the bathymetry and relations between lake-surface altitude, surface area, and storage volume are part of a study to improve the water budget for Walker Lake. Bathymetry of Walker Lake was measured using a single-beam echosounder coupled to a differentially-corrected global positioning system. Lake depth was subtracted from the lake-surface altitude to calculate the altitude of the lake bottom. A Lidar (light detection and ranging) survey and high resolution aerial imagery were used to create digital elevation models (DEM) around Walker Lake. All data was aquired during 2005. The altitude of the lake bottom and DEMs were merged together to create a single DEM and was used to identify areas that are currently or that were submerged by Walker Lake. The data sets and the procedures used to create the DEM are described in this metadata. The DEM described and documented was used to make comparisons of relations between lake-surface altitude, surface area, and storage volume from the Walker Lake study and Rush (1970); and an estimate of the 1882 lake-surface altitude. This data set was created as part of a U.S. Geological Survey (USGS) study, done in cooperation with the Bureau of Land Management. The intended uses of this data set include, but are not limited to, natural resource modeling, mapping, and visualization applications. The USGS and the National Aeronautics and Space Administration (NASA), shared research involving USGS hydrologic studies of evapotranspiration and surface-water modeling and NASA development of the Experimental Advanced Airborne Research Lidar (EAARL) system. For information of the EAARL system see Nayegandhi and others (2006). Parameters of the Lidar data are as follows. The ground post spacing was 2.5 m and about 2 m along the flight path. No overlap of flight lines was done. The footprint of the Lidar on the ground is about 15 cm. The sampling interval of the Lidar is 1 nanosecond which translates to about 15 cm vertical resolution. Post-flight processing of EAARL data is accomplished using a custom-built processing system known as the Airborne Lidar Processing System (ALPS). The ALPS software has been developed in a collaboration between NASA and USGS in an open-source programming environment on a Linux platform. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. Specialized filtering algorithms have been implemented to determine the 'bare Earth' under vegetation from a point cloud of 'last return' elevations. No editing of the resulting data was done. The data set is not a true bare earth. Buildings and trees still remain in the data set. The elevation derived from the high resolution imagery is an automated procedure and does not produce a true bare-earth DEM. Nayegandhi, A., Brock, J.C., Wright, C.W., and O'Connell, M., 2006, Evaluating small-footprint waveform-resolving lidar over coastal vegetated communities: Journal of Photogrammetric Engineering and Remote Sensing Forestry Lidar Special Issue, v. 72, no. 12, p. 1407-1417. 2005 ground condition Complete None planned -119.258419 -118.306393 39.383018 38.365568 None. bathymetry digital elevation model Lidar sonar inlandWaters elevation climateMeterologyAtmosphere None. Walker Lake central Nevada Mineral County Churchill County None. Restrictions and legal prerequisites for using the data set after access is granted. Acknowledgment of the U.S. Geological Survey and Bureau of Reclamation would be appreciated in products derived from these data. Although this Federal Geographic Data Committee (FGDC) compliant metadata file is intended to document the data set in nonproprietary form, this metadata file may include some ArcGIS-specific terminology. These data are not intended to be used as a survey product and are for reference only. U.S. Geological Survey Nevada Water Science Center Public Information Officer Mailing and physical address

2730 N. Deer Run Road

Carson City NV 89701 USA (775) 887-7600 (775) 887-7629 Compilation of this data set and the associated metadata was done in cooperation with the Bureau of Reclamation. Technical review of this database was done by Wesley E. Newton and Nancy A. Damar of the U.S. Geological Survey. Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 9.2.6.1500 Rush, F.E. 1970 atlas Hydrologic Investigations Atlas HA-415 Reston, VA U.S. Geological Survey http://pubs.er.usgs.gov/usgspubs/ha/ha415 Throughout the processing tests of valid values were determined. All areas were completely described. No inconsistencies were determined. Complete. The digital surface model (DSM) has a horizontal positional accuracy of about .3696 m. The Lidar data has a horizontal positional accuracy of about 1 meter. The single beam sonar horizontal positional accuracy is unknown. The DSM vertical accuracy is unknown. The Lidar data has a vertical accuracy of 13 to 20 cm. The single beam sonar has a vertical accuracy of 1 cm. EarthData International, LLC Unpublished Material disc 20050628 publication date DSM Generally, elevation values in the mountains National Aeronautics and Space Administration Unpublished Material disc 20050525 20050602 ground condition Lidar Generally, elevations in the valley U.S. Geological Survey Unpublished Material 2.7-degree beam width and 200 kilohertz disc 20050201 20050431 ground condition sonar The bathymetric measurements of Walker Lake Bathymetric data were collected over the navigable areas of Walker Lake using an automated system consisting of a single-beam echosounder (fathometer) coupled to a real-time, differentially-corrected global positioning system (GPS). Survey lines were spaced 500 m in the east-west direction and 1000 m in the north-south direction. Raw data were processed in Hypack Max software and exported in a latitude, longitude, and depth format for importing into the geographic information system (GIS) ArcGIS for additional processing. From the high resolution imagery the lake boundary was digitized. An altitude of 1199.56 m was assigned to the lake boundary. The lake-bottom altitude, altitude of the lake boundary, and altitude of selected near-shore points were used in the ArcGIS kriging module to interpolate lake-bottom altitudes between data points. The ordinary kriging method was used with a spherical semi-variogram model, variable search radius, and a minimum of twelve data points to interpolate values for 5 m cells. sonar 2005 sonar The basic Lidar data was processed by NASA. Post-flight processing of Lidar data were done using NASA's Airborne Lidar Processing System (ALPS) by the USGS. Removal of invalid data along the mountain areas was done as well as selected flight lines along the Walker River and around Walker Lake because of problems with the sensor. Random consensus filtering and removal of anomalous data was performed to determine bare-earth values. All flights of data were merged. A Digital Elevation Model (DEM) was created using ArcGIS software. The latitude, longitude, and altitude points were used to produce a 2 m cell size raster surface. The inverse distance weighted algorithm was used to create the surface and required two points to determine the cell value. If 2 points were not within 5 m of the cell, no value was determined. Lidar 2005 Lidar High resolution imagery was collected in the Walker Lake area by EarthData International, LLC,. Ortho-rectification processing of the imagery was performed using various programs in the ISTAR system by EarthData International, LLC. Using several tools that are part of the ISTAR workflow, a DEM was correlated at a post spacing of 4 m depending on terrain and land cover. DSM 2005 DSM Merging of all data into a mosaic was performed. Lidar and DSM data were merged. Where do data of Lidar was collected, the DSM was used. A value of 1 m was subtracted from the DSM before merging. It is unknown why, but was determined by examining level areas where the two data sets where merged. Sonar data was inserted into the merged Lidar and DSM. A value of 24.9 m was subtracted from the sonar data first to convert from NAVD 88 to WGS84 vertical datum, then was merged with the other data. Cell size was resampled to 5 m. sonar Lidar DSM 2005 Raster Grid Cell 22279 16089 1 Universal Transverse Mercator 11 0.999600 -117.000000 0.000000 500000.000000 0.000000 row and column 5.000000 5.000000 meters North American Datum of 1983 Geodetic Reference System 80 6378137.000000 298.257222 World Geodetic System of 1984 (WGS 84) .001 m meters Attribute values Chart datum; datum for sounding reduction .001 m meters Attribute values Value The digital elevation value. Lidar, digital surface model, and sonar soundings There is no attribute table created. The values are elevation above sea level in meters. NODATA values do exist. None. U.S. Geological Survey Ask USGS -- Water Webserver Team mailing address

507 National Center

Reston VA 20192 USA 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov Downloadable Data Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data and related materials. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of these data, software, or related materials. The use of firm, trade, or brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. The names mentioned in this document may be trademarks or registered trademarks of their respective trademark owners. ArcGIS grid 2008 Spatial and attribute information WinZip 9.0 534.438 megs http://water.usgs.gov/GIS/dsdl/sir2007-5012_bathymetry.zip BIL 2008 Spatial and attribute information WinZip 9.0 338.041 megs http://water.usgs.gov/GIS/dsdl/sir2007-5012_bathymetry2.zip To obtain altitude divide by 100 None 20090113 U.S. Geological Survey J. LaRue Smith Hydrologist mailing address

445 National Center

Reston VA 20192 USA 1-888-275-8747 (1-888-ASK-USGS) http://answers.usgs.gov/cgi-bin/gsanswers?pemail=h2oteam&subject=GIS+Dataset+sir20075012_bathymetry FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time http://www.esri.com/metadata/esriprof80.html ESRI Metadata Profile