Bathymetry and Acoustic Backscatter Data of Crater Lake, Oregon

The multibeam survey took place from July 28 to August 3, 2000 using a Kongsberg Simrad EM1002 Multibeam Sonar System. The system collects both bathymetry and co-registered, calibrated backscatter data. For more in-depth information about the survey and the EM1002 system see the USGS Open-File Report 00-405.

This CD-ROM contains both the bathymetry and acoustic backscatter data from the multibeam survey. The data are provided in two formats (ASCII XYZ and ArcInfo GRID) that can be used in a number of GIS and visualization software packages.

NOTE: The bathymetry data are published on this CD-ROM as elevations above sea level. The bathymetry data was converted from water depths to elevations using a lake level of 1882.6 m above sea level at the time of the multibeam survey. This was done because the lake level fluctuates seasonally and annually and also so the bathymetry data could be combined with USGS 10m or 30m 7.5 minute DEMs.

The data are available in ASCII XYZ (longitude, latitude, value) format. Click on either the bt_xyz.zip or bk_xyz.zip link below to download the data. The two files are compressed with WinZip 7.0.

Projection Information
Projection: Geographic
Datum: WGS84
Units: Decimal Degrees
Zunits: NO [backscatter]; Meters [bathymetry]
Spatial Resolution: 0.00002 degrees/pixel (2 meters in UTM, zone 10 coordinate system)

Federal Geographic Data Committee (FGDC) Metadata for XYZ format:
Text Format
HTML Format
FAQ format

The data are also available in ArcInfo GRID format that can be used directly in ArcInfo, ArcView, or any other GIS or remote sensing software package that supports ArcInfo GRID format. In ArcView, the GRID files will be most useful with the Spatial Analyst Extension.

Disclaimer: Downloading files from the Internet can sometimes be problematic. Different web browsers and operating systems act differently. The instructions below may vary from system to system or may not work at all.

One known problem is sometimes Netscape Navigator automatically changes the .tgz suffix to .tar during the download. If this happens change the .tar suffix back to .tgz after the download. Double click on the icon and Winzip should start up.

Download GRIDS to desktop

1. Click on each link below to download the files to the desktop.

2. Uncompress and unbundle the files. Since ESRI GRIDs are directories of files the directories have been bundled into a single file for downloading. Each bundled file is also compressed for faster downloading.

Windows - Double click on the file (bathy.tgz, backstr.tgz). Winzip 7.0 will uncompress the file resulting in a new bundled file (bathy.tar, backstr.tar). Double click on the new file and Winzip 7.0 will unbundle the file into a new folder (bathy, backstr). The ESRI GRID (bathyg, backstrg) is contained within the folder.

UNIX - Uncompress using "gunzip" then unbundle using "tar xf".

3. The bathymetry and acoustic backscatter GRID files (bathyg and mosg) are contained within each respective folder (bathy and mos).

Projection Information
Projection: UTM
Zone: 10
Datum: WGS84
Units: Meters
Zunits: NO [backscatter]; Meters [bathymetry]
Spatial Resolution: 2 meters

FGDC Metadata for ArcInfo GRID format:
Text Format
HTML Format
FAQ format