Download Data

Arc/Info Export Files

There are two ARC/INFO export files (.e00) availablefor the Hilo survey on this CD-ROM;

1. Bathymetry - Depth


2. Backscatter - Digital number (DN) associated with the reflected energyoff the seafloor


Full Resolution TIFF Images

There are three full resolution TIFF images availablefor the Hilo survey on this CD-ROM.

These files can be added to a GIS system by creatinga world file using the information from the Arc/Info Grid Information below.

Or these files can be directly opened in many imageprocessing programs such as Adobe Photoshop and Adobe Illustrator.

1. bi_shd.tif.gz: Shaded relief of bathymetry using 50degree azimuth and altitude of 45 degress.

2. bi_bathy.tif.gz : Bathymetry

3. bi_back.tif.gz: Backscatter

Formal Metadata

Download Instructions

1. Download compressed ARC/INFO export and TIFFfiles into drive and/or folder.

2. Uncompress files using decompression program.There are different decompressing programs for specific computer platforms.

 - UNIX usually has a version of GZIP alreadyunstalled on the system. If not, there are four of the more common GZIPprograms on this CD-ROM (Alpha Dec, SGI, Sparc-Solaris 2.5 and 2.6). Thesecan be found in the top directory of this CD-ROM in the GZIP folder underUNIX. If you are on a different system go to to findthe GZIP program that will work for you.

- Window users may use Winzip to decompressthese files. There is also a freeware Windows version of GZIP on this CD-ROM.This can be found in the top directory of this CD-ROM in the GZIP folderunder Windows.

-Macintosh users may use MacGZIP. There is a copy on this CD-ROM. Thiscan be found in the top directory of this CD-ROM in the GZIP folder underMac.

3 "Import" the Arc/Info export filesusing the grid option.

Data Collection

Mapping offshore of Hilo, Hawai was done in February1998 using a Kongsberg Simrad EM-300 Multibeam System hull mounted to C&CTechnologies' RV Ocean Alert.

Processing Steps

1. Bathymetry and backscatter data processed onSilicon Graphic computer using software developed by the Ocean Mapping Group,University of New Brunswick. (see USGS OpenFile Report 98-509, The Bathymetry of Lake Tahoe, California-Nevada)
2. Processed data downloaded to a Sun Sparc Ultra 2, running Solaris 2.5as an ascii file (longitude, latitude, depth, or backscatter DN value)
3. In Arc/Info 7.1.2 a point coverage is created from the ascii file.
4. Point coverge is projected from Geographic Coordinate System to UTM projection.
5. Projected point coverage is gridded using IDW (Inverse Distance Weighted)function.
6a. Grid is exported to Arc/Info export (.e00) file.
6b. Grid is converted to a TIFF image using the "Gridimage" command.
7. Both the export and TIFF files are compressed using UNIX version of GZIP.

Arc/Info Grid Information


 Cell Size = 8.000
 Data Type: Floating Point
 Number of Rows= 4611
 Number of Columns = 3762
 Xmin = 281565.344
 Xmax = 311661.344
 Ymin = 2176377.750
 Ymax = 2213265.750
 Minimum Value = -3376.310
 Maximum Value =-24.123
 Mean = -1159.670
 Standard Deviation = 808.246
 Projection UTM
 Zone 5
 Datum WGS84
 Spheroid WGS84


 Cell Size = 8.000
 Data Type: Floating Point
 Number of Rows= 4587
 Number of Columns = 3766
 Xmin = 281558.375
 Xmax = 311686.375
 Ymin = 2176380.500
 Ymax = 2213076.500
 Minimum Value = 31.978
 Maximum Value =251.474
 Mean = 181.905
 Standard Deviation = 13.305
 Projection UTM
 Zone 5
 Datum WGS84
 Spheroid WGS84

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