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GEODAS Icon GEODAS Grid Translator - Design-a-Grid help button

Windows    Macintosh    UNIX-LE (Linux-X86, etc.)    UNIX-BE (Sun, etc.)
(Create 8-char Identifier for Grid)
Upper Latitude
Left Longitude    
  
  Right Longitude
Lower Latitude
  
Number of Latitude Cells: Number of Longitude Cells:
Output Grid Format:
Binary Raster Format
ASCII Raster Format
XYZ (lon,lat,depth)
Output Grid Header:
GRD98 Header
ASCII (Arc) Header
No Header
GEODAS GEODAS ETOPO1 ETOPO1 Global Relief Coastal Relief Model US Coastal Relief Model Great Lakes Bathymetry Great Lakes Bathymetry
GEODAS Grid Translator Design-a-Grid - Custom grids from several GEODAS Gridded Databases can be created. Databases include: ETOPO2 Global Relief, US Coastal Relief Model and Great Lakes Bathymetry. Users choose the criteria for their custom grid, including lat/lon area, grid cell size, format, etc. The number of latitude and longitude cells of your grid will automatically be calculated and displayed. After setting options click Submit button to create the grid. Use option help icons for specific details about using the options. Use the Advanced Options button for options such as Output Number-type, setting the Empty Grid Cell value, setting Grid Radius value, creating only land or sea cells, etc. Resulting grid will have units of meters.
Your Operating System - The type of computer you are using is, in most cases, automatically determined. Change this only if you wish to output files to a format different from the one which was determined for you.

Grid Format Options - Choose from various grid formats and format options.

Binary Raster Format: Simply a continuous series of binary depth values. If you also choose the GRD98 Header, the header will be attached to the beginning of the output file and you will have the GEODAS Gridded Database Format GRD98. This format can later be opened in GEODAS Software Application Grid Translator and you can then create new custom grids with different lat/lon bounds, cell size, number type, etc. GRD98 grids can be viewed and edited in GEODAS Application Hydro-Plot. GRD98 grids can also be imported directly into GMT (Generic Mapping Tool) Version 4. If you choose the ASCII (Arc) Header, the header will be in a separate file with a file extention of .hdr. This combination (Binary Raster w/ Arc Header) can be opened in GEODAS Hydro-Plot. If you chose Floating Pt as your number type this combination can be imported into ArcGIS, and perhaps other GIS systems.

ASCII Raster Format: A row by row series of space-delimited ASCII depth values. Each row ends with an End-of-Line indicator. The EOL will be a Carriage-Return/Line-Feed (ASCII Decimal Character Codes 13 and 10) for MS Windows and a New-Line (ASCII Decimal Character Code 10) for UNIX and Macintosh. You cannot add a GRD98 Header to this format. If you add ASCII (Arc) Header, the header will be attached to the beginning of the output file, and this file can be imported directly into ArcGIS and perhaps other GIS systems, and can be viewed and edited in GEODAS Hydro-Plot.

XYZ (Delimited lon,lat,depth): Each grid value will be a separate record containing a lon, a lat and a depth, the records being terminated by a record delimiter (Carriage-Return/Line-Feed for Windows or New-Line for UNIX and Macintosh). The longitude, latitude and depth values are separated by field delimiters (see below). XYZ files can be viewed and edited in GEODAS Hydro-Plot and imported into various GIS systems. If you choose the ASCII (Arc) Header, the header will be in a separate file with a file extention of .hdr.

GRD98 Header: This is the header for creating binary raster GEODAS Gridded Database Format GRD98 grids.

ASCII (ArcGIS) Header: An ASCII grid header in the format used by Arc Systems. When used with the ASCII Raster Grid Format, the header file is attached to the beginning of the grid file. When used with Binary Raster Format and XYZ Format the header will be in a separate file with a file extention of .hdr.

No Header: No grid header will be associated with the grid data file. This is most often used with the XYZ (Delimited lon,lat,depth) Format.

XYZ Delimiter: For grid files of Delimited lon,lat,depth format only, choose space, tab or comma as the delimter to be inserted between the fields.

Omit Empty Grid Cells: For grid files of XYZ (Delimited lon,lat,depth) format you may include or omit the empty grid cell values in your output file. The default is to omit these values, which makes for easier importing into other applications.
Lat/Lon Area Bounds - Choose the latitude/longitude boundaries of your Search area in decimal degrees or in degrees, minutes and seconds. Switch between the 2 above methods with the button in the center of the lat/lon box. Latitudes must be between 90 degrees North and 90 degrees South. Longitude values must be between 180 degrees West and 180 degrees East (or -180 and +180). Your area may not cross both 0 degrees and 180 degrees (e.g. 120E to 120E will not work). If you wish your area to span the entire globe longitudinally, you should choose bounds of 180W to 180E (or -180 to +180), or just click the World button. This has the effect of not using area as a Search criteria. Use the Line or the Polygon(s) button to re-do your Search area as a (intersecting) line or as (multiple) polygons.
Grid Database - You must choose a GEODAS Gridded Database. This will be the source of the grid cells for your custom grid:

1. ETOPO2 Global Gridded Relief - Bathymetry and Elevation grids for the entire globe. Data is gridded at 2 minutes. Custom grids can be created by user.

2. US Coastal Relief Model - Bathymetric/Topographic grids at 3 arc-seconds for US coasts, created from the NOS Hydrographic Surveys database. Some sets are available now; more are in progress.

3. Great Lakes Bathymetry - Bathymetric/Topographic grids at 3 arc-seconds for the Great Lakes, created from the NOS Hydrographic Surveys database. Custom grids can now be created for all of the Great Lakes.
Grid Lat/Lon Area Bounds - Choose latitude/longitude bounds of your custom grid in degrees and minutes. Latitudes must be between 90 deg North and 90 deg South. Longitude values must be between 180 deg West and 180 deg East. Your grid may not cross both 0 deg and 180 deg. For grid to span the entire globe longitudinally (only relevent for ETOPO2 Global Relief), choose bounds of 180W to 180E, or from 0E to 0E. Depending on Grid Database and output Grid Cell Size, you may be restricted in your bounds. For example, if you have an output Grid Cell Size of 2 minutes, you may not choose a lat/lon minutes value of an odd number (e.g. 3 minutes).

Initial values for a particular Grid Database are outer bounds of that database. Extending bounds beyond that will result in the extra cells being filled with the Empty Grid Cell value (see Grid Cell Value Parameters).
Grid Cell Size - You may change the cell size of your custom grid from that of the source Grid Database. However, your cell size must be a mulitple of the source database cell size. Only acceptable cell sizes will be presented in the dialog. Be aware that cell size and area are related and certain combinations will not work. For example, if you chose a lat/lon bounds minutes value of an odd number (e.g. 3 minutes), you would not be able to have a cell size of 2 minutes. A warning will prompt you to change either lat/lon boundaries or cell size.
Grid Land/Sea Coverage - For US Coastal Relief Model only, Choose to transfer All Cells, Sea Cells Only, or Land Cells Only from the source Coastal Relief Model database. Un-transferred cells will contain the Empty Grid Cell Value.
Vertical Datum for Water Cells - Allows using local Great Lakes vertical datums for non-land cells. When using the default Mean Sea Level, water cells can have "depths" which are positive numbers. Using the Local Lake Datums will create grids with the proper water depths, but the land cells will still be based on acutal elevations (above mean sea level), thus showing a "cliff" where land starts.
Greenland/Antarctica Surface - This allows the user to create grid based on the current surface of the ice sheet in Greenland and Antarctica, or to base the grid on the bedrock (subtracting the ice thickness).
Grid Cell Parameters -

Number Type - Choose from 2-byte integers, 4-byte integers or 4-byte floating point (real) values. Note that this is only used by the binary raster grid format.
Precision - Grid values can be output with a precision of meters or tenths of meters. Note that the ETOPO2 Global database has source values of whole meters.
Empty Grid Cell Value - This is the value which will appear in the grid cells where there is no grid data from the source Grid Database. This is not relevant to the ETOPO2 Global database, since that database has values for all grid cells.
Grid Radius Value - This is only relevant to US Coastal Relief Model grids. This option can be used to discard grid data depending upon the proximity of the actual hydrographic data values. i.e. NGDC has used NOS Hydrographic Survey Data to create grid data values for the grid cells in each grid. Use a value of -1 if you do not wish the Grid Radius algorithm to be applied. But if you do not wish to use grid values where actual data was not in close proximity, you may apply the Grid Radius algorithm. If Grid Radius is set to zero or greater and the nearest actual data was more than Grid Radius grid cells away, the output cell will be given the Empty Grid Cell Value instead of the value contained in the Coastal Relief Model grid files. Note that Grid-Radius values are based on the Coastal Relief Model grid cell size (3 arc-seconds), not the output cell size.


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Website of the US Dept of Commerce/NOAA/NESDIS/NGDC, last update May 4, 2006
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