From Ocean Teacher Library

Auxiliary Formats

Contents 1 Background 2 Index Files 3 Header Files 3.1 CTL Header for GRADS Program 3.2 DGM Header for Saga Grids 3.3 HDR File for ESRI GIS Data Grids 3.4 HDR for Seabird CTD Spreadsheets 3.5 World Files for GIS Images 3.6 XIMG Files for Images in IDV 3.7 KML Files used for Georeferencing Images 3.8 Projection Files for ESRI Shapefiles 3.9 GRIB Map Files (GMP) 4 Palette Files 4.1 Saga Palettes 4.2 Ocean Data View Palettes 5 Project Files 5.1 ArcExplorer Projects (AXL) 5.2 KML used as a Project File 5.3 Saga Projects (SPRJ) 5.4 Surfer Projects (SRF) 6 Additional Resources 7 Subsections of this Article 8 Information about this article 9 Contact

Background

Files created purely for functional purposes, containing no data, but written to assist executable programs find or use data files.

• Advantages
  • Easily edited ASCII.
  • Facilitate rapid data use within certain programs, as opposed to repetitive manual entry of descriptive information.
• Disadvantages
  • Can become separated from the main data file or folder structure they describe. Can become useless in the event of any filename or folder name change.
  • Compatibilities Usually designed to be compatible with specific software programs which "look" for them when a main data file is opened. Even when they are not compatible with other programs, the user can examine them visually to obtain necessary information.

Index Files

• Contain a list of all files in a folder or on a physical volume. Automatically created.
• Contain a list of all files to be included in a batch processing job. Manually created.

Header Files

Helper files containing format information about other data-containing files, or actual headers inserted at the beginning of some other format types. For example, all Document Formats contain headers to assist the reader in understanding the source and contents of the data. The difference between Header file formats and Metadata file formats is not sharp; Header formats tend to be quite small, ad-hoc constructions, designed just to impart essential data format information. Metadata files are never inserted into data files, and they tend to be lengthy (although this is not a consistent criterion).

CTL Header for GRADS Program

This file indicates to the GRADS program how to read the data in a GRIB formatted datafile. GRIB files contain multi-dimensional grids of environmental data, and the exact order must be specified here for reading the grid layers and their parameters. Included here due to the almost universal use of GRADS by meteorologists and climatologists.

• Example:

DSET data/biosphere/czcs_color/climate/czcs.chlrcn.1nxego.bin
UNDEF -99.
OPTIONS yrev
OPTIONS template
OPTIONS big_endian
TITLE chlorophyll (pigment) concentration
XDEF 360 LINEAR -179.5 1.0
YDEF 180 LINEAR -89.5 1.0
ZDEF 1 LINEAR 0.0 0.0
TDEF   1 LINEAR JAN1900 1mo
VARS 1
chlrcn  0  99  chlorophyll (pigment) concentration
ENDVARS

DGM Header for Saga Grids

Very typical georeferencing information for Saga's native gridded data format.

• Example:

NAME= NamibiaSummerTemp400m.txt (Inverse Distance)
DESCRIPTION= 
UNIT= 
DATAFILE_OFFSET= 0
DATAFORMAT= FLOAT
BYTEORDER_BIG= FALSE
POSITION_XMIN= -1.000000
POSITION_YMIN= -33.000000
CELLCOUNT_X= 22
CELLCOUNT_Y= 21
CELLSIZE= 1.000000
Z_FACTOR= 1.000000
NODATA_VALUE= -99999.000000
TOPTOBOTTOM= FALSE

HDR File for ESRI GIS Data Grids

This type of header can be a stand-alone *.HDR file for a binary gridded datafile (usually named *.FLT), or it can be the first six lines in an ASCII gridded datafile (*.ASC or *.TXT). The specification for this header is given below.

• Example:

NCOLS 22
NROWS 21
XLLCENTER -1.000000
YLLCENTER -33.000000
CELLSIZE 1.000000
NODATA_VALUE -99999.000000

IMPORTANT NOTE: The 3rd and 4th lines can be XLLCORNER and YLLCORNER, in a common variant of the format, referring to properties of the lower left cell (i.e. center or edge of the cell).

• Files available: For easy reference, these HDR examples are listed with their FLT files at Raster and Grid Formats

HDR for Seabird CTD Spreadsheets

Seabird CTD data can be contained in separate data (*.ASC) and header (*.HDR) files, or combined in a single *.CNV) file.

• Example:

Sea-Bird SBE 19plus Data File:
FileName = C:\Sea-Bird\Casts\050524_130.hex
Software Version Seasave Win32 V 5.31a
Temperature SN = 4126
Conductivity SN = 4126
System UpLoad Time = May 24 2005 08:21:57
Ship:       
Cruise:     
Station:    
Latitude:   
Longitude:  
nquan = 12
nvalues = 17                          
units = specified
name 0 = prdM: Pressure, Strain Gauge [db]
name 1 = tv290C: Temperature [ITS-90, deg C]
name 2 = c0mS/cm: Conductivity [mS/cm]
name 3 = obs: OBS, Backscatterance (D + A) [NTU]
name 4 = par: PAR/Irradiance, Biospherical/Licor
name 5 = spar: SPAR/Surface Irradiance
name 6 = cpar: CPAR/Corrected Irradiance [%]
name 7 = depSM: Depth [salt water, m]
name 8 = nbin: number of scans per bin
name 9 = sal00: Salinity [PSU]
name 10 = density00: Density [density, Kg/m^3]
name 11 = flag: flag
span 0 =      1.009,      9.079       
span 1 =    12.6686,    13.0429       
span 2 =  33.994061,  36.765508       
span 3 =    24.6481,   645.1685       
span 4 = 9.2177e-01, 1.3836e+02       
span 5 = 1.0575e+05, 1.0575e+05       
span 6 = 2.9530e-01, 4.4993e+01       
span 7 =      1.000,      9.000       
span 8 =          4,          9       
span 9 =    28.4094,    31.1063       
span 10 =  1021.2899,  1023.4230      
span 11 = 0.0000e+00, 0.0000e+00      
interval = meters: 1                  
start_time = May 24 2005 08:21:57
bad_flag = -9.990e-29
sensor 0 = Frequency 0  temperature, 4126, 12-May-04
sensor 1 = Frequency 1  conductivity, 4126, 12-May-04, cpcor = -9.5700e-08
sensor 2 = Pressure Number
sensor 3 = Extrnl Volt  0  backscatterance, 1814, 07-May-04
sensor 4 = Extrnl Volt  1  irradiance (PAR), primary, 20141, 16/09/04
sensor 5 = Extrnl Volt  3  surface irradiance (SPAR), degrees = 0.0
datcnv_date = Aug 01 2005 12:48:36, 5.32a
datcnv_in = \\Fms\shared\ship\ctdcasts\processing\sbe19plus-4126-0410\4126_050524_130.hex \\Fms\shared\ship\ctdcasts\processing\sbe19plus-4126-0410\4126_0410.con
datcnv_skipover = 0
filter_date = Aug 01 2005 13:49:16, 5.32a
filter_in = \\Fms\shared\ship\ctdcasts\processing\sbe19plus-4126-0410\cnv\4126_050524_130_C.cnv
filter_low_pass_tc_A = 0.500
filter_low_pass_tc_B = 1.000
filter_low_pass_A_vars = tv290C c0mS/cm obs
filter_low_pass_B_vars = prdM depSM
alignctd_date = Aug 01 2005 13:58:32, 5.32a
alignctd_in = \\Fms\shared\ship\ctdcasts\processing\sbe19plus-4126-0410\cnv\filter\4126_050524_130_CF.cnv
alignctd_adv = tv290C 0.500
loopedit_date = Aug 01 2005 14:03:51, 5.32a
loopedit_in = \\Fms\shared\ship\ctdcasts\processing\sbe19plus-4126-0410\cnv\filter\align\4126_050524_130_CFA.cnv
loopedit_minVelocity = 0.250                                                         
loopedit_excl_bad_scans = yes
binavg_date = Aug 01 2005 14:10:25, 5.32a
binavg_in = \\Fms\shared\ship\ctdcasts\processing\sbe19plus-4126-0410\cnv\filter\align\loop\4126_050524_130_CFAL.cnv
binavg_bintype = meters
binavg_binsize = 1
binavg_excl_bad_scans = yes
binavg_skipover = 0
binavg_surface_bin = no, min = 0.000, max = 0.000, value = 0.000
Derive_date = Aug 01 2005 14:20:18, 5.32a
Derive_in = \\Fms\shared\ship\ctdcasts\processing\sbe19plus-4126-0410\cnv\filter\align\loop\bin\4126_050524_130_CFALB.cnv \\Fms\shared\ship\ctdcasts\processing\sbe19plus-4126-0410\4126_0410.con
file_type = ascii
END

World Files for GIS Images

World files indicate to GIS programs how images can be mapped onto the earth's surface. World files "match up" with their image files by using the same filename with a slightly different extension. JPG, TIF, GIF, BMP, PNG, etc. images, would have the filename extensions JPW, TFW, GFW, BPW, PGW, etc. The specification for writing a world file is given below.

• Example:

0.28125
0
0
-0.28125
-179.859375
89.859375

In order, these values represent:

• Delta-X = column spacing = east-west size of each pixel in map units
• Rotation of the image in relation to the ordinate (y axis)
• Rotation of the image in relation to the abscissa (x axis)
• Delta-Y = row spacing = north-south size of each pixel in map units
• X coordinate of the center of the north-west corner pixel
• Y coordinate of the center of the north-west corner pixel

Note that the last two items indicate that World Files use the cell-centered convention so the image is 1/2 grid cell larger on all sides than the X and Y coordinates, shown above, might indicate.

Note that the Delta-Y is always negative, because the successive rows of the grid move southward. Note also that the image is "anchored" by X and Y values of the northwest corner, and this is the location of the first data value in the file. ESRI ASCII grids, on the other hand, are anchored at the southwest corner, but the data values begin in the northwest corner also.

XIMG Files for Images in IDV

Similar to world files in form and usage. Use these as the target file in IDV instead of the image proper.

• Example

<image name="Canary Area Buoy Trajectories"
url="currents_canary_all_gdp_saga.png"
ullat="9"
ullon="-23"
lrlat="-6"
lrlon="-3"/>

KML Files used for Georeferencing Images

• Google's Keyhole Markup Language (KML) can also be used to georeference images. This example is for an image named test_region.png that covers the area offshore Namibia:

<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.0">
<GroundOverlay>
 <name>test_region</name>
 <Icon><href>test_region.png</href></Icon>
 <LatLonBox>
  <west>3.0</west>
  <north>-13.0</north>
  <east>26.0</east>
  <south>-33.0</south>
 </LatLonBox>
</GroundOverlay>
</kml>

• KML files used for georeferencing use the vertex-centered convention, so the limits shown above are the actual edges of the image.
• A KML file and all of its local images can be compressed into the ZIP format, and given the extension KMZ. To unzip the file, simply change the extension back to ZIP and use nearly any uncompression utility.

Projection Files for ESRI Shapefiles

The suite of files that together is often called a "shape" or shapefile in ESRI software includes several types that can be called auxiliary. Shown here is the most obvious auxiliary type, the projection file (*.PRJ) that provides detailed geo-location information. Note that the original PRJ file contains one long string of items without any line breaks; this example has been broken into sections for ease in reading.

PROJCS["World_Mercator",
 GEOGCS["GCS_WGS_1984",
  DATUM["D_WGS_1984",
   SPHEROID["WGS_1984",6378137.0,298.257223563]],
  PRIMEM["Greenwich",0.0],
 UNIT["Degree",0.0174532925199433]],
 PROJECTION["Mercator"],
 PARAMETER["False_Easting",0.0],
 PARAMETER["False_Northing",0.0],
 PARAMETER["Standard_Parallel_1",0.0],
UNIT["Meter",1.0]]

GRIB Map Files (GMP)

• Binary

Palette Files

Files that specify the exact formula of red, blue and green components for a given color in a set of colors ("palette"). The three values can optionally be given as decimal fractions from 0.0 to 1.0, as integers from 0 to 255, or as percentages from 0% to 100%. Any given application can employ many palettes, each specified by name.

• Example:

(0, 0, 0) is black
(255, 255, 255) is white
(255, 0, 0) is red
(0, 255, 0) is green
(0, 0, 255) is blue
(255, 255, 0) is yellow
(0, 255, 255) is cyan
(255, 0, 255) is magenta

Saga Palettes

• Binary

Ocean Data View Palettes

First 15 colors in one of ODVs large set of palettes:

 0  0.000  0.000  0.000
 1  0.000  0.000  1.000
 2  0.000  0.700  0.000
 3  0.000  0.600  0.600
 4  0.800  0.000  0.000
 5  0.700  0.000  0.700
 6  0.659  0.471  0.282
 7  0.800  0.800  0.800
 8  0.500  0.500  0.500
 9  0.500  0.500  1.000
10  0.100  1.000  0.100
11  0.004  0.922  0.647
12  1.000  0.000  0.000
13  1.000  0.100  1.000
14  0.996  0.776  0.106
15  1.000  1.000  1.000
etc.

Project Files

Most GIS systems have the capability to store a list of the various data layers that have been combined into a named "project". This project can be recalled quickly at a later date by the use of this file. Different formats are used, often based now on XML.

ArcExplorer Projects (AXL)

These are "AXL" files developed by ESRI, using XML format. The resource file locations are hard-coded in these files, so moving any file can cause the project to be disrupted. [Notice that this AXL file actually specifies an image from a remote server.]

• Example:

<?xml version="1.0" encoding="UTF-8"?>
<ARCXML version="1.1">
 <CONFIG>
   <ENVIRONMENT>
     <LOCALE country="US" language="en" variant="" />
     <UIFONT color="0,0,0" name="SansSerif" size="12" style="regular" />
     <SCREEN dpi="96" />
   </ENVIRONMENT>
   <MAP>
     <PROPERTIES>
       <ENVELOPE minx="-2921118.0384015385" miny="-4094554.25045277" maxx="865277.1273420551" maxy="-1582532.6273988243" name="Initial_Extent" />
       <MAPUNITS units="meters" />
     </PROPERTIES>
     <WORKSPACES>
       <IMAGESERVERWORKSPACE name="mapper_ws-0" url="http://certmapper.cr.usgs.gov/servlet/com.esri.esrimap.Esrimap" service="WorldAfrica" />
     </WORKSPACES>
     <LAYER type="image" name="WorldAfrica" visible="true" id="0">
       <DATASET name="WorldAfrica" type="image" workspace="mapper_ws-0" />
     </LAYER>
   </MAP>
 </CONFIG>
</ARCXML>

KML used as a Project File

• Google's Keyhole Markup Language can be used to list images and shapes to be included in a single presentation. This is in addition to KML's use for georeferencing (see above) and for containing vector-type data.
• A KML file and all of its local images can be compressed into the ZIP format, and given the extension KMZ. To unzip the file, simply change the extension back to ZIP and use nearly any uncompression utility.

Saga Projects (SPRJ)

XML-formatted descriptions of the files selected to be displayed in a "project" along with palette information and other ancillary settings. Can be set to open automatically.

Surfer Projects (SRF)

• Project file format used by Surfer; large and binary

Additional Resources

• Wikipedia: World file
• Wikipedia: ESRI grid - Note that the ASCII part of this article is correct, but the binary part seems to be describing a different kind of ESRI file (i.e. the Arc/INFO grid)
• Google Earth KML Homepage - Includes extensive documentation, tutorials and examples.

Subsections of this Article

No subsections available

Information about this article

Short title: Auxiliary Formats

Description: Auxiliary formats are usually small files that contain instructions (or other information) that an executable program needs in order to use the data file. They are much less comprehensive than true metadata files, which can play similar roles

Expertise level: beginner

Author: Murray.Brown

Approval status: approved

Approved by: Murray.Brown

Last change: 2011-12-12

Subsection of: Marine Data Format Types

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