CoastWatch Data Analysis Tool Help: Exporting to other formats
In this section:
About exporting
Data may be exported to a variety of formats. Image formats
such as JPEG and PNG contain color pixel data computed by
converting data values to colors using the active enhancement and
palette. The output file contains an image similar to the
current data view. Data formats such as HDF and binary raster
contain one or more grids of 8-bit to 64-bit data values computed
directly from the source data. Select File|Export from the menu or click Export on the toolbar to export data.
Image formats
- PNG image
- A non-lossy compressed image format supported by most web
browsers and image manipulation software. PNG has similar data
compression characteristics to GIF and additionally supports 24-bit
color images.
- GIF image
- A non-lossy compressed format also supported by most web
browsers and image manipulation software. The GIF files produced
use LZW compression. Images stored in GIF format are run through a
color quantization algorithm to reduce the color map to 256 colors
or less. Although file sizes are generally smaller than PNG, image
quality may be compromised by the reduced color map.
- JPEG image
- A lossy compressed format that should be used with caution for
images with sharp color lines such as those found in text and
annotation graphics. The JPEG format generally achieves higher
compression than PNG or GIF resulting in smaller image file
sizes.
- GeoTIFF image
- A flexible image format with support for earth location
metadata. Many popular GIS packages handle GeoTIFF images and allow
the user to combine a GeoTIFF base map image with other sources of
raster and vector data. The GeoTIFF images generated are non-lossy
uncompressed image data (unless a compression is specified in the
options), and can be much larger than the corresponding PNG, GIF, or
JPEG. In general the GeoTIFFs generated are 24-bit colour images,
but when no overlays are used or the image color option is set, a
special 8-bit paletted image file is generated and comments
describing the data value scaling are inserting into the image
description tags.
- PDF document
- A standard document format for high quality publishing developed
by Adobe Systems and used for output to a printer via such tools as
the Adobe Acrobat Reader. In general, PDF files are slightly larger
than the equivalent PNG but retain highly accurate vector graphics
components such as lines and fonts.
Data formats
- CoastWatch HDF
- Hierarchical Data Format (HDF) version 4 with CoastWatch
metadata. HDF is a scientific data format used by CoastWatch and
others to distribute satellite data. Information and access
software may be found at http://hdf.ncsa.uiuc.edu. A description of
current CoastWatch metadata standards is available in the
CoastWatch Utilities user's guide.
- Binary raster
- A simple stream of binary data values -- either 8-bit unsigned
bytes, 16-bit signed integers, or 32-bit IEEE floating point values.
Data values may optionally be scaled to integers using the equation
integer = value/factor + offset. Each
data variable may be prepended with a 72-bit dimension header: 8-bit
dimension count (always 2) with 32-bit row count, 32-bit column
count.
- Text file
- An ASCII text file with latitude, longitude, and data value
printed -- one data value per line. Each data variable may be
prepended with a 1-line dimension header: dimension count (always
2), row count, column count.
- ArcGIS binary grid
- A stream of 32-bit IEEE floating point values, ready for input
to ESRI's ArcGIS as a binary grid file. A header file may also be
created to specify the earth location and other parameters.
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