Frequently Asked Questions (FAQ)

Last update: February 2009

Installation

Windows: The software won't run because it is searching in non-existent directories

Linux/SUN Solaris: The Tcl/Tk HMI won't start

Linux/SUN Solaris: The dialogue boxes of the Tcl/Tk HMI are too big to fit on the screen

Import/Processing

All platforms: Handling of CEOS data with non standard filenames

All platforms: How to find Sub Swath Gain Parameters for the Enhancement Swath tool?

How to import ERS PGS CEOS data properly

RAW data (level 0)

Export

All platforms: Output TIFF/GeoTIFF/BIL files appear white

All platforms: How to import BIL files into image processing software

Installation

Windows: The software won’t run because it is searching in non-existent directories

The InstallShield package automatically sets three environment variables and the default destination folder ( C:\BESTv422-b). If the software is correctly installed, typing best in the DOS interface you should see the following message:

In some cases these can be corrupted, causing the software to look for directories in the wrong place (e.g. \BESTv422-b\bin\cfg or \BESTv422-b\bin\bin).

To solve the problem, reset the environment variables using the Set Environment Variables dialogue box in the HMI, as illustrated below

selecting \BESTv422-b as the root installation directory,

Restart the software after any changes.

Linux/SUN Solaris: The Tcl/Tk HMI won’t start (wish)

1. First verify that the BEST software itself is running correctly.

1.1. At the prompt, type the command:

best

You should see the following message:

BEST: Generic Tool ver. 4.2.2-b

2. Is Tcl/Tk installed on your machine?

2.1. The software can be downloaded from the Tcl Developer Xchange, where you will also find installation instructions.

3. If 1. and 2. are verified and you are still having problems starting the Tcl/Tk HMI, it may be because a Tcl interpreter called 'wish' is not present or not properly configured. 'Wish' is usually present in Linux and SUN operating systems and enables .tcl files to be run as executables.

3.1. You can check the presence of 'wish' on your machine by typing, at the prompt, the command:

wish

If "wish" starts it means that the problem is caused by something else. Contact us at the ESA Earth Observation Help Desk.

If the message "command not found" appears there are two cases:

3.1.1. "wish" is installed but not linked by the PATH variable.

At the prompt, type the command:

echo $PATH

The response should include the string: /usr/local/bin/wish

If it does not, add the wish path to the variable PATH in the ".profile", ".cshrc" or ".bashrc" file (which ever is appropriate - see BEST installation instructions).

C shell:	setenv PATH /usr/local/bin/wish:$PATH
Otherwise:	PATH=/usr/local/bin/wish:$PATH export PATH

3.1.2. "wish" is not installed.

Download and install the 'wish' software and link it following the solution in 3.1.1.

Linux/SUN Solaris: The dialogue boxes of the Tcl/Tk HMI are too big to fit on the screen

1. The optimum display size for the HMIs is 1024 x 768 pixels.

Adjust your desktop settings accordingly.

2. If you prefer, you can adjust the size of the Tcl/Tk HMI by changing the font sizes.

2.1. Open the file "BEST/cfg/besthmi.tcl" in a text editor

2.2. Locate the 'Global settings' section and adjust the following numerical parameters:

	...

	#====================================================================
	# Global settings
	#====================================================================

	...

	# --- Set fonts name ------------------------------------------------
	set fontName -*-helvetica-Medium-R-Normal--*-120-*-*-*-*-*-*
	set mediumFontName -*-helvetica-Medium-R-Normal--*-140-*-*-*-*-*-*
	set largeFontName -*-helvetica-Medium-R-Normal--*-180-*-*-*-*-*-*
	set hugeFontName -*-helvetica-Medium-R-Normal--*-240-*-*-*-*-*-*
	set boldFontName -*-helvetica-Bold-R-Normal--*-140-*-*-*-*-*-*

	...

The size of the frame of the HMI is designed to adjust automatically to fit the text.

Import/Processing

All platforms: Handling of CEOS data with "non standard" filenames

e.g. best. Error opening file: c:\...\VDF_DAT.005

To perform header analysis of a CEOS format product, the directory is specified, rather than the data files inside.

Products on media distributed by ESA are typically contained within a directory called “SCENE1” and the data files all have the suffix “.001”. As explained in the ‘sleeve notes’ of a CEOS format product, subsequent products on the same media would be contained within directories called “SCENE2” (or “SCENEn”) and have suffixes “.002” (or “.00n”). When BEST begins header analysis, it looks at the directory name to learn what the suffix of the data files within will be; it does this by finding the last digit in the directory name.

Therefore, if the data is copied from the original media onto a hard disk and the name of the directory is changed, BEST will search for data files called “[name].00n” where n is the last digit contained in the new directory name.

To overcome the error, you must either rename the data files within the directory according to the file name sought by BEST (see error message), or rename the directory “SCENE1” (or “SCENEn”).

In particular PGS ERS CEOS data delivered by means of FTP can show this different appearance from those on CD and this can create problems using the BEST sw. Here is a simple procedure to overcome this problem.

This is an example on how the product looks after downloading.

To make the data readable from BEST, all the file extensions must be renamed

from xxx.008 to xxx.001

and must be placed inside a new folder called SCENE1

Furthermore it is better to shorten the name of the main folder. For instance from

ER01_SAR_PRI_1P_19910925T102046 _19910925T102103_ESR_001008.CEOS

to

ER01_SAR_PRI_1P_19910925T102046

All platforms: How to find Sub Swath Gain Parameters for the Enhancement Swath tool?

The Enhancement Swath tool requires the user to manually derive the "gain" and "end column" parameters for each of the 5 sub swaths.

a. Select (arbitrarily) a 'master' sub swath, for which the gain value is zero.

b. Then, using image processing software, find the relative intensity (a ratio) of the other sub swaths by averaging over a homogenous area of the image.

c. Compute the inverse to enter as a gain.

Note that the resulting image will not be radiometrically sound, but gives an aesthetically pleasing appearance.

How to import ERS PGS CEOS data properly

To import ERS PGS CEOS data properly it is always mandatory to select in the HEADER ANALYSIS panel the option PGS as source ID like showed in the following example.

RAW data (level 0)

The use of BEST with RAW (level 0) data is limited to header analyses only. See also information under the section Input data. In order to process ASAR/ERS SAR RAW data, a proper SAR image processing is required. In case you have your own SAR processor you can do it directly, otherwise you have to order level 1 data processed with the nominal ESA processor.

Export

All platforms: Output TIFF/GeoTIFF/BIL files appear white

Pixels whose value becomes invalid (‘not a number’ or NAN) in the output from some BEST processes are set to -1e+30. This can cause problems when results are exported and viewed in some image processing software packages, if linear scaling is applied.

To view exported TIFF or GeoTIFF images correctly in other image processing software, it may be necessary to clip the histogram, set a threshold above the NAN value or reassign NAN pixels to a different value.

NAN pixels typically occur at the margins of the image where there are zeroes in the original data due to changes to the Sampling Window Start Time (as illustrated below).

	|00-----|
	|00-----|
	|0-----0|
	|0-----0|
	|-----00|
	|-----00|

The Backscattering Image Generation tool could not use "0" for invalid pixels since valid "0" values may exist in absorbing areas.

All platforms: How to import BIL files into image processing software

Images exported from BEST as flat binary files (Export to BIL), i.e. "[name].bil", are accompanied by two auxiliary files: "[name].txt" (an ancillary data dump) and "[name].ers".

To import binary data into other image processing software packages, it is usually necessary to know some details of the image:

• The data format is BIL.
• The data type is annotated in the "[name].ers" file ('CellType').
• The image size (rows and columns) is annotated in the "[name].ers" file ('NrOfLines' and 'NrOfCellsPerLine' respectively).
• The number of bands is annotated in the "[name].ers" file ('NrOfBands').
• There are no file header or line headers in the image file.

NB: In Envi it is necessary to set up as Host (Intel) the Byte Order field

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry