euv_imtool - IMAGE EUV Image Processing Tool
Version 1.39 - June 21, 2005
euv_imtool displays and operates upon EUV skymap images. Once an image
has been displayed, features such as the plasmapause may be mapped in
L-shell vs. magnetic local time or magnetic longitude. Plots of the
radial and azimuthal brightness profiles may also be generated. Data
from both the feature mapping and brightness plots may be saved for
The program can either read the IMAGE EUV and orbit UDF files directly
or read a FITS format EUV image produced by euv_imtool itself (see Output options below). Additionally, FITS files
produced by the on-line FITS data request form (http://euv.lpl.arizona.edu/euv/data)
may be used as well. Note that beginning with version 1.26, euv_imtool
uses revised values for the pixel overlap between cameras and
camera-specific plate scales when performing line of sight calculations.
If FITS images created before this revision are loaded, the program will
issue a one-time warning. For best results, obtain new versions of the
FITS data files for the time period of interest.
The FITS file data input method requires the IDLASTRO package,
available from http://idlastro.gsfc.nasa.gov,
and EUV skymap FITS format images produced by program euv_imtool.
The UDF data input method requires the following:
The UDFToIDL package is now the default for euv_imtool. If you want to
use the LANL udf-dlm developed by Ed Santiago, simple add '/udfdlm' to
the command line when starting euv_imtool.
- the UDF software
- The UDFToIDL package from Chris Gurgiolo or the udfdlm package
- EUV and OA (orbit) data for the time period of interest
There are two output formats:
- JPEG - save the displayed image as a JPEG image
- FITS - save the data array as a FITS file (includes background
For each output format, there are two menu items in the File
menu. The first in each pair saves the information from the image
display in the main window, the second saves the contents of the full
frame display window (see below for more information on this window).
Line of sight calculations
In order to perform the line of sight calculations, the Earth center
position must be interactively set for each image. Automatic centering
is difficult due to spin phase jitter and changes in the spacecraft spin
vector over time (however, see the section entitled Auto
Centering below). To set the center, click the Define Center
button, position the mouse cursor at the center of the Earth and click
once to set the center. A dashed circle is drawn to aid in centering,
and is then left to mark the outline of the Earth for the chosen center.
Once a center is defined, it may be retained when a new image is
loaded by clicking the Keep Center? button.
After defining the center, a single mouse click in the display
window generates the following line of sight parameters:
Points may be deleted from the set by clicking the right mouse button
in the vicinity of the point.
- minimum L shell value along the line of sight
- for the point at which minimum L occurs:
- magnetic local time (decimal hours)
- magnetic longitude in the MAG coordinate system
- 3x3 pixel average data value
The line of sight calculated quantities may be recorded in an output
file for a series of mouse clicks by specifying a file name in the Output
file: text box and clicking the Record File button. Each line
in the file contains the following items:
(All quantities refer to the point at which minimum L shell value
- magnetic longitude (degrees, MAG coordinate system)
- magnetic local time (hours, SM coordinate system)
- minimum L shell value along the line of sight
- X coordinate (SM system, earth radii)
- Y coordinate (SM system, earth radii)
- Z coordinate (SM system, earth radii)
- 3x3 pixel average data value
- frame midpoint time stamp
If the Sort by MLT check box is checked, the output file is
sorted in increasing magnetic local time, allowing the points to be
defined in any order. If not checked, the points are written to the
output file in the order in which they were entered. The center may be
re-defined at any time before writing the output file, since all
quantities are re-calculated as the output file is written.
If the Append check box is checked, the points are appended to
the recording file. This allows recording measurements from a number of
frames into a single output file.
If the continuous check box is checked, the minimum L,
magnetic local time, magnetic longitude and pixel average will be
displayed continuously as the mouse cursor moves over the image.
To enable auto-centering, click the auto center check box. The bias
drop list adds a bias along the Sun line in the Sun direction. Units of
this bias are 0.3 degree pixels corresponding to the pixel size in the
main image display window. The center is determined when the data is
loaded by correlating an artificial image of the bright ring around the
Earth with the EUV image. Note that this is an experimental feature
that is still under development.
Image processing operations
The background may be subtracted from the currnet image using the
Subtract Background menu item.
Parameters are entered using an interactive dialog.
There are two methods of background removal, depending on the state of
the de-banding subtraction check box. If unchecked, the
background level is determined by averaging the counts over the
rectangular portion of the image specified in the minimum and maximum X
and Y input fields (Note that these are 0-based indices). This constant
value is subtracted from the entire image. If the de-banding option is
chosen, the minimum and maximum X values are ignored, and a background
level is determined for each column in the image by averaging over the
area specified by the minimum and maximum Y. This type of background
subtraction may be used to remove the vertical banding sometimes seen
during high noise periods.
The background subtraction may be undone by using the Revert Image
The Dump GSM menu item enables dumping the image to a text file
containing the following items for each pixel in the original (140x150) pixel
Points less than 1.05 Earth raddi from the center of the image are
omitted in this dump.
- GSM X coordinate of the minimum L shell point (in Earth radii)
- GSM Y coordinate of the minimum L shell point (in Earth radii)
- GSM Z coordinate of the minimum L shell point (in Earth radii)
- the minimum L shell value
- the pixel brightness in counts
- pixel index in the horizontal direction
- pixel index in the vertical direction
Additional Image Display Windows
Zoomed Image Display Window
The Show Zoomed Display button shows a separate window
containing a larger (1.5x) version of the displayed EUV image. All
operations (background subtraction, data values readouts and line of
sight calculations) work the same way in the zoomed window as in the
display in the main window. Note that the image center may be defined on
either display; an appropriate center for the other display will be used
by the program. The button at the bottom of the window toggles the
displayed image size between 84x90 and 84x180 degrees. The larger
size may be necessary for plasmasphere feature viewing and measurements
when the spacecraft is close to the Earth.
Full Frame Image Display Window
The Show Full Frame Display button displays a separate window
showing the full (360 by 84 degree) EUV camera frame. Readouts at the
bottom of the frame show the data value at the cursor position and the
right ascension and declination at the cursor (once the Earth center has
been defined). The full frame image will appear only if the data source is
UDF or a full-frame FITS image file.
Contour Map Overlays
The Overlay/Remove Contour Map button enables and disables
plotting of contour maps on the image display. Currently, 8 levels are
drawn, but in the future, more flexibility may be added, allowing the
user more control of the contour levels.
Solar Wind Plot Window
The Show/Hide Solar Wind Plot button enables and disable
plotting of selected solar wind, IMF and geomagnetic indices in a
separate window, centered around the midpoint time of the EUV frame. The
required data files (solarwind.dat, kp.dat and dst.dat) must be either
in the current directory or in a directory pointed to by an environment
variable named SWDATA. If these data files are not found, this button
will remain disabled. These files may be obtained via anonymous ftp to
euv.lpl.arizona.edu, in the directory /pub/image/data/solarwind.
There are a few controls at the bottom of the plot window. The
slider adjusts the width (in time) of the plot. The Fixed/Auto
button next to the slider toggles between pre-selected plot minima and
maxima and auto-scaled plot limits, and the PNG button writes a
PNG image file from the solar wind plot window.
2D radial and aziumuthal plots
After the center has been defined in either of the two image display
windows, a single mouse click will produce two-dimensional plots in a
separate window: an azimuthal plot of brightness vs.magnetic local time
and a radial plot of brightness vs. L-shell. This feature may be turned
off and on by the Enable (Disable) Radial/Azimuthal Plots button
in the main window. Once plotted, the data may be dumped to a text file.
Supply a base filename in the text widget at the bottom of the plot
window, then press the dump data button. An output file will be
generated for each of the two plots, named by appending 'azi' and 'rad'
to the supplied base file name. These plots may be produced by clicking
in either the main window or the zoom window, but is only supported in
the non-expanded zoom window.
Batch FITS and IDL save file production
Batch mode operations enable the mass production of FITS format output
files and IDL save files from the UDF data over a range in time. The Set
start time... and Set stop time... menu items allow the user
to set the start/stop time for the period of interest. The time of the
current frame is loaded by default, but any time may be specified. Then
selecting the Make FITS file menu item will cause euv_imtool to
generate FITS output files for all frames in the specified time period.
The Make FITS file (Full Frame) item does the same thing, except
that it writes the full 84x360 degree EUV frame into the output FITS file.
IDL save files may be created in a similar fashion, using the Make
IDL save file and Make IDL save file (full frame) menu items.
The first saves the 140x150 image array corresponding to what is
displayed in the image display window. The second saves the full
frame (140x600 pixels). Within the save file, array names are
based on the image midpoint time year, day of year, hour and minute in
the form Eyyyydddhhmm (e.g. E20001450650). The save file itself is named
after the first array it contains (e.g. e20001450650.sav).
Use of the '/batchsub' command line parameter causes the background
to be subtracted before writing the FITS image or IDL array, using the
current background subtraction parameters.
The Save Settings menu item in the File menu saves some program
settings (e.g. the UDF start time and background subtraction settings)
that may be re-loaded the next time the program is run. For Mac and
Windows platforms, the settings file is called 'euv_imtool.ini' and will
be written to the current directory. If this file is found, it will be
loaded automatically when euv_imtool starts. On Unix and Linux
platforms, the settings file is named '.euv_imtool'. When euv_imtool
starts, it first checks the current directory, then looks in $HOME. When
the settings are saved, they are written to the current directory only
if they were loaded from that directory, otherwise they are saved to
Compiling and running euv_imtool
The compile_euv_imtool procedure is provided to make sure that all
necessary euv_imtool routines are located. It may be run like:
For convenience, the compiled routines may be saved and restored in
a later IDL session:
IDL> save, /routines, filename='euvimtool138.sav'
Also, note that euv_imtool uses some routines from the IDL examples
directory tree, so the examples programs must be installed and included
in the IDL search path.
Dennis Gallagher provided the original IDL routines that calculate the
line of sight and minimum L-shell along that line. Bob King developed an
analytic solution for finding the minimum L along the line of sight.
This was ported to IDL by Tim Bavaro for inclusion in euv_imtool. Tim
Bavaro also contributed the solar wind plot window introduced in version
1.25. Bill Sandel contributed a modified line of sight routine and
Leonard Garcia at Goddard Space Flight Center added the contour map
overlay capability. The color map selection code was originally written
by Martin Wuest at Southwest Research Institute.