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Magellan Image Processing
To view the Magellan images you must have software capable of handling
Planetary Data System (PDS) formatted files. We recommend
ENVI by Research
Systems Inc. but others can be used. If you are a student or
faculty member and the University of Nevada, Reno you can access ENVI on
the web via a
Citrix NFuse server.
To view the complete quadrangle of images together, you must create a
mosaic of images in a program such as ENVI. Instructions for
creating a mosaic in ENVI are located here.
To create an accurate mosaic of the images you will need the header
information from each image in the mosaic. We have created a
simple program for extracting the necessary data from the headers (and
other data as well, see the description of the header
data)
Download
the Magellan Image Processing Software.
Instructions for using the Magellan Image Processing Software
This program is meant to be used with the Full Resolution SAR (Synthetic
Aperture Radar) Map of Venus (FMAP) from the Magellan mission. The
purpose of the program is to read a quadrangle directory of FMAP images
and extract relevant information from the images so that the images can
be mosaicked.
Following are the steps to use the Magellan Image Processing Software:
NOTE: You must have the Magellan images on your computer (or on an
accessable network drive before atempting to use this program.
NOTE: At any time before step 4 you have the options of which data you
would like to process into the file. See the * bellow for more
information.
1. Click on the button "Choose Data Folder", this allows you to choose
the folder with the images that need processing.
2. Select appropriate data directory from the dialog and press OK
A list of images that can be processed will appear in the box on the
left
hand side of the program.
3. Select the images to process from the list of available images. You
can select them one at a time by using the arrow button (->), or all
at once by clicking on "Add All Images" (It is also possible to
remove images from the Images to Process box, either by using the
arrow (<-) or by clicking "Remove All Images"
4. Once you have selected all the images that you would like processed
(All images is recommended) click "Retrieve Header Info" to begin
processing
5. Once the processing is complete ("Write to xxxxxx.csv is complete"
appears) you can either process another directory or exit the program.
The data has been placed in the program directory in a comma delimited
file that can easily be read into Microsoft Excel and printed. We
suggest that you open this in Excel or another program and print it for
later reference.
Instructions for Mosaicking images in ENVI
Once you have completed the previous steps for one or more image sets,
close the program. The following steps will guide you through creating a
mosaic in ENVI using the images and data from the Magellan Software.
1. Open ENVI
2. Select File->Open Image File
3. Navigate to the directory where the a set of images are stored.
4. Select all the images you would like to mosaic and click open.
This will then bring up and available bands list with the images you
just opened.
5. Select Map->Mosaicking->Pixel Based from the main ENVI menu.
This will bring up a Pixel Based Mosaic window.
6. From the menu on the Pixel Based Mosaic window select
Import->Import Files.
7. Select the images from the Select Input File box and click OK.
NOTE: this might take several seconds to several minutes to import.
8. When prompted for a mosaic size, enter a value in each direction that
will show all files
NOTE: if you are doing an entire quad, 18000 x 18000 is a good fit.
The imported images will be in the upper right hand corner of the mosaic
stacked on top of each other.
9. Right click on the top image and select edit entry. Find the
entry that corresponds to the entry you are editing in ENVI
(the name is in the title bar).
10. Find the Long Offset(QL), this value should be entered in the
Xoffset box in ENVI
11. Find the Lat Offset(Quad) this value should be entered in the
Yoffset box in ENVI.
12. Click OK in ENVI and the image will be placed in the apropriate
position in the mosaic
Repeat steps 9 - 12 until all images are positioned. In many cases
the rows will not align on the left and right sides, this is normal due
to the positioning of the instruments and the shape of the planet.
Data found in header files
*At any time before retrieving the header information you can select
which data you would like to be retrieved. Select Settings from the main
menu and then Printed Items. The will display a dialog with check boxes
next to the items selected to print. The default is to print all 10
items
(see description below).
Quad ID - The quadrangle identifier of the image
Image Name - The name of the image (this will be of the form flyyNxxx
where
yy is the center longitude of the image N is the hemisphere of
the image north or south and xxx is the latitude of the center
of the image
Maximum Latitude - The maximum latitude value of the image in degrees
Minimum Latitude - The minimum latitude value of the image in degrees
Eastern Longitude - The easternmost longitude value of the image in
degrees
Western Longitude - The westernmost longitude value of the image in
degrees
Latitude Offset (Planet) - A decimal value representing how far from the
center of the planet the bottom of the image is
(negative numbers go up or North)
Long Offset (Quad Center) - A decimal value representing the distance
from
the center of the quadrangle the left edge of
the image is
The following two values are calculated by the program to work with
Research
Systems Inc.'s ENVI visualization program and it's mosaicking component.
Long Offset (Quad Left) - A decimal value representing the distance from
the left edge of the quad and the left edge of
the image
Lat Offset (Quad Top) - A decimal value representing the distance from
the
top of the quad and the top edge of the image
The minimum needed for mosaicing in ENVI is the image name, Long Offset
(Quad Left) and Lat Offset (Quad Top)
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