Each map element (Operators, Filters, etc.) has a specific function, described below.
At the end of this guide are some useful hints and suggestions.
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Clicking this icon pops up a highly condensed guide to finding THEMIS
images, aimed at first-time users.
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Operator buttons control what a mouse click on the map does.
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After you click the Zoom In operator button, a mouse click on the map recenters the map on that point and zooms in by a factor of about 2. You can zoom in repeatedly. Distortion will occur in some areas, because the map is a simple cylindrical projection.
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After you click the Zoom Out operator button, a mouse click on the map recenters the map on the point and zooms out by a factor of 2. You can repeat this until the whole map is visible.
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After you click the Pan operator button, a mouse click on the map recenters the map on that point without changing the magnification.
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After you click the Select operator button, a mouse click anywhere on the map looks for a THEMIS image covering that point. If any exist, a link for each
image appears in both the Thumbnail frame and the Image List. Click either the
thumbnail or the reference number to open a new browser window with details of that image and downloading options.
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Clicking the Link to this Page operator button creates a link in your browser's address window that captures the current filters,
map background, zoom-in state and chosen images. If you save the link as a Bookmark or a Favorite, you can return to that point at any time.
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Clicking the Help operator button opens this user guide.
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The position display gives the martian latitude and longitude of the
mouse point in degrees and decimals of a degree. Latitude is given first and runs from 90° north to 90° south. Longitude increases eastward from 0° to 360°, measuring from the central meridian.
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Release
The THEMIS project began releasing data to the public every three months beginning in October 2002. All releases are grouped together by the mission year* in which the data were collected. A year on Mars lasts roughly 687 days. The latest release, dated in the form of month/year, is also presented separately. (When the map loads, a release has been chosen.) Selecting a different release updates the map, showing the images from only that release.
* This year count started when the spacecraft (Mars Odyssey, or MO) arrived. For the purpose of long-term observations, however, scientists also have a chronological Mars year count, which began April 11, 1955. In this chronological system, MO year 1 for THEMIS occurs at the end of Mars year 25. |
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Choosing all releases redraws the map to show the footprints of all images that meet the chosen Time of Day and Camera filters (see below).
Choosing daily images retrieves the footprints of all Images of the Day that meet the chosen Time of Day and Camera filters. Choosing no releases clears the map. |
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Time of Day
Choosing a Time of Day filter refreshes the map and shows the footprints
of images selected by that filter.
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Choosing daytime
shows only images taken in daytime. Footprints of daytime images (visible or infrared) tilt toward the right. Daytime is the default choice when the map loads.
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Choosing nighttime shows only nighttime images. Footprints of nighttime images tilt toward the left.
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Choosing day + night shows both.
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Choosing none clears the map.
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Choosing a Camera filter refreshes the map and shows the footprints of images selected by that filter.
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Choosing visible
shows the footprints of visible wavelength THEMIS images. Visible image footprints are depicted in blue.
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Choosing infrared
displays the footprints of infrared THEMIS images.
Infrared images have footprints in red.
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Choosing vis + ir
displays both. This is the default choice when the map loads.
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Choosing none
clears the map.
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All Background maps are simple cylindrical projections and have a resolution of roughly 64 pixels per degree, or about 1 kilometer (half a mile) per pixel. The projection becomes increasingly distorted toward the poles.
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Choosing
albedo
displays a grayscale surface map derived from Viking Orbiter data. At right is an albedo thumbnail of the Valles Marineris region.
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Choosing
shaded relief
displays a grayscale shaded-relief map created
from Mars Orbiter Laser Altimeter (MOLA) topographic data. At right is a
shaded-relief thumbnail of the Valles Marineris region.
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Choosing
mola
displays a vividly colored shaded-relief map derived from
Mars Orbiter Laser Altimeter (MOLA) topographic data and United States
Geological Survey (USGS) digital maps. At right is a mola thumbnail
of the Valles Marineris region. The mola background is the default
choice when the map loads.
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Choosing
mola 2
displays a traditionally colored shaded-relief map
derived from Mars Orbiter Laser Altimeter (MOLA) topographic data and
United States Geological Survey (USGS) digital maps. At right is a
mola 2 thumbnail of the Valles Marineris region.
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What you see on the map reflects your current choices of filters and background.
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In this example, the user chose daytime infrared, nighttime
infrared, and visible wavelength images on a grayscale shaded-relief background.
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In this example, the user chose daytime infrared images and the mola 2 color shaded-relief map.
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The Image List gives the reference numbers of any THEMIS image footprints that cover the map spot the mouse clicked on (in Select Mode).
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In the example at left, four infrared (I) and two visible (V) wavelength
images were found. Clicking the I02152002 link would pop open a
window providing detailed information about the image and choices of image
formats for downloading.
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When you choose the Select operator (see above) and click on the map,
the Thumbnails frame shows small versions of any THEMIS images
covering the spot the mouse clicked on.
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In this example, one infrared and one visible wavelength image
were found. Clicking any thumbnail pops open a window giving detailed
information about the image and choices of image formats for downloading.
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