From previous ObsParis / CDS meeting

More use cases from Pierre Fernique 26/6/2017, based on Aladin 10 prototype (v9.630)

Detailed Use-case - Manual image registration

  • 1- Simultaneous visualisation in Aladin of Mars surface HiPS (from THEMIS data) and a HR context image of the Curiosity landing site  (from Wikipedia)
    Load URL (in Location field)
    Open branch "/local/Planet" and pick up the Mars THEMIS HiPS
    Click on multiview (below the main window) and drag & drop the landing site image on Aladin window.

  • 2- Registration of HR image by manual match of control points (x,y) -> (long,lat) (based on crater centers).
    Use Aladin function: Image -> Astrometric calibration -> tab "by matching stars"
    The image is located in Gale crater at lat = -4.6° (S) and long = 137.4° (E) = 9.16h (not where indicated in Fig. 1 above).
    Once you've found the area, you may want to rotate the HiPS to match the JPEG image orientation (Ctrl+clic/drag) to make it simpler. The current version of Aladin requires to perform this operation with no inversion of HiPS longitudes (ie, longitudes untouched in Properties panel, so that the THEMIS map is inverted; to be corrected). Click on "Create" button when done.
    Well, the procedure is really tricky and seems unstable as can be seen in Fig 3a - comments welcome on this. Plus, the image is simply oriented and scaled, no internal deformation is applied.

  • 3- The newly registered image can now be superimposed on the HiPS, just go back to single view and selected the Mars map; opacity of the registered image can be adjusted with the cursor in the image icon - see Fig 3 & 3a (3a is the registration of a higher resolution image, also from Wikipedia, on the first registered image)
    Fig 3

    Fig 3a

Update, 7/2/2018, v10.075

Based on more recent Mars HiPS, the jpg image below (Fig 3d) is projected based on 3 control points: the small crater in the upper left corner and 2 elt on the slope along the rover path. The jpg image includes the projection info and can be superimposed on a Martian HiPS (Fig 3b: load Mars / Themis dayside HiPS, load image, and tweak opacities). Profiles drawn on an image can be translated to other images when everything is registered (Fig 3c - beware this is a dummy case for the sake of illustration only).

Fig 3b

Fig 3c

Fig 3d: "Astrometrically calibrated" (ie, projected) jpg image to plot in Aladin

Detailed Use-case - panoramic HiPS

  1. Retrieve a panoramic image from Curiosity MASTCAM camera (24 April 2016) from the JPL public outreach site. We use the Jpeg image with highest resolution (29163x6702 in size, ~ 100 MB).

  2. We will manually generate an astrometric calibration (registration, really) in Cartesian coordinates for this image (pixel size = 360./29163., reference point 0,0 long,lat at image center).

    Don't even try to load the image in Aladin, this may be very long.

    Create an ascii file with same name root as the panoramic image and extension ".hhh" (ie, PIA20332.hhh), keep it in the same directory as the image.

    Fill it with the information below:

    NAXIS1  = 29163
    NAXIS2  = 6702
    CRPIX1  = 14581.0
    CRPIX2  = 3351.0
    CRVAL1  = 0.0
    CRVAL2  = 0.0
    CTYPE1  = RA---CAR
    CTYPE2  = DEC--CAR
    CD1_1   = -0.012344832316027706
    CD1_2   = -0.0
    CD2_1   = -0.0
    CD2_2   = 0.012344832316027706
  3. Generate the HiPS in batch mode using the following command from Aladin's directory:

    java -Xmx4g -jar Aladin.jar -hipsgen in="DirectoryOfOriginalImage" out="HiPSTargetDirectory" color=jpg id="LESIA/SE/Mars/color"

    The result will be stored under the current directory in HiPSTargetDirectory.
    If you want to try other options, they have to be inserted with no space surrounding the "=" character. List available here:
    particular, "partitioning" may be a time saver, depending on available memory; partitioning=4096 may do with a standard laptop).

  4. Computing time is ~ 20-40 min on a small machine (a 2012 i5 laptop). The result is about 1.3 times larger than the original image.

  5. Load the resulting HiPS in Aladin (just drop the HiPS folder on Aladin window). Using a MOLDWEIDE projection may help navigating in the image — cf Fig 4 and following, at various enlargements. Moving around the panorama is quick and smooth, and really informative. In particular, stratification at various scales can be visualized at different distances (eg, in close rocks at 10°/26°, or in the distant hills at 34°/163°), and various reliefs can be explored (eg, white hills at 33°, smaller ones at 33°/165°, close sand pond at 14°/140°).
    Fitting the color scale dynamics (right click/drag) improves local contrast. Indications of orientation are currently meaningless (they may be inhibited in the future, or better, replaced by azimuth/elevation angles if available).
    A precomputed test HiPS is available at (Mars Stimson panorama).

  6. In the output HiPS directory you also get a web page. Launching it will display the HiPS in Aladin Lite in your browser. Click on the top-right arrows to enlarge the view and navigate the panorama (Fig. 7)

Fig 4

Fig 5

Fig 6

Fig 7

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