Planet Four Talk

Scaling Factors

  • pete-j by pete-j

    As far as I am aware, each of the images is 840 x 648 pixels; for example, some of the HIRISE image state that the resolution is from 24.7 cm/pixel (with 1 x 1 binning) to 49.3 cm/pixel(with 2 x 2 binning).

    My question is, which of these resolutions may be used to work out the scale? I know that I have raised this before (this was when one parameter for the resolution existed). The confusion arises that we could potentially have two sizes for this image. They can’t both be right? I conclude that one must be correct or my interpretation is incorrect?

    1 x 1 binning:
    840 x 0.247m = 207.48m, 648 x 0.247m = 160.06m. Hence image size is approx. 207m x 160m.

    2 x 2 binning:
    840 x 0.493m = 414.12m, 648 x 0.493m = 319.64m. Hence image size is approx. 414m x 320m.

    I earlier posted comments (a few weeks ago) alongside a few of the images as I felt that it was useful to have a sense of scale of what we were seeing in the images.

    Posted

  • mschwamb by mschwamb scientist, translator in response to pete-j's comment.

    Hi,

    It depends on the cutout and its parent HiRISE image. Some where taken in binned 2x2 mode, others not. The HiRISE link below the cutout on Talk will take you to the HiRISE page where it will tell you the binning and the pixel scale cm/pixel.

    If you can point the APF id of an image you're confused about, we can go through the pixel scale calculation .

    Cheers,

    ~Meg

    Posted

  • Kitharode by Kitharode moderator

    Hmm ... Sadly that seems to make a nonsense of my recent 'Method for Measuring' post, eh? Other than throwing rubbish into one, I don't know anything about binning. Ho hum, back to the drawing board. 😦

    But I'll check out the HiRise page and see if I can make some sense of the scale. It'd be really good to get a handle on this measuring lark, for all sorts of mini-projects.

    Posted

  • pete-j by pete-j

    Thanks for your replies! Actually I found the image to which I was referring to and it was APF00026aw. I did in fact access the HiRISE page, it is where the parameters where from.

    The confusion arises in that there are two scaling possibilities as I understand this? Like Kitharode, I do not come across ‘binning’ in everyday life as I do not process images (apart from encountering them here). Even though my background is in astrophysics.

    Any clarification would be appreciated.

    Cheers,

    Pete.

    ps perhaps on a future paper, the size & distribution of fans on the Martian surface could be a useful topic for investigation?

    Posted

  • mschwamb by mschwamb scientist, translator in response to pete-j's comment.

    So in this case it looks like that image had different parts of the observation taken in different binned modes (2x2 and 1x1) so that's why they listed both. The camera has a few different CCDs so in this case some of them were commanded to be in 2x2 mode and others were in 1x1. I'm sure there's a way to disentangle of the color observation (the portion of the observation we used on HiRISE is in 1x1 or 2x2. The image headers (called labels) are located on the HiRISE page under 'ADDITIONAL IMAGE INFORMATION'. So with some luck there is the information you're looking for and this document might help explain everything in the label.

    You can see for this observation, it only lists one binning. So for most HiRISE images you're usually okay to just use the single number it quotes under original image-scale.

    ps perhaps on a future paper, the size & distribution of fans on the Martian surface could be a useful topic for investigation?

    Different regions do have different sizes. Ithaca tends to have much larger fans thought because the region is flatest.That's already known from the analysis previously done before Planet Four, but we can do this analysis in much better detail. Likely our first or second paper will present typical average sizes of fans in the different targeted regions. We're aiming towards submitting the first paper from the project in February of next year (fingers crossed).

    Cheers,

    ~Meg

    Posted

  • pete-j by pete-j

    Thanks for the explanation Meg and the additional reference source, which I appreciate. Most of the images I have encountered and looked at (i.e. the HiRISE data) show just the one binning mode. It seems to be a minority (in my sample at least) that have the dual observations.

    The very best wishes with the paper!

    Cheers,

    Pete

    Posted