Planet Four Talk

A question of scale.........

  • AUricle by AUricle

    I know all these images are supposed to have a resolution of 0.5 - 1.0 m per pixel, but looking at these two images, and a slew of others, it is difficult to believe those parameters. One looks as if it were taken from orbit, and the other from an airplane. This is an optical illusion?
    enter image description here
    enter image description here

    and again, BOTH images have color 'glitches'.....top has a blue and red glitch, bottom has red glitch near the right edge, and an upside down flagstick planted by an irate golfer, no doubt.................both images are rotated 180 deg.

    Posted

  • JellyMonster by JellyMonster

    Yes, I see what you mean. The top image seems to be of a higher resolution than the lower one. Although I would say that the bottom picture also looks a little blurred. I don't think much of the putting green though 😃.

    Posted

  • wassock by wassock moderator in response to AUricle's comment.

    Do you have the original image ref's? - I'm trying to get a handle on figuring where the pics come from - going back to the original HiRise would give us the scale.

    Posted

  • AUricle by AUricle

    enter image description here

    50e73d6d5e2ed212400012cc.jpg for the upper

    50e741375e2ed212400032a9.jpg for the lower

    If you mean the "APFxxxxx used here, I can't find it. It's in a collection, but if I try to "load more" too many times, the window freezes up and goes black, so I can't get deep enough into my collections to find these

    Posted

  • AUricle by AUricle in response to JellyMonster's comment.


    Sorry Dave. I mis-spoke somewhat. Though resolution may be part of it, what is most obvious (if not an illusion) is an apparent distance perception between the camera 'eye' and the ground. So it seems to be a magnification thing instead of a resolution problem. Simply, are these images magnified? Some more than others? Or not at all?

    Posted

  • JellyMonster by JellyMonster in response to AUricle's comment.

    Ah yes, that might explain the blurry bottom image. A similar situation occurs when using Google Maps. If you zoom in too far, the map gets a little fuzzy... zoom out again and everything becomes clearer and more detailed. We should ask a scientist on this one.

    PS those animations are clever (and funny) - but they get a bit annoying after a while and it puts me off typing 😃.

    Posted

  • AUricle by AUricle

    but they get a bit annoying after a while and put me off typing 😃

    Just trying to respect your authority. 😉 OK, I'll stop, Your HighJellyness

    If you zoom in too far, the map gets a little fuzzy

    Exactly, Dave. Like focusing a telescope. If you have more magnifying power than the resolution of the optics can deliver, you pass a point of optimum "zoom" and everything after that is just blurring the image worse, the 'higher' you zoom.

    We have cameras cirlcing the Earth that read automobile license plates, so why is "dining room table" size resolution settled for at Mars?.......but none of this answers the question of whether or not these images are magnified......either at the camera, or in the processing that is done before we get to see the images . Does anyone know the answer???

    Posted

  • JellyMonster by JellyMonster

    AUticle, I will get a scientist on it right away... (wonders whether to report AUricle for sarcasm)

    Posted

  • AUricle by AUricle

    "AUticle, I will get a scientist on it right away"...

    LOL!!!......Good one Dave!.......(*Auricle notes JM beginning to throw his weight around, obviously relishing his new power)

    (wonders whether to report AUricle for sarcasm).........Who, Me??

    AUricle nods sadly, remembering, "Power corrupts. Absolute power corrupts absolutely..........and worries "He's already gone over to the dark side! Auricle wonders *How long can it be before there is a struggle for absolute authority among Los Tres Amigos?

    Finally, to break the dark moment, AUricle thinks,......(perhaps we could have a contest for the naming rights of our new forum sheriffs! Then, Where is Paul Johnson? I could use a good man for this!* Well let's see....."Los Tres Amigo's" is already on the table,.....hmmm, maybe "The Three Muskateers?" Nope, too noble....this is supposed to be FUN......how about "The Three Stooges?"
    AUricle laughs, thinking (Ooooh, that's even better. We can dedide which is Moe, Larry, and Curly (nyuk,nyuk,nyuk!) too! Finally, there is "Three Blind Mice....a bit more genteel for the thin-skinned he mused....

    Posted

  • JellyMonster by JellyMonster

    What about Huey, Duey and Luey? (must change the subject)

    The scientist is having a lie down at the moment but will be here shortly to answer your question.

    Posted

  • AUricle by AUricle

    Haha. That was a good one JM!...Unfortunately............

    Contest rules state; Forum Potentates, other Potentates, or family members, shall be inelegible to win prizes or submit entries. However, any erroneously submitted entries by such hierarchy, may be purloined by forum peons for their own use. "As it is written, so shall it be done....etcetera, etcetera, etcetera.......

    Now if a scientist really shows up, I will be trembling in fear! 😉

    Posted

  • Kitharode by Kitharode moderator

    Don't mess with 'The Mods'! (Shut up Kith - you're a hippy and too old to change).

    AUricle. Thanks for picking up on JM's 'nudge' about the animations. They are fun, but they are distracting. By the way, how did you find out that I was a blind, sword-wielding comedian, born of a Mexican nobleman? You a web-bot?

    JM. AUricle is right; power can corrupt. We need to take care. (Have you seen the button marked 'Ban User'? You could always say your mouse slipped. I'd back you up - All for one and one for the road...) 😉

    Posted

  • JellyMonster by JellyMonster

    AUricle has got away with it this time (I clicked on fan instead of ban 😮).

    The scientist will be here soon (once she has finished her yoghurt).

    Posted

  • AUricle by AUricle in response to Kitharode's comment.

    "They are fun, but they are distracting."

    "The light falls harshly only on the guilty" (Contemporary famous quote from AUricle-- copyright pending)

    "Nudge"? ....Yes....all the subtlety of a full swing with a battle axe. 😉

    "I was a blind, sword-wielding comedian, born of a Mexican nobleman"

    AUricle hesitates ...(hmmm....should I tell him his fellow 'grand-poobah' called him a cartoon Duck?) (That should get the in-fighting started)....

    (Have you seen the button marked 'Ban User'? You could always say your mouse slipped. I'd back you up - All for one and one for the road...)

    AUricles eyes narrow to slits, whispering "I KNEW it" to himself, and recalling lyrics from a Radiohead song......."..when I am King you will be first against the wall...."

    NEWS FLASH!!! In less important elections, a NEW POPE has been selected......end of message

    Posted

  • AUricle by AUricle in response to JellyMonster's comment.

    ("The scientist will be here soon (once she has finished her yoghurt").

    "It's a trick", thinks AUricle. "They want me to hold my breath"
    OK, JM. Whatever you say..............zzzzzzzzzz.........

    Posted

  • Kitharode by Kitharode moderator

    So what was the question again and why do you need a scientist? When they join in they usually talk sense. What good is that on a thread like this? Thin end of the wedge and all that....

    Imagine one of them joining the 'Two spiders walking down the road' thread. "Dear Kith, you seem to have misunderstood what we mean by 'spiders'. They do not 'cross roads', as you suggest in your argument, for two reasons......". Actually, on the right page that could be rather funny. 😉

    Posted

  • AUricle by AUricle in response to Kitharode's comment.

    The question deals with the difference in the way images appear. Some look 'close-up' and some far more distant. I think JM was able to clarify the camera/image "resolution aspect", but no mention has ever been made as to whether some of the images we get have been magnified either by the telescope/camera onboard the MRO, or at JPL when the images are processed. Or perhaps it's just an illusion produced by the size of the imaged surface features....like BIG spiders would appear closer than a field of tiny spiders, etc... (sorry, I meant araneiforms)

    Actually there is another thing I'd like to know. Some observed images look like they were taken when the MRO was directly overhead of the image location, and some look like they're "downrange" at varying angles. Again, just an llusion? Or done to take advantage of lighting to get the most contrast or illumination on an image site?

    Posted

  • mschwamb by mschwamb scientist, translator

    Hi Folks,

    Can we all settle down? I'm reading a draft of a telescope observing proposal that's due in a day or two so I don't have much time to comment.

    I don't necessarily know the full answer, but I can give you my best guess.

    Some of this is orbit I'm sure and HiRES is imaging at the pole so this may a effect from the fact that lat and lon lines are converging (so this effect may be bigger in the images we're showing on the site) since the images aren't map projected so different parts of the images will have slightly different resolutions. For example see the difference on a map projected and unmap projected image here

    Also we're quoting the average resolution, there are more images that may have a different resolution, but I don't know very much about the conditions and specifications the images were taken under. Anya and Michael may have more to say on that.

    Also one thing about resolution - maybe spy satellites have that license plate resolution but not even weather satellites I know of have that resolution. Partly limits on tech in planetary missions is cost, radiation hardened (your iphone is more sophisticated than the computer onboard Mars Curiosity). HiRISE is the most advanced resolution camera to be sent to Mars at its time.

    Hope this helps,
    ~Meg

    Posted

  • Kitharode by Kitharode moderator

    Thanks Meg. Point taken, and good luck with the proposal. I'm sure the guys will agree that we've got plenty to play with now and hopefully we'll get along in our investigations without you (for a bit).
    What do you say guys? 😉

    Posted

  • mschwamb by mschwamb scientist, translator in response to Kitharode's comment.

    BTW, I am kidding.
    ~Meg

    Posted

  • AUricle by AUricle in response to mschwamb's comment.

    OH, beeehave!!
    Gigantic ROFLMAO Meg! THAT was priceless! 😉

    You'd make one HELL of a fisherman!( or maybe you already are? (sorry, fisherwoman just sounds weird 😉 .....you masterfully cast the bait,.....got your bite,......and then, with the barest flick of the tongue... (" BTW, I'm kidding") set the hook like a pro!

    Thanks for stopping by for a 'bite'....guffawww

    Posted

  • Kitharode by Kitharode moderator

    I've made a guess that BTW = By The Way. ROFLMAO is waaay over my head. Is it Klingon for Mayonaise? 😃

    Useful answer I thought...

    Posted

  • AUricle by AUricle in response to mschwamb's comment.

    Why Mister Kith, Sir! I never realized you were such a "cough-cough..... "diplomat".....suddenly

    " I'm sure the guys will agree".........."What do you say guys"? OK. You lead, we'll follow, bud.

    Are you feeling OK, ol' boy! Such shameless pandering?? I would never have guessed. ("It's that p-o-w-e-r effect", mused AUricle. "Pity, he's so likeable, and normally such a quick-witted fellow.")

    Please accept my handkerchief, so you can clean up that...umm,... "rustgrust" hued blotch off the tip of your nose!
    ...and...What... on... Earth? Is that a FISHHOOK protruding from your cheek, Guv'ner? 😉

    Posted

  • Kitharode by Kitharode moderator

    It's the ups and downs of my life AUricle. I'm bi-polar (manic-depression). Sometimes I'm a bit 'deep and slow', other times I'm on fire. I'm lucky though, 'cause I don't 'suffer' from this condition, it's often quite wonderful. 😉

    I had you down as one of 'the guys' - you are really, aren't you?

    Posted

  • AUricle by AUricle

    Kith,

    I trust you are not 'pulling my leg' here.....

    ...and I applaud your attitude, because I have seen B-P D up close (my youngest child) and I can empathize with evey statement you made.The 'up' times can be quite amazing (music and writing happen to be his 'go-to' things, and when he's up the creativity is almost scary. The other side of it can be scary too. I've often told him, "Pain is inevitable. Suffering, optional. It's a feeble attempt to slay a dragon I can't even see.

    My wife has a skin condition (over 20 years now) that at times is so aggressive and painful, I can't believe she bears it. Yet she's one of the most humorous and most caring people I've ever known. If it were me, I'd have probably committed suicide long ago. So again, kudo's to you.

    Congrats too, on the "Mod Squad" appointment. All of you guys. If I've played the "ax-to-grind" or bad case of "red-ass" thing about your 'titles' too far, shame on me. 'Fun' at the expense of others is never a good thing I sincerely apologize if any of it seemed offensive or demeaning. Rest assured, if you guys weren't a likeable and interesting bunch, I'd be doing therapy to figure out why I spend so much time following and responding to your posts......(but Dang! who'd they bribe for those titles).....Oops, sorry. The 8 year-old demanded one more tantrum 😉

    As far as your last remark/question goes......well I guess I deserved that, but how I answer that is not what will rule the day. As they say, "Talk is cheap".

    Oy! Is this a Mars forum? Can we have a group-hug, sing a chorus of "Kumbaya" and call it a night? I'm beat. 😉

    Posted

  • mschwamb by mschwamb scientist, translator in response to AUricle's comment.

    More like I realized my tone came across as harsh which is not what I originally intended. Apologies to Katharode for not picking up that while writing it.
    ~Meg

    Posted

  • Kitharode by Kitharode moderator

    Hi AUricle. No, I am what I am and I make best use of it. My catchphrase is 'I don't suffer from manic-depression, I enjoy mental-diversity'. I've seen nothing offensive under the circumstances so no worries there, please. You've got the toughest job, because I know what it's like to live with someone like me and hey, we all gotta let off steam sometimes 😉

    Glad to hear your son's into music creation, he'll be good at that for sure. Don't know his age and interests, but at the right time he might want to see what I do with my 'uptime' at http://ancientgreekmusicalnotation.co.uk/

    Re 'the Mods'. Thanks muchly. Got an invitation and just said yes. No idea why I was on the hit list, but I wasn't gonna turn down the 'Help Needed' email from P4. (They'll learn to regret it, nyaa ha ha haaaar)

    So - I remember you repeating the question, and then you got an answer, so what comes next?

    (PS. If you want me to remove any of the above from your thread let me know. I'm ok with it) Cheers.

    Posted

  • AUricle by AUricle in response to mschwamb's comment.

    Your post was actually pretty benign, Meg. What I did with it was not. If anything, I was the one who amped it up and made it sound like 'barb'. Please accept my apology

    Posted

  • JellyMonster by JellyMonster in response to AUricle's comment.

    It's too late AUricle - I have already banned you for uncontrollable behaviour 😃.

    Seriously though, have you ever thought about writing books? It is very good stuff y'know.

    Posted

  • AUricle by AUricle in response to mschwamb's comment.

    Thanks Kith,

    You be the judge. You were the undeserving target, so if you want to remove especially 'the one' feel free to. On the other hand, perhaps public embarrassment would serve a purpose.
    I tend towards excess, and they'll serve as a reminder not to get carried away in the pursuit of a laugh....or anything else!

    I remember you repeating the question, and then you got an answer, so what comes next?

    Wellllllllll-ahhhhh, the answer (for me) was sort of 'menza-menza' (in Italian,..... we mean approximately "50-50", "half 'yes'-half 'no'. I think the question of the perception of looking "down-range" may be caused by the extreme convergences of the long. and lat. curvature around the poles. That is what I got from Megs answer, though even she called it 'her best guess' if I'm not mistaken.

    That leaves the question of magnification of the images, because I get the possible resolution variances caused by terrain or orbital perturbations across non-'mapped' images. That was helpful info. So, if I'm correct, Meg said K. Michael Aye or Anya P. would be better qualified to answer that particular question.

    Posted

  • Kitharode by Kitharode moderator

    (I judge we leave it as is. Reading text is not as good as talking face to face, so misunderstandings and mistakes are more easily made. No harm's been done, we've all learnt something, it may even have brought us closer together.) 😃

    Apertures, focal lengths, magnifications - Arggh. They were never my thing, so I can't help there. I get it, but I don't do photography and I'm only interested in looking through a telescope. Don't fiddle with them (I'm a guitarist) or collomate them (that might even be spelt wrong) or try to work out its resolving power. Sorry.

    I'm confused about Meg's lat and long statement. I'm missing the point entirely. I'd have thought, give or take a small deviation here and there, that if you take a photo of a unit area of the surface of a planet, at a given altitude, that any other unit area of the planet would 'be the same' from the same altitude. Reading Meg's statement gives me an image of the landscape converging along with the lat/long lines - or something. Can't be that, so what's she saying?

    Posted

  • AUricle by AUricle in response to JellyMonster's comment.

    have you ever thought about writing books? It is very good stuff y'know

    Why,...thank you Jman! Just when I was thinking that I'd done nothing but make myself look like a total lout, you've come along and talked me off the window ledge 😉 Oh Happy Day!
    That tells me that somewhere buried in that mud I was slinging, someone spotted my real intent, which was humor. (...but you shouldn't be so quick to unshackle the subdued beast, friend, as he is wily and dangerous still...warns AUricle)

    Actually Dave, yes I have, though I never really tried.....well by that I mean I never looked at it in a 'professional' way. I did do some speech writing years ago for acquaintances Just the thought of staying with a particular idea for a couple-hundred pages makes me go blank. You think I might have a "focusing" problem?...lol

    Hey, btw....Dr Candice Hansen our P4 P.I. has posted up some tidbits on the blog site. Have you had a chance to see it?

    Posted

  • Kitharode by Kitharode moderator in response to AUricle's comment.

    Yes, we got your intent as humour. We were just waiting for it to begin. (ho ho). Makes you go blank, so you're gonna turn into a polished optic then? Focusing problem mirrors my situation precisely.

    I'm off to read the Blog now. Thanks for the reminder.

    Posted

  • AUricle by AUricle

    Kith,

    Here's what I think is being said. Imagine along with me. You'll get this immediately. If you are standing at the equator looking due E. or W., the horizon is going to be x km. away (given 'flat' ground) , but do the same thing at -85 deg. latitude or +85 and your horizon...all else being equal, is going to be much closer. (I'm sure there must be a mathematical formula for this, but I know my limits, so I'll stay far away from that!) Distance, and with it perception of area, is visually compressed.

    Now I can easily enough grasp the concept of what Meg was saying....that an equivalent feature at the equator would look larger near the pole. I think it's somewhat similar to what we experience when watching a rising moon. Near the horizon it looks HUGE, but when it's high in the sky, it's about 1/3 that apparent size.

    OK. Given that we're not comparing equatorial images to polar images, I'm not sure to what degree those differences would be apparent, and not knowing the latitudes of the reference images I posted makes it hard to 'test' the concept. But I imagine the same 'effect' would show from orbit just as it would from the surface. Then again, maybe this is not at all what Meg meant, and I've just blabbered on for nothing 😉

    Posted

  • Kitharode by Kitharode moderator

    I've recently read that yardangs are 'equatorial'. I'd always assumed they were more southerly.

    Second paragraph. Yes, I'm happy with the 'big moon' thing. Something to do with not having anything familiar (house, tree) in same area of sight when moon high up. We can say optical illusion, however it works.

    First paragraph. I'm reading 'flat ground' as 'smooth-ish surface of a sphere'. That ok? I'm on the equator looking E/W, horizon is x km away, so I see what I see. I think what I'd see is a 'circle of flat land all around me. Still ok?

    So if my circle of flat land was a rubber mat that I could pick up and take elsewhere, why does it shrink/compress by the time I arrive at the pole? On a smooth sphere, surely my view of the distant horizon is the same at all points. Think of a large coin on a football. Centre of coin is you, edge of coin is your horizon. Slide you and the coin to any point on the football and your view of the horizon is the same.

    Posted

  • wassock by wassock moderator in response to AUricle's comment.

    What? If you a on the equator on earth on a boat mid atlantic then whichever way you look the horizon is 20 odd miles away. When the north polar cap melts and you sit in the boat some where inside the arctic circle the horizon is still the same distance away. Where ever you are you will still be sat on a big ball and its geometry will be the same wherever - just drawing a few lines on the surface doesnt change the distance to the horizon at any point. What does change is the distance between the lines of longitude as the latitude changes, at the equator, on earth the distance between each degree of longitude is about 69 miles, and the gets less and less the closer you get to the pole. And I think this is what Meg refers to.

    Edit - seems kith and I were both typing away at the same time.

    Posted

  • Kitharode by Kitharode moderator

    Undertype, overtype, wobberling free, three little wobberly martians are we.....etc.

    1deg Latitude on Earth = 111km (69 miles). 1deg Latitude on Mars = 60km (37 miles). In round numbers.

    Boats on oceans. That'll do nicely, so we agree on that. Also agree that Meg may simply be describing convergance of lat/long lines. I'm not sure why she would tell us that if the question is about scale, resolution, visual stuff. I need to backtrack a bit and reread some items.

    Does it have anything to do with an object in relation to curvature of the surface. Like when we view the Moon. Round craters in the middle of the image are round, but round craters near the edge are elliptical, as we see them more side-on?

    Posted

  • Kitharode by Kitharode moderator

    Just had a read through. AUricle's right - there's no answer to the question of magnification. Wait for a scientist? Or have you worked out what's happening?

    Posted

  • wassock by wassock moderator in response to Kitharode's comment.

    Not sure that the individual images, or even the larger HiRise pics cover enough ground for the curvature to have an effect. Where the problem lies is when you start pulling the images about to try and stitch them togehter so they'll line up. If you want a map showing a circle then you have to change the dimensions of the photos to make them fit so for a strip running equator to pole it has to be squeezed up as it tends to the pole. If you are going for a mercator projection, with parallel lines of longitude you have to widen the images as they approach the pole.

    Posted

  • wassock by wassock moderator in response to Kitharode's comment.

    So if you a looking at an image which has been fiddled with to make it fit into a map projection, then it may have been enlarged or reduced, depending on the type of projection, and the degree of the stretching or squishing will increase the closer you get to the pole

    ..... making good use of the spiders we find, stuff that the Martians have long left behind How sad is that?

    Posted

  • Kitharode by Kitharode moderator

    Thanks wassock. I absolutely get it. That was really well explained. So, just magnification then? (Not to be confused with just intonation).

    Posted

  • AUricle by AUricle in response to wassock's comment.

    Kith and wassock,

    Thanks for the splash of cold water. What I said about 'distance to horizon' was totally false. What is true about it is like what wassock said. You may see more degrees of lat/long, hoizon to horizon, and the circumference will shrink but the distance in mi.or km. will remain the same. So did I receive any answer at all?

    From Megs response, it sounds like we are not getting map projected images.( For our purposes, it would make no sense) So the stretching/squishing thing should not be in play, but I get what you were saying.

    There is one thing I'm wondering...and this often happens when you ask others to look at a particular image or featue. Do you guys see what I see as far as image #1 looking more distant than image #2?....even though #1 is "sharper" than #2, which is a resolution issue. Sometimes people "talk past each other" because they've interpreted the question slightly differently than the originator meant.

    Kith, that statement about yardangs blew me away. That goes against the theory of the katabatic winds being responsible, and the images clearly show ice on top of the yardangs......and if that's true, what the heck are we getting 'equatorial' images for, in a polar study?

    Posted

  • Kitharode by Kitharode moderator

    We're getting closer. Good stuff this is.

    For myself, no, I don't see more distant/less distant. What I see is long thin spiders in #1 totally in focus, with much bigger fatter lines of spiders in #2, but the focus is off a bit (it's icy, dusty, etc). Put another way, I've not photographed a tree at 50m, then photographed the tree at 20cm. What I've done is photo'd tree #1, then photo'd tree #2 from the same distance, but tree #2 is far bigger than #1. Hence the distance effect. But that's NOT fact of course.

    Yardangs. Yes, big surprise. Needs talking about. I also want to know more/gather together info on the katabatic wind. Be good if you could get your last paragraph onto my 'Yardangs - More Interesting...' thread so I could pick your brain there and leave here free for the image debate. It's in the Chat: Just Chatting section. Up to you.

    Posted

  • JellyMonster by JellyMonster in response to AUricle's comment.

    Do you guys see what I see as far as image #1 looking more distant than image #2?

    Yes, I do. You can get the same effect by zooming in on a random location in Google Maps. I really don't think the convergence of longitude lines has anything to do with it though . The more you pull away from the planet, image distortion will become more obvious (eventually you see it as a globe). But, if the photographs we see fill up only two rugby pitches (some look much further away), any distortion should be negligible.

    As you have probably guessed, scientific explanations are not my forte. Just think of me as a filler in 😃.

    Posted

  • mschwamb by mschwamb scientist, translator

    If you can give me APF numbers I can give you links to the HiRISE public pages and we can check the resolution. It could be the spacecraft was in closer orbit when it took one of those images hence more resolution.
    ~Meg

    Posted

  • Kitharode by Kitharode moderator in response to JellyMonster's comment.

    We're lucky then because scientific explanations are very much my forte. Unfortunately we're unlucky as well, because I get so many of them are wrong!! 😦 Still, two 'fillers' are better than none I reckon ... ?

    We've already visited a few HiRISE images and seen the 'data sheet' there. Wassock and others (you JM?) have been putting together 'side by side' images and finding nieghbours to the images, and it sounds like they've got some understanding of how image numbers relate, and how you find them. so maybe someone can post an 'everything you need to know about HiRise images' post somewhere. Be good for me...

    Posted

  • AUricle by AUricle in response to mschwamb's comment.

    Meg,

    I tried going into my collections to find the APF's of the images I posted, and I hit the "load more" button as many times as I could, but finally the screen just froze up and went black.( I got them up here because I'd saved the images to my HD but the ID # there is not the same as the APF #,and I guess there is no way to cross reference those?)

    I can't seem to get deep enough into my collection to find them without running into the 'freeze' problem. They are by far not the only images where I've noticed this 'distance' perception thing though, so I'll try again, and if I get stopped again, I should be able to come up with another suitable pair of images. Thanks for the offer. I'll get back to you as soon as I can come up with some APF's.

    Now the orbital altitude difference might be the answer. I'd sort of assumed imaging runs were more or less done from a standard alt., so all images would capture similar square areas.

    Posted

  • Kitharode by Kitharode moderator in response to AUricle's comment.

    AUricle. Before the info arrives, do you have any ideas / guesses about the distance of your 'distance anomaly', that is, when you look at your #1 and #2 images how much 'difference of altitude' do you feel might have occured?

    If there is a significant altitude difference in the orbiting camera (which we'll probably be able to work out from the HiRise pages) then it might be interesting to see how the truth of the matter compares with 'what we see'. You and JM lean towards the '#1 at 50m, #2 at 20cm' idea-ish, and I'm a 'same distance, #2 is bigger' advocate. In this case I'd be wrong.

    But if the camera altitude is 'pretty much' the same, we might both still be right/wrong and we'll have to find the answer elsewhere - in true citizen-science fashion, eh? Hope you understood all that...

    And am I right in thinking that, whatever the outcome, magnification may still be involved but not confirmed/denied?

    Posted

  • Kitharode by Kitharode moderator

    I'm sorry, I couldn't wait. In round figures and long story short...

    When MRO/HiRise arrived at Mars they were 'inserted' into a highly elliptical orbit: 426km to 44,500km from surface.

    BUT, there is a long aerobraking period to much more circular orbit: "In September 2006 MRO fired its thrusters twice more to fine-tune its final, nearly circular orbit to approximately 250 to 316 kilometres above the Martian surface. The SHARAD radar antennas were deployed on September 16. All of the scientific instruments were tested and most were turned off prior to the solar conjunction which occurred from October 7 to November 6, 2006. After the conjunction ended the "primary science phase" began".

    More details: http://en.wikipedia.org/wiki/Mars_Reconnaissance_Orbiter

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  • JellyMonster by JellyMonster

    Anya had stated somewhere in a blog, that the images are anywhere between 800m and 2000m across (my interpretation). That is a far bigger area than two rugby pitches!

    http://blog.planetfour.org/2013/01/15/you-have-asked/#comments

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