{
  "id": 20589,
  "title": "This order or the reverse one?",
  "url": "/competitions/draper-satellite-image-chronology/discussion/20589",
  "author_name": "",
  "post_date": "2016-05-01T08:44:13.283Z",
  "votes": null,
  "comment_count": 4,
  "views": 1033,
  "content": "<p>Hi guys,</p>\n\n<p>does anyone have an idea how to determine if the order is\n<code>1 2 3 4 5</code>\nor the reverse one\n<code>5 4 3 2 1</code>\nLet's assume that you're sure that <code>1,2</code> and <code>2,3</code> and <code>3,4</code> and <code>4,5</code> are groups.</p>\n\n<p>Thanks for any ideas and good luck ;)</p>",
  "messages": [
    {
      "id": "117859",
      "postDate": "05/01/2016 08:44:13",
      "content": "<p>Hi guys,</p>\n\n<p>does anyone have an idea how to determine if the order is\n<code>1 2 3 4 5</code>\nor the reverse one\n<code>5 4 3 2 1</code>\nLet's assume that you're sure that <code>1,2</code> and <code>2,3</code> and <code>3,4</code> and <code>4,5</code> are groups.</p>\n\n<p>Thanks for any ideas and good luck ;)</p>",
      "rawMarkdown": "Hi guys,\r\n\r\ndoes anyone have an idea how to determine if the order is\r\n`1 2 3 4 5`\r\nor the reverse one\r\n`5 4 3 2 1`\r\nLet's assume that you're sure that `1,2` and `2,3` and `3,4` and `4,5` are groups.\r\n\r\nThanks for any ideas and good luck ;)",
      "votes": null
    },
    {
      "id": "117952",
      "postDate": "05/02/2016 01:10:07",
      "content": "<p>There are more than two orders. For each sample in the test set, you must predict the order that images 1,2,3,4,5 were taken. You then submit your predictions in a CSV file. But any order is possible eg. one set could be 2 3 1 5 4.</p>",
      "rawMarkdown": "There are more than two orders. For each sample in the test set, you must predict the order that images 1,2,3,4,5 were taken. You then submit your predictions in a CSV file. But any order is possible eg. one set could be 2 3 1 5 4.",
      "votes": null
    },
    {
      "id": "118405",
      "postDate": "05/03/2016 15:07:34",
      "content": "<p>I think the questioner is assuming that it's relatively easy (but still very hard!) to find shared features of images that imply an ordering in time (which could be 1,2,3,4,5 or 2,3,1,5,4 or any other); but relatively difficult to decide in which time direction that order applies.</p>\n\n<p>For example - let's say for a photo with a car park, there is a red car parked in the same spot for 3 out of the 5 photos, so you're relatively sure they can be grouped in time, then let's say there a different overlapping 3 photos where there is a blue car parked in the same spot and so on; so that you can build up a possible ordering based on many changes that group the photos together in time. With changes such as these, it's quite possible to have a good idea that the correct answer is either 1,2,3,4,5 or 5,4,3,2,1 but no way of knowing which (and guessing wrong many times would be disastrous)!</p>\n\n<p>I think the answer is that you will have to find types of changes that imply not only an order, but a time direction, such as tracks being laid down then wearing away slowly. A very difficult task given the different rotations, latitude of photo, zoom levels, lighting conditions, and all the changes which don't imply any kind of ordering like car positions on highways etc.</p>",
      "rawMarkdown": "I think the questioner is assuming that it's relatively easy (but still very hard!) to find shared features of images that imply an ordering in time (which could be 1,2,3,4,5 or 2,3,1,5,4 or any other); but relatively difficult to decide in which time direction that order applies.\r\n\r\nFor example - let's say for a photo with a car park, there is a red car parked in the same spot for 3 out of the 5 photos, so you're relatively sure they can be grouped in time, then let's say there a different overlapping 3 photos where there is a blue car parked in the same spot and so on; so that you can build up a possible ordering based on many changes that group the photos together in time. With changes such as these, it's quite possible to have a good idea that the correct answer is either 1,2,3,4,5 or 5,4,3,2,1 but no way of knowing which (and guessing wrong many times would be disastrous)!\r\n\r\nI think the answer is that you will have to find types of changes that imply not only an order, but a time direction, such as tracks being laid down then wearing away slowly. A very difficult task given the different rotations, latitude of photo, zoom levels, lighting conditions, and all the changes which don't imply any kind of ordering like car positions on highways etc.",
      "votes": null
    },
    {
      "id": "118406",
      "postDate": "05/03/2016 15:10:27",
      "content": "<p>Yes exactly! All in all it's a difficult challenge but well I'll try it just for fun ;)</p>",
      "rawMarkdown": "Yes exactly! All in all it's a difficult challenge but well I'll try it just for fun ;)",
      "votes": null
    },
    {
      "id": "118592",
      "postDate": "05/04/2016 12:42:26",
      "content": "<p>I can definitely say that it's important :D</p>\n\n<p>Moved up from -0,04 to 0,179 by reversing the list for about 50% of the set.</p>",
      "rawMarkdown": "I can definitely say that it's important :D\r\n\r\nMoved up from -0,04 to 0,179 by reversing the list for about 50% of the set.",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 117952,
      "author_name": "anokas",
      "author_url": "",
      "post_date": "05/02/2016 01:10:07",
      "content": "<p>There are more than two orders. For each sample in the test set, you must predict the order that images 1,2,3,4,5 were taken. You then submit your predictions in a CSV file. But any order is possible eg. one set could be 2 3 1 5 4.</p>",
      "votes": null,
      "replies": []
    },
    {
      "id": 118405,
      "author_name": "edwingraham",
      "author_url": "",
      "post_date": "05/03/2016 15:07:34",
      "content": "<p>I think the questioner is assuming that it's relatively easy (but still very hard!) to find shared features of images that imply an ordering in time (which could be 1,2,3,4,5 or 2,3,1,5,4 or any other); but relatively difficult to decide in which time direction that order applies.</p>\n\n<p>For example - let's say for a photo with a car park, there is a red car parked in the same spot for 3 out of the 5 photos, so you're relatively sure they can be grouped in time, then let's say there a different overlapping 3 photos where there is a blue car parked in the same spot and so on; so that you can build up a possible ordering based on many changes that group the photos together in time. With changes such as these, it's quite possible to have a good idea that the correct answer is either 1,2,3,4,5 or 5,4,3,2,1 but no way of knowing which (and guessing wrong many times would be disastrous)!</p>\n\n<p>I think the answer is that you will have to find types of changes that imply not only an order, but a time direction, such as tracks being laid down then wearing away slowly. A very difficult task given the different rotations, latitude of photo, zoom levels, lighting conditions, and all the changes which don't imply any kind of ordering like car positions on highways etc.</p>",
      "votes": null,
      "replies": []
    },
    {
      "id": 118406,
      "author_name": "wikunia",
      "author_url": "",
      "post_date": "05/03/2016 15:10:27",
      "content": "<p>Yes exactly! All in all it's a difficult challenge but well I'll try it just for fun ;)</p>",
      "votes": null,
      "replies": []
    },
    {
      "id": 118592,
      "author_name": "wikunia",
      "author_url": "",
      "post_date": "05/04/2016 12:42:26",
      "content": "<p>I can definitely say that it's important :D</p>\n\n<p>Moved up from -0,04 to 0,179 by reversing the list for about 50% of the set.</p>",
      "votes": null,
      "replies": []
    }
  ],
  "raw_markdown_by_id": {
    "117859": "Hi guys,\r\n\r\ndoes anyone have an idea how to determine if the order is\r\n`1 2 3 4 5`\r\nor the reverse one\r\n`5 4 3 2 1`\r\nLet's assume that you're sure that `1,2` and `2,3` and `3,4` and `4,5` are groups.\r\n\r\nThanks for any ideas and good luck ;)",
    "117952": "There are more than two orders. For each sample in the test set, you must predict the order that images 1,2,3,4,5 were taken. You then submit your predictions in a CSV file. But any order is possible eg. one set could be 2 3 1 5 4.",
    "118405": "I think the questioner is assuming that it's relatively easy (but still very hard!) to find shared features of images that imply an ordering in time (which could be 1,2,3,4,5 or 2,3,1,5,4 or any other); but relatively difficult to decide in which time direction that order applies.\r\n\r\nFor example - let's say for a photo with a car park, there is a red car parked in the same spot for 3 out of the 5 photos, so you're relatively sure they can be grouped in time, then let's say there a different overlapping 3 photos where there is a blue car parked in the same spot and so on; so that you can build up a possible ordering based on many changes that group the photos together in time. With changes such as these, it's quite possible to have a good idea that the correct answer is either 1,2,3,4,5 or 5,4,3,2,1 but no way of knowing which (and guessing wrong many times would be disastrous)!\r\n\r\nI think the answer is that you will have to find types of changes that imply not only an order, but a time direction, such as tracks being laid down then wearing away slowly. A very difficult task given the different rotations, latitude of photo, zoom levels, lighting conditions, and all the changes which don't imply any kind of ordering like car positions on highways etc.",
    "118406": "Yes exactly! All in all it's a difficult challenge but well I'll try it just for fun ;)",
    "118592": "I can definitely say that it's important :D\r\n\r\nMoved up from -0,04 to 0,179 by reversing the list for about 50% of the set."
  },
  "source": "meta"
}