{
  "id": 582630,
  "title": "ToF sensors explanation",
  "url": "/competitions/cmi-detect-behavior-with-sensor-data/discussion/582630",
  "author_name": "",
  "post_date": "2025-06-01T15:05:58.448332600Z",
  "votes": 4,
  "comment_count": 2,
  "views": 0,
  "content": "<p>Hello!</p>\n<p>Could you please explain in a bit more detail, what ToF sensors measure?<br>\n1) Are the values in the resulting 2d arrays monotonicly related to distance to the object (larger sensor values mean larger distance)? Is there a formula to convert sensor values to distances?<br>\n2) If we look at the arm picture on the Overview page, do these sensors measure distance from the watch to us (observers), or from the watch to the parts of the arm they're on? (I guess the first)</p>",
  "messages": [
    {
      "id": "3215091",
      "postDate": "06/01/2025 15:05:58",
      "content": "<p>Hello!</p>\n<p>Could you please explain in a bit more detail, what ToF sensors measure?<br>\n1) Are the values in the resulting 2d arrays monotonicly related to distance to the object (larger sensor values mean larger distance)? Is there a formula to convert sensor values to distances?<br>\n2) If we look at the arm picture on the Overview page, do these sensors measure distance from the watch to us (observers), or from the watch to the parts of the arm they're on? (I guess the first)</p>",
      "rawMarkdown": "Hello!\n\nCould you please explain in a bit more detail, what ToF sensors measure?\n1) Are the values in the resulting 2d arrays monotonicly related to distance to the object (larger sensor values mean larger distance)? Is there a formula to convert sensor values to distances?\n2) If we look at the arm picture on the Overview page, do these sensors measure distance from the watch to us (observers), or from the watch to the parts of the arm they're on? (I guess the first)",
      "votes": null
    },
    {
      "id": "3216527",
      "postDate": "06/03/2025 17:49:58",
      "content": "<p>1) They are the aboslute distances in mm I believe. After going through the documentation for the sensor provide in the data page this is what I found:</p>\n<blockquote>\n  <p>Like all Time-of-Flight (ToF) sensors based on ST's FlightSense technology, the VL53L7CX records, in each zone,<br>\n  an absolute distance regardless of the target color and reflectance.</p>\n</blockquote>\n<p>2)Yes the sensors are facing outside, so measure distance to us. If the palm is facing the head of the wearer, it will give the approx distance to the head.</p>",
      "rawMarkdown": "1) They are the aboslute distances in mm I believe. After going through the documentation for the sensor provide in the data page this is what I found:\n> Like all Time-of-Flight (ToF) sensors based on ST's FlightSense technology, the VL53L7CX records, in each zone,\nan absolute distance regardless of the target color and reflectance.\n\n2)Yes the sensors are facing outside, so measure distance to us. If the palm is facing the head of the wearer, it will give the approx distance to the head.",
      "votes": null
    },
    {
      "id": "3216640",
      "postDate": "06/03/2025 21:57:48",
      "content": "<p>Thank you for your answer!</p>\n<p>I've overlooked for some reason that there was a documentation attached. :)</p>\n<p>Given the sensor distance measurement range, I agree about the second point.</p>\n<p>I am not sure about the first point, because the sensor does measure distance, however, the raw values could be some signal strength values or some distance-like values (in the first case, larger values imply smaller distance, in the second case it's the opposite). The distances one would, I think, definitely get as the output of the sensor's driver.</p>\n<p>I asked about conversion to distances, because having distances could possibly give a bit more understanding of possible feature engineering…</p>",
      "rawMarkdown": "Thank you for your answer!\n\nI've overlooked for some reason that there was a documentation attached. :)\n\nGiven the sensor distance measurement range, I agree about the second point.\n\nI am not sure about the first point, because the sensor does measure distance, however, the raw values could be some signal strength values or some distance-like values (in the first case, larger values imply smaller distance, in the second case it's the opposite). The distances one would, I think, definitely get as the output of the sensor's driver.\n\nI asked about conversion to distances, because having distances could possibly give a bit more understanding of possible feature engineering...",
      "votes": null
    }
  ],
  "comments": [
    {
      "id": 3216527,
      "author_name": "abhirupchoudhury073",
      "author_url": "",
      "post_date": "06/03/2025 17:49:58",
      "content": "<p>1) They are the aboslute distances in mm I believe. After going through the documentation for the sensor provide in the data page this is what I found:</p>\n<blockquote>\n  <p>Like all Time-of-Flight (ToF) sensors based on ST's FlightSense technology, the VL53L7CX records, in each zone,<br>\n  an absolute distance regardless of the target color and reflectance.</p>\n</blockquote>\n<p>2)Yes the sensors are facing outside, so measure distance to us. If the palm is facing the head of the wearer, it will give the approx distance to the head.</p>",
      "votes": null,
      "replies": [
        {
          "id": 3216640,
          "author_name": "tayken",
          "author_url": "",
          "post_date": "06/03/2025 21:57:48",
          "content": "<p>Thank you for your answer!</p>\n<p>I've overlooked for some reason that there was a documentation attached. :)</p>\n<p>Given the sensor distance measurement range, I agree about the second point.</p>\n<p>I am not sure about the first point, because the sensor does measure distance, however, the raw values could be some signal strength values or some distance-like values (in the first case, larger values imply smaller distance, in the second case it's the opposite). The distances one would, I think, definitely get as the output of the sensor's driver.</p>\n<p>I asked about conversion to distances, because having distances could possibly give a bit more understanding of possible feature engineering…</p>",
          "votes": null,
          "replies": []
        }
      ]
    }
  ],
  "raw_markdown_by_id": {
    "3215091": "Hello!\n\nCould you please explain in a bit more detail, what ToF sensors measure?\n1) Are the values in the resulting 2d arrays monotonicly related to distance to the object (larger sensor values mean larger distance)? Is there a formula to convert sensor values to distances?\n2) If we look at the arm picture on the Overview page, do these sensors measure distance from the watch to us (observers), or from the watch to the parts of the arm they're on? (I guess the first)",
    "3216527": "1) They are the aboslute distances in mm I believe. After going through the documentation for the sensor provide in the data page this is what I found:\n> Like all Time-of-Flight (ToF) sensors based on ST's FlightSense technology, the VL53L7CX records, in each zone,\nan absolute distance regardless of the target color and reflectance.\n\n2)Yes the sensors are facing outside, so measure distance to us. If the palm is facing the head of the wearer, it will give the approx distance to the head.",
    "3216640": "Thank you for your answer!\n\nI've overlooked for some reason that there was a documentation attached. :)\n\nGiven the sensor distance measurement range, I agree about the second point.\n\nI am not sure about the first point, because the sensor does measure distance, however, the raw values could be some signal strength values or some distance-like values (in the first case, larger values imply smaller distance, in the second case it's the opposite). The distances one would, I think, definitely get as the output of the sensor's driver.\n\nI asked about conversion to distances, because having distances could possibly give a bit more understanding of possible feature engineering..."
  },
  "source": "meta"
}