{"action":"created","issue":{"url":"https://api.github.com/repos/daid/EmptyEpsilon/issues/14","labels_url":"https://api.github.com/repos/daid/EmptyEpsilon/issues/14/labels{/name}","comments_url":"https://api.github.com/repos/daid/EmptyEpsilon/issues/14/comments","events_url":"https://api.github.com/repos/daid/EmptyEpsilon/issues/14/events","html_url":"https://github.com/daid/EmptyEpsilon/issues/14","id":58370490,"number":14,"title":"Sensor fingerprints for space objects","user":{"login":"IvanSanchez","id":1125786,"avatar_url":"https://avatars.githubusercontent.com/u/1125786?v=3","gravatar_id":"","url":"https://api.github.com/users/IvanSanchez","html_url":"https://github.com/IvanSanchez","followers_url":"https://api.github.com/users/IvanSanchez/followers","following_url":"https://api.github.com/users/IvanSanchez/following{/other_user}","gists_url":"https://api.github.com/users/IvanSanchez/gists{/gist_id}","starred_url":"https://api.github.com/users/IvanSanchez/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/IvanSanchez/subscriptions","organizations_url":"https://api.github.com/users/IvanSanchez/orgs","repos_url":"https://api.github.com/users/IvanSanchez/repos","events_url":"https://api.github.com/users/IvanSanchez/events{/privacy}","received_events_url":"https://api.github.com/users/IvanSanchez/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/daid/EmptyEpsilon/labels/enhancement","name":"enhancement","color":"84b6eb"}],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":3,"created_at":"2015-02-20T15:49:32Z","updated_at":"2015-02-21T17:36:17Z","closed_at":null,"body":"This is an idea from playing too much Allegiance and UFO Afterlight, and from working with real radar&lidar systems.\r\n\r\nThe sensors system is quite naïve: a spaceObject is either seen or not seen, and \"sensors\" is just one monolithic system. In real life, targets are acquired by aggregating input from several sensor systems: radar, lidar, AIS, FoF, cameras, and what-have-you.\r\n\r\nAlso, some objects (e.g. planets, stations) are more difficult to detect than others (fighter ships). This is the sensor fingerprint.\r\n\r\nI don't want to reinvent the Science UI but rather set foundations for this.\r\n\r\nSo every space object should have several attributes:\r\n\r\n- Mass, measured in tons. Massive objects will show up in gravimetric sensors (and, yes, gravimetry is a real thing https://en.wikipedia.org/wiki/Gravimetry ).\r\n- Reflectivity, measured in percent. AKA \"if I throw some radiation at the thing, how much will I get back?\". Rough surfaces (planets) have high reflectivity, and stealth ships have low reflectivity. Active sensors (such as radar) operate under this concept.\r\n- Radiance, measured in watts. AKA \"how much energy is the thing passively emitting away\". Shielded spaceships should have low radiance. Things like warping and firing beams would momentarily increase radiance. Passive sensors (such as video cameras) operate under this concept.\r\n- Psi, AKA \"intelligent lifeforms\", measured in sapiens (1 sapien = the brain of a standard homo sapiens). Futuristic alien sensors might be able to detect Psi, because UFO Afterlife had \"Psi Vision\" http://www.ufo-afterlight.com/images/scr_10.jpg . And maybe some aliens are attracted/repelled by Psi.\r\n\r\nIf we want to go crazy, radiance and reflectivity can be split into several parts of the EM spectrum: microwave, visible and x-ray.\r\n\r\nI just want my science officer to yell \"Contacts in the gravimetric sensor, activating microwave emitters!\" :-)\r\n"},"comment":{"url":"https://api.github.com/repos/daid/EmptyEpsilon/issues/comments/75382495","html_url":"https://github.com/daid/EmptyEpsilon/issues/14#issuecomment-75382495","issue_url":"https://api.github.com/repos/daid/EmptyEpsilon/issues/14","id":75382495,"user":{"login":"IvanSanchez","id":1125786,"avatar_url":"https://avatars.githubusercontent.com/u/1125786?v=3","gravatar_id":"","url":"https://api.github.com/users/IvanSanchez","html_url":"https://github.com/IvanSanchez","followers_url":"https://api.github.com/users/IvanSanchez/followers","following_url":"https://api.github.com/users/IvanSanchez/following{/other_user}","gists_url":"https://api.github.com/users/IvanSanchez/gists{/gist_id}","starred_url":"https://api.github.com/users/IvanSanchez/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/IvanSanchez/subscriptions","organizations_url":"https://api.github.com/users/IvanSanchez/orgs","repos_url":"https://api.github.com/users/IvanSanchez/repos","events_url":"https://api.github.com/users/IvanSanchez/events{/privacy}","received_events_url":"https://api.github.com/users/IvanSanchez/received_events","type":"User","site_admin":false},"created_at":"2015-02-21T17:36:17Z","updated_at":"2015-02-21T17:36:17Z","body":"> Most important detail is on how to go from \"sensors say x\" to, \"ok, this is a destroyer from race Y at position Z\"\r\n\r\nEasy. Targets are identified when sensor measurements go over a threshold. The threshold depends on background noise and sensor sensitivity.\r\n\r\nIn real-life radar, you listen for microwaves coming in, but most of the stuff is just background noise. If you're lucky and a target is emmitting microwaves like crazy, you'll see it over the background noise. Usually you'll throw microwaves around, and if a target reflects them well enough, you'll see the reflection over the background noise.\r\n\r\nI think all sensor bands (gravimetric, µwave, visible, x-ray, psi) can operate under the same principle, something simple like:\r\n\r\n```\r\nsignature = target_radiance + sensor_power * target_reflectivity;\r\nif ( signature / distance^2 - background_noise > sensor_threshold) {\r\n  // target_detected\r\n}\r\n```\r\n\r\nI think that sensors should have a couple of defined thresholds - for displaying a blip, tracking it and identifying a target. That keeps them simple enough.\r\n\r\nThe hardcore way of doing this would be to going full nerdy into decibels and emulating the statistical analysis for establishing confidence values of detection, but I think that'd only overcomplicate things.\r\n\r\nAnd for gravimetric sensors, radiance would be equal to the momentum (remember to add rotational momentum, so black holes show up easily). Grav sensors are only passive, and the own ship's momentum counts toward the background noise. Or maybe grav sensors can be active if the ship can do a \"warp ping\" or something.\r\n\r\nA nice thing to do would be to mask a sensor signature by its nearby sensor signatures. Usually, when a radar blip is big enough, you can't know if there's one ship or two ships together (doing a docking maneuver or whatever). I mean, who wouldn't like to hide a ship next to a black hole?\r\n\r\nAnyway, enough daydreaming. Please add a concept of sensor bands (grav, µwave, visible, xray, psi) and reflectivity/radiance attributes to every spaceObject. I guess sensor logic is a separate matter :-)"}}