Difference between revisions of "UFO Detection"

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(→‎Losing Contact: removing added statement that I am fairly certain is wrong, will move to chat to discuss)
(near-full rewrite; almost done, safety save)
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Alien craft regulary enter and leave the Earth's atmosphere. Spotting them and shooting them down is an important goal. Before you worry about [[UFO Interception|shooting them down]], first you have to spot them, so you will need to know how to go about this.
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Alien craft regularly enter and leave the Earth's atmosphere. In order to prevent them from carrying out their missions, you [[UFO Interception|shoot them down]] or [[UFO Ground Assault|assault them while landed]].  However, in order to perform either of these tasks, you must first spot them.
  
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==Detection Facilities==
  
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==Types of Detection Facilities==
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Three types of UFO detectors can be built on your bases:
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* [[Small Radar]]
 
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* [[Large Radar]]
 
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* [[Hyper-Wave Decoder]]
 
  
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The above can be built in your base for the purpose of detecting UFOs nearby. Also all your craft have shorter range radars that can be used to keep contact when chasing a UFO or to sweep an area for either ground based or aerial targets.
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*[[Small Radar]]s have a range of 300 nautical miles (nm) according to the UFOpaedia.  However, this figure is too short by a factor of five.  The Official Strategy Guide gives the figure as 1500 nm, which matches what has been obsered in-game. 
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*[[Large Radar]]s have a detection range of 450 nm according to the UFOpaedia; their actual range is 2250 nm.  Large radars cover 225% the total area of small radars (1.5x radius translates into 2.25x area).  
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*[[Hyper-Wave Decoder]]s do not have a detection range listed in the UFOpaedia, but both the OSG and observation show that they have a range of 2400 nm, slightly larger than that of a Large Radar.
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*All X-COM craft have an observed detection range of approximately 700 nm (possibly 750 nm).
  
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==Radars==
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Your first base starts out with a Small Radar; you can choose to add a Large Radar as well, which will take 24 days to build.  Both radar types can also be added to any other base you establish.  Hyper-Wave Decoders can only be built after you have captured an alien Navigator.  [[Research]]ing the navigator unlocks a "Hyper-Wave Decoder" topic; after it is researched, you can build Hyper-Wave Decoders at any of your bases.
  
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Small Radars cover 300 nautical miles according to the UFOpedia, but in practise the radius that you can track out to equates to approximately the distance between Budapest and Reykjavik, which my atlas tells me is closer to 2000 miles. Detection seems to only occur in a smaller radius, of perhaps 1300-1500 miles. Inside this detection radius they have a base 10% detection chance which is tested every 30 minutes exactly on the half hour, so if you are advancing the game an hour or day at a time you may find it jumps forward to exactly a half hour interval as it spots a new UFO. Building more than one Small Radar does not increase your detection rate, despite it making it look this way in the base information screen.
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===Range Diagrams===
  
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Large Radars cover 450 nautical miles according to the UFOpedia, it is unknown what this translates to, but it seems reasonable from inference and experience to assume it will be about 3000 miles. Note this translates to a 125% increase in land area covered (as long as it is 150% of the radius, it will be 225% of the area anyway). In line with Small Radars detection is more difficult, so only will pick up new contacts from around 2000-2300 miles. Inside this detection radius they have a base 20% detection chance which is tested every 30 minutes exactly on the half hour, so if you are advancing the game an hour or day at a time you may find it jumps forward to exactly a half hour interval as it spots a new UFO. Building more than one Large Radar does not increase your detection rate, despite it making it look this way in the base information screen.
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The following graphic shows the range of each type of radar system:
  
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Large and Small radars add together, so if you have one of each you get 30% short range and 20% long range detection, until you get Hyperwave Decoders available you might consider building one of each in every base that you want to be detecting aliens for maximum coverage, but any more is a waste.
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[[Image:Detection and tracking ranges.png]]
  
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Note that the radius of detection (but not tracking) and/or the detection chance ''might'' be affected by the size of the UFO being searched for, the UFOpedia suggests it has an impact, but this needs to be determined whether it does actually play a part.
 
  
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==Hyperwave Decoder==
 
  
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A high priority [[research]] item, these devices obsolete all radars as not only do they have at least as large a range as Large Radars, they work 100% of the time, so you always know when an alien has entered your airspace (for any base with a Decoder, anyway) whenever the first 30 minute detection check comes by and they are still there. Very fast UFOs might still pass through some of your airspace without being detected, if they do it in between checks. The Decoder also provides essential strategic and tactical information about the craft, its mission, and destination etc. All this makes these facilities absolutely critical to your mission.
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== How Radars Function ==
  
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==Craft Radars==
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Each radar type has a chance to detect any UFO within its range.  Detections are performed in the game every 30 minutes exactly on the half hour.  (If you are advancing the game an hour or day at a time, you may find the clock jumps forward to exactly a half hour interval whenever it spots a new UFO.)
  
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Your craft can also detect UFOs via onboard scanners, these seem to have a range of roughly 500 miles, but they do seem to have quite a high detection rate - maybe even 100%. If an alien vessel moves out of range of your land-based detection systems, you may be able to resume tracking by sending one of your ships to where you believe the UFO to be (based on its speed and direction). Craft Radars are also key to locating enemy based, and might be used for spotting landed craft, or scouting areas that are showing high UFO activity in the Graphs section.
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Small Radars have a 10% chance of detecting UFOs within their range, and Large Radars have a 20% chance. If you have both Small and Large Radars built at the same base, their abilities are added together: you will have a 30% chance of detecting UFOs within 1500 nm and a 20% chance of detecting UFOs from 1500 nm to 3000 nm.
  
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Note that ground based radar are poor at detecting landed craft (and dont seem to spot bases at all), where craft can usually find these quite quickly if in the relative small radar area it has. Hyperwave Decoders dont detect bases directly either, but because they are so good at spotting any craft in a large area, and their mission profile, it makes it quickly evident if and where any alien bases are located.
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Despite the "Short Range" and "Long Range" detection bars displayed on each base's Information screen, only one radar of each type will be used at each base; building additional radars will have no effect.
  
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==Losing Contact==
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Hyper-Wave Decoders have a 100% chance of detecting any UFOs within their range.  Given their superior range and detection abilities, Hyper-Wave Decoders make the other radar types unnecessary.  If you have Small or Large Radars in a base which also has a decoder, you can dismantle them. 
  
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In most cases you will continue to see a detected UFO until it is outside any of your radar ranges (craft or land based) at a half hour checkpoint. In a few cases they will dissappear off radar at times other than the half hour, this might be when an alien craft decides to end its mission and leave the atmosphere, but there may be something else at play.
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"Normal" radars reveal the approximate size, altitude, heading, and speed of UFOs within range.  Hyper-Wave Decoders display the exact craft type, the alien race onboard, what type of mission the UFO is on, and where the mission is to be performed.
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{| width = "60%" align = "center" style = "border: 1px solid; border-collapse:collapse;"
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|+ Table 1: Radar Ability Combinations
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|- style = "font-size:larger; font-weight: bold; border-bottom: 1px black solid; background: gray; color:white;"
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| Radar Module / Scan Type || Short || Long || Hyperwave
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|- style = ""
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| Small Radar || 10 || 0 || 0
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|-
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| Large Radar || 20 || 20 || 0
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|-
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| Hyperwave || 0 || 0 || 100
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|- colspan = "4" style = "border-top: 1px dotted; font-wight: bold;"
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| Radar Combinations
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|- style = "background: #EEE;"
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| Sm + Sm || 10 || 0 || 0
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|-
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| Sm + Lg || 30 || 20 || 0
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|-style = "background: #EEE;"
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| Sm + Hyp || 10 || 0 || 100
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|-
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| Lg + Lg || 20 || 20 || 0
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|-style = "background: #EEE;"
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| Lg + Hyp || 20 || 20 || 100
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|-
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| Hyp + Hyp || 0 || 0 || 100
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|-style = "background: #EEE;"
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| Sm + Lg + Hyp || 30 || 20 || 100
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|}
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''These figures were derived from values found in save-game files.''
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Once a UFO has been spotted, it will remain on your radar until it drops out of tracking range or leaves the atmosphere altogether.  Due to the delay caused by the game's half-hour "detection updates", UFOs will often first be detected well within a radar's maximum range, and tracked far beyond the radar's normal maximum.  This is especially true for fast-moving UFOs, which can travel as much as 2500 nm between updates.
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== Craft-based UFO Detection ==
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All airborne X-COM craft, whether en route or patrolling, can also detect UFOs within a small range, which testing has shown to be 700 to 750 nm.  Within this range, craft can detect UFOs 100% of the time.  However, given the half-hour detection update intervals and both UFO and craft speed, UFOs can often pass within range of an X-COM craft without being spotted.  All types of craft, whether [[Skyranger]]s or [[Avenger]]s, have the same detection radius.  Faster craft may sometimes appear to have a shorter detection radius, as they can travel great distances between detection updates.
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If an alien vessel moves out of range of your land-based detection systems, you may be able to resume tracking by sending one of your ships to where you believe the UFO to be (based on its speed and direction).  
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=== Alien Base Detection ===
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All X-COM craft are also capable of detecting alien bases.  In fact, this is the only way to discover aliens bases: they will not show up on any base radar, including Hyper-Wave Decoders.  In order to discover an alien base, an X-COM craft must patrol within 1500 nm of the base's location.  The nearer the craft, the sooner the base will be discovered.  Patrolling immediately above a base will reveal it almost immediately; patrolling 1500 nm away, the base may take one hour to discover, or several hours.
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Bases can only be discovered by ''patrolling'' craft.  An X-COM craft could fly over an alien base repeatedly and never discover it until it began patrolling in the area.
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It is frequently possible to deduce where an alien base is by the pattern of UFO traffic.  The primary mission of [[Supply Ship]]s is to supply alien bases; wherever they land, a base is likely to be found.  When a base is first being built, four UFOs (a scout, two supply ships, and a battleship) will converge upon the same area and mill around for a while.  The alien race found at the base (if built) will always be of the same type as the race found on these ships (or the supply ships which subsequently show up at regular intervals).
  
 
==UFO Activity Graph==
 
==UFO Activity Graph==
  
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Finally, the UFO activity graphs act as a sort of MUFON, allowing you to see activity that your radars cannot.  The graphs are updated every 30 minutes, on the half hour.  You could even check the graphs every so often and build zero radars if you wanted, and if you see a blip, send aircraft.  This worldwide coverage can be easily used this way for the first few months.  After that, UFO activity becomes too intense and the graphs lose their resolution, but by that time you should aim to have decoders already built, or on the way.
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Finally, the UFO activity graphs can act as a sort of "MUFON" (a civilian group dedicated to the observation of UFOs), allowing you to see activity that your radars cannot.  The graphs are updated every 30 minutes, on the half hour.  You could even check the graphs every so often and build zero radars if you wanted, and if you see a blip, send aircraft.  This worldwide coverage can be easily used this way for the first few months.  After that, UFO activity becomes too intense and the graphs lose their resolution, but by that time you should aim to have decoders already built, or on the way.
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The graph is of particular use for discovering where alien bases have been built; these locations always show a very high degree of alien activity.

Revision as of 05:34, 2 March 2007

Alien craft regularly enter and leave the Earth's atmosphere. In order to prevent them from carrying out their missions, you shoot them down or assault them while landed. However, in order to perform either of these tasks, you must first spot them.

Detection Facilities

Three types of UFO detectors can be built on your bases:

  • Small Radars have a range of 300 nautical miles (nm) according to the UFOpaedia. However, this figure is too short by a factor of five. The Official Strategy Guide gives the figure as 1500 nm, which matches what has been obsered in-game.
  • Large Radars have a detection range of 450 nm according to the UFOpaedia; their actual range is 2250 nm. Large radars cover 225% the total area of small radars (1.5x radius translates into 2.25x area).
  • Hyper-Wave Decoders do not have a detection range listed in the UFOpaedia, but both the OSG and observation show that they have a range of 2400 nm, slightly larger than that of a Large Radar.
  • All X-COM craft have an observed detection range of approximately 700 nm (possibly 750 nm).

Your first base starts out with a Small Radar; you can choose to add a Large Radar as well, which will take 24 days to build. Both radar types can also be added to any other base you establish. Hyper-Wave Decoders can only be built after you have captured an alien Navigator. Researching the navigator unlocks a "Hyper-Wave Decoder" topic; after it is researched, you can build Hyper-Wave Decoders at any of your bases.

Range Diagrams

The following graphic shows the range of each type of radar system:

Detection and tracking ranges.png


How Radars Function

Each radar type has a chance to detect any UFO within its range. Detections are performed in the game every 30 minutes exactly on the half hour. (If you are advancing the game an hour or day at a time, you may find the clock jumps forward to exactly a half hour interval whenever it spots a new UFO.)

Small Radars have a 10% chance of detecting UFOs within their range, and Large Radars have a 20% chance. If you have both Small and Large Radars built at the same base, their abilities are added together: you will have a 30% chance of detecting UFOs within 1500 nm and a 20% chance of detecting UFOs from 1500 nm to 3000 nm.

Despite the "Short Range" and "Long Range" detection bars displayed on each base's Information screen, only one radar of each type will be used at each base; building additional radars will have no effect.

Hyper-Wave Decoders have a 100% chance of detecting any UFOs within their range. Given their superior range and detection abilities, Hyper-Wave Decoders make the other radar types unnecessary. If you have Small or Large Radars in a base which also has a decoder, you can dismantle them.

"Normal" radars reveal the approximate size, altitude, heading, and speed of UFOs within range. Hyper-Wave Decoders display the exact craft type, the alien race onboard, what type of mission the UFO is on, and where the mission is to be performed.

Table 1: Radar Ability Combinations
Radar Module / Scan Type Short Long Hyperwave
Small Radar 10 0 0
Large Radar 20 20 0
Hyperwave 0 0 100
Radar Combinations
Sm + Sm 10 0 0
Sm + Lg 30 20 0
Sm + Hyp 10 0 100
Lg + Lg 20 20 0
Lg + Hyp 20 20 100
Hyp + Hyp 0 0 100
Sm + Lg + Hyp 30 20 100

These figures were derived from values found in save-game files.

Once a UFO has been spotted, it will remain on your radar until it drops out of tracking range or leaves the atmosphere altogether. Due to the delay caused by the game's half-hour "detection updates", UFOs will often first be detected well within a radar's maximum range, and tracked far beyond the radar's normal maximum. This is especially true for fast-moving UFOs, which can travel as much as 2500 nm between updates.

Craft-based UFO Detection

All airborne X-COM craft, whether en route or patrolling, can also detect UFOs within a small range, which testing has shown to be 700 to 750 nm. Within this range, craft can detect UFOs 100% of the time. However, given the half-hour detection update intervals and both UFO and craft speed, UFOs can often pass within range of an X-COM craft without being spotted. All types of craft, whether Skyrangers or Avengers, have the same detection radius. Faster craft may sometimes appear to have a shorter detection radius, as they can travel great distances between detection updates.

If an alien vessel moves out of range of your land-based detection systems, you may be able to resume tracking by sending one of your ships to where you believe the UFO to be (based on its speed and direction).

Alien Base Detection

All X-COM craft are also capable of detecting alien bases. In fact, this is the only way to discover aliens bases: they will not show up on any base radar, including Hyper-Wave Decoders. In order to discover an alien base, an X-COM craft must patrol within 1500 nm of the base's location. The nearer the craft, the sooner the base will be discovered. Patrolling immediately above a base will reveal it almost immediately; patrolling 1500 nm away, the base may take one hour to discover, or several hours.

Bases can only be discovered by patrolling craft. An X-COM craft could fly over an alien base repeatedly and never discover it until it began patrolling in the area.

It is frequently possible to deduce where an alien base is by the pattern of UFO traffic. The primary mission of Supply Ships is to supply alien bases; wherever they land, a base is likely to be found. When a base is first being built, four UFOs (a scout, two supply ships, and a battleship) will converge upon the same area and mill around for a while. The alien race found at the base (if built) will always be of the same type as the race found on these ships (or the supply ships which subsequently show up at regular intervals).

UFO Activity Graph

Finally, the UFO activity graphs can act as a sort of "MUFON" (a civilian group dedicated to the observation of UFOs), allowing you to see activity that your radars cannot. The graphs are updated every 30 minutes, on the half hour. You could even check the graphs every so often and build zero radars if you wanted, and if you see a blip, send aircraft. This worldwide coverage can be easily used this way for the first few months. After that, UFO activity becomes too intense and the graphs lose their resolution, but by that time you should aim to have decoders already built, or on the way.

The graph is of particular use for discovering where alien bases have been built; these locations always show a very high degree of alien activity.

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