General Detection Penalties (Version 1.1)

General Detection Penalties (Version 1.1):

Introduction:
There are many factors that affect the ability for targets to be detected. The factors include vehicles hiding behind various terrains, the target being behind the horizon, and the radar absorbent materials of stealth aircraft. This addresses any of these but is meant for medium and larger vehicle. Individuals are much smaller targets and must be treated with caution although these rules and suggestions can be partially applies to them as well.

Read Sensory Instruments:
The author allows the skill of Read Sensory Instrument skill to be greater than 98%. The way these penalties were designed, if the read sensory skill instrument of an Individual or a system is about 98%, record how high above 98% the skill is and penalties are subtracted from that number and if the number still is above 98% then roll against 98%.

Terrain Penalties:
A common tactic for both aircraft and ground targets is to use the available terrain to reduce their chance of being detected. This table gives penalties for various types of terrain. Detect ambush skill can negate terrain penalties by detecting any damage to foliage or terrain, running and screaming people in cities, and disturbed animals. The negation of penalties by the detect ambush skill cannot be done at long range, by radar, or while moving fast. In most cases, the negation of penalties by the detect ambush skill cannot be done at night either. For calculating the penalties, do not add terrain penalties together, just use the highest terrain penalties. Visual penalties are based on the assumption that targets are of low visibility colors. Add a bonus to detection by visual means if this is not the case. Generally, visual detection without special equipment is virtually impossible over long distances but a full moon may allow some chance of detection through visual means.
No Line of Site: No chance of detection. This includes targets behind hill, mountains, and buildings.
Completely Hidden by Foliage or Trees: -50% detection penalty using radar (metal objects reflect more radar than trees) and no detection chance with visuals.
Mostly Hidden by Terrain: -50% detection penalty using radar or by visual means
Mostly hidden by Foliage or Trees: -35% detection penalty using radar (metal objects reflect more radar than trees) and -50% detection penalty using visual means of detection.
Partially Hidden by Terrain: -35% detection penalty using radar or by visual means.
Partially hidden by Foliage or Trees: -20% detection penalty using radar (metal objects reflect more radar than trees) and -35% detection penalty using visual means of detection.
Low Level over Rough Terrain: -20% detection penalty using radar or by visual means.
Low Level over Low Level Terrain with light Foliage: -10% detection penalty using radar (metal objects reflect more radar than trees) and -20% detection penalty using visual means of detection.

Weather Penalties:
The conditions of fog may also be applied for smoke or dust as appropriate to the conditions. These penalties are in addition to terrain penalties. Like terrain penalties, o not add various weather penalties together but instead use the highest penalties.
Light Rain / Light Fog: No detection penalty using radar (metal objects reflect more radar than water and water vapor) and -25% detection using normal visual means (some special optics will operate through rain and fog)
Moderate Rain / Moderate Fog: -10% detection penalty using radar (metal objects reflect more radar than water and water vapor) and -50% detection using normal visual means (some special optics will operate through rain and fog)
Heavy Rain / Heavy Fog: -20% detection penalty using radar (metal objects reflect more radar than water and water vapor) and -75% detection using normal visual means (some special optics will operate through rain and fog)
Very Heavy Rain /Very Heavy Fog: -30% detection penalty using radar (metal objects reflect more radar than water and water vapor) and no detection chance using normal visual means (some special optics will operate through rain and fog)

Line of Site:
Line of site for radar system is slightly longer than it is for visual means but listed below is a general table of line of site based on the height of objects. It has a minor amount of math but it is still relatively simple. It can be set up on a spreadsheet or using a scientific calculator quite easily.

Height is based on the observers eyes in feet above the ground to calculate distance to the horizon. To calculate for targets further above, you calculate the distance to the horizon for the observer and the calculate the distance to the horizon for the target. These two numbers are added together and you get the distance you can see the target.
For metric conversions

There are some other factors but they can be ignored for most role playing games. These are that there is a problem with the fact that light rays bend (refract) as they pass through water vapor. And, of course, there's more water vapor the closer you are to the sea surface. So, getting a range on a target that is over the horizon over water is pretty much hit or miss (pun intended). That's one of the reasons optical systems lose their accuracy the farther away they are from a target.

Modified Stealth Penalties:
Many vehicles are constructed out of material or have a coating of materials that absorb radar signals. These are very effective but there is a limitation that the stealth is less effective the closer the radar transmitter is to the target. This information is primarily listed for air vehicles but is also applicable to ground vehicle with a small amount of work. Most standard stealth aircraft have the same effectiveness as the Coalition Talon Stealth fighter which has a detection probability of -80% to be detected. Terrain penalties are also listed and they can be used for non stealth aircraft as well as stealth aircraft. The effects of terrain are determined by the position of the radar unit as well. A Radar transmitter in the air or on a high hill or mountain will allow for far better detection of targets.

Effects of Range:
If the target is from three quarters maximum to maximum range from radar transmitter, the penalty to detect targets has full penalties (-80% in the Coalition Talon and similar aircrafts case).
If the target is from half to three quarters maximum range from radar transmitter, the penalties to detect target has three quarters penalties (-60% in the Coalition Talon and similar aircrafts case).
If the target is from one quarter to half maximum range from radar transmitter, the penalties to detect target has half penalties (-40% in the Coalition Talon and similar aircrafts case).
If the target is less than one quarter of maximum range from radar transmitter, the penalties to detect target has one quarter penalties (-20% in the Coalition Talon and similar aircrafts case).

[ Coalition TM is a trademark owned by Kevin Siembieda and Palladium Books Inc. ]
[ Rifts® is a registered trademark owned by Kevin Siembieda and Palladium Books Inc.]

By Kitsune (E-Mail Kitsune).