About pressure and altimeter at Real World Edit
Since Second Life does not have climatology (atmospheric pressure, temperature or wind among others), although they can be simulated for specific cases (for example, sailing in their tournaments uses a standard wind script for that all boats to be in the same conditions when making a race), the concept "altimetry" has to adapt to the circumstances of a virtual world.
But before talking about how altitude is measured in Second Life, I will indicate the use in the real aviation of the altimeter, a very interesting instrument that is only a barometer modified to measure the altitude in meters or feet about sea level (ASL), which is called standard atmosphere and whose pressure is 1013 mb per cm2; within this idea, we know that the pressure decreases with increasing height (specifically, 1mb every nine meters); in addition, to know that the temperature affects the pressure, with which the calculations are very complex.
QNH, QFE and QNE Edit
In order not to complicate matters, just say that there are three concepts that apply both in real aviation and in Second Life aviation: the altitude of an airport about sea level (QNH), altitude above standard sea level (QNE) and the altitude about ground Level (QFE). This means that we have an altitude measurement of the airport at the level of the runway, another that indicates the altitude at which we are on the surface of the water, and another that indicates the altitude of the land just below the aircraft (plains, hills, valleys or mountains). For each moment of the flight we must have activated one of these altimeters, namely: when we take off or landing at an airport we will use the airport QNH (If you have the altitude of the land where the airport is, you can also use QFE); if we fly to a high altitude, away from the highest mountain, we would use the QNE (with this altimeter the flight level or FL is controlled); and if we fly to low altitude, near possible orographic accidents, we would use the QFE (see illustration on the left).
ATTENTION: we must remember to put the QNH to our height from the plane cabin, adding it to the QNH; imagine that we are going in a Cessna type plane, being the height very small from our center of mass to the runway (around 2m), so if the QNH of the airport is 25m, when added it would be 27m; if we go on a big Airbus type plane, we could be almost 8m from the runway; to calculate all this, we just have to put the planes we usually use on a firm base where we can do rez, and get on each one, putting them in physical mode deactivating the brake, being in that moment when we take the measurement.
Second Life measures Edit
In Second Life there are also three types of altitudes, and the most important being that we can find in the large map, marked as coordinates of the region where we are (we can also see it in the upper tab, where information comes from the region and the plot); the coordinates are indicated by three reference points or three-dimensional (X, Y and Z, which would be the same as for an object the length, width and height): the "X" is the point that would indicate the position EAST - WEST of the region (the longitude if we look at it as the reference point of the whole grid), the "Y" is the point that would indicate the NORTH - SOUTH position of the region (the latitude in this case), and the "Z" would be the absolute altitude of an object or avatar within Second Life (the maximum altitude is 4096 meters or 16 height sims, unable to fly with any aircraft above this limit, since it disappears and we receive a message indicating that "we have left the limits of the world ").
The altitudes that we can find in Second Life are: the one already indicated as ABSOLUTE, which is the one that marks our real altitude within the grid (taken from the center of mass of the avatar, which is half of its height, being in my case of 1.87 meters, that is, 0.935 meters mass center, or one meter if we round it); the altitude above sea level or ASL, which is established over 20 meters (although it is the standard, there are areas on the continent of Sansara whose sea level is 80 meters, for example Sutherland Abyss), but remains as a standard level for flight effects since using a mathematical function that gives us sea level, always part of zero meters regardless of depth (see the image to the left how example); and the altitude about ground level or AGL, which will always vary below us, when we fly over a valley or near mountains (we need remember that people who put lines of prohibition almost always establish them at 100 meters from height, so we always have to fly in elevated areas to 100 meters above AGL).
Flight Instruments with HUD: Altimeters Edit
For most pilots in Second Life, the biggest concern is have excese of scripts while flying, which often causes a lot of lag when crossing the sims and having crashes; already many scripts usually have the airplane, helicopter or other vehicle that we use to have more instruments how HUDs (Head Up Display) type; at a particular level, I prefer more "to have the security of knowledge than the tranquility of ignorance", that is, I prefer to use certain instruments that make me visible on a "radar" and for those who use or see it (such as SA - Transponder - v1.1), or other that indicate that I approach conflict zones with ban lines or similar (Ban Line HUD V5) and, of course, an instrument that accurately indicates several elements such as altitude, speed, inclination of the vehicle, direction, proximity of a region cross, and to allow me to establish the QNH of an airport or the cruise flight level.