The Terra Standard Deviation Scale (usually: TerraStandard, short: TerS, unit: TS) is a scale measuring the relative habitability of a given environment. It is mostly used as a shorthand to describe a planet's or area's climate, though it can be used commercially to estimate the costs of potential colonization or terraforming efforts.

The TerS scale is set at zero for a perfectly habitable climate and enviroment, with the range from -1 to +1 denoting still habitable negative and positive deviations. TerS ratings below -1 and above +1 denote climates that are not habitable without appropriate shelter.

There is a long-ranging discussion about the scientific accruracy of this measurement, especially as the value of 'survivability' and therefor 'hospitability' is an arbitrary value and can differ wildly depending on the amount of hardship potential colonists are willing to suffer. None the less, the TerS rating is popular all over the Empire as a shorthand description and is used everywhere from tourism ads to local warnings.

The TerS catalog lists several hundred factors with their -1 to +1 ranges as denominators for survivability, from gravity and temperature to breathability of the atmosphere and background radiation. Usually, only a combined TerS rating is given for any given area, TerS ratings describing a specific factor are always given together with that factor.

Some example TerS ratingsEdit

Earth, mediterranean regions overall 0 TS
Del'Morad, overall temperature -1.2 TS
Kismet, overall temperature +0.6 TS
Leichnam, airborne spore density +0.9 TS

Famously, Shiraz is the only planet other than Earth that reaches a clear 0 TS all over, even exceeding Earth in so far as neither the polar nor equatorial regions exceed +1 / -1 TS.