RSS
RSS turns up in 2 fields: geosynthetics, metrology. Here is what it means to the people in each one.
RSS in geosynthetics
Reinforced soil slope: an embankment built steeper than its fill could stand alone by layering geogrid or geotextile in it.
Short for reinforced soil slope, a face steeper than the fill could hold unaided but flatter than 70 degrees, the angle where design switches to wall methods. Primary reinforcement layers carry the main load, and shorter secondary layers near the face stop shallow sloughing during compaction and rain. The face is usually vegetated through erosion control matting or wrapped in geotextile.
"RSS on the east side goes in at one-to-one with grid every two feet and turf mat on the face."
RSS in metrology
Root sum of squares, combining independent uncertainty contributions by squaring, adding and taking the square root.
RSS stands for root sum of squares: square each independent standard uncertainty contribution (already multiplied by its sensitivity coefficient), add them, then take the square root. Contributions of 0.6, 0.8 and 0.3 combine to about 1.04, far less than their straight sum of 1.7, because independent errors rarely all push the same way at once. RSS is valid only for uncorrelated terms; fully correlated terms add linearly instead.
"Don't add them linearly, RSS the contributions and you're at 1.04 ppm, not 1.7."