What is a Gauss sign?

Question

I am reading the paper

"A Method for Extraction of Bronchus Regions from 3D Chest X-ray CT Images by Analyzing Structural Features of the Bronchus" by Takayuki KITASAKA, Kensaku MORI, Jun-ichi HASEGAWA and Jun-ichiro TORIWAKI

and I run into a term I do not understand:

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In equation (2), when we say "[] expresses the Gauss sign", what does it mean?

Answer 1

From the context (a change of scale using discrete units), this should certainly mean floor as on page 5 of Gauss's Werke 2

per signum $[x]$ exprimemus integrum ipsa $x$ proxime minorem, ita ut $x-[x]$ semper fiat quantitas positiva intra limites $0$ et $1$ sita

i.e. the next lower integer.