In LDT, as part of drawing setup, a set of text styles is created based on information contained in a file with a .STP file extension, most commonly used is the LEROY.STP. These text styles all have fixed heights assigned to them, based on the current horizontal scale set in the drawing. If the horizontal scale is changed, the heights of the text styles are all changed.
In Carlson Civil, each of the various commands that involve annotation set the text style to be used and the desired height for the text, using a "scaler", which is multiplied by the current drawing scale. The AutoCAD text style should be set with a height of zero.