to trace a line: to mark out where an edge runs, whether a boundary across the land or an outline on a block of wood
Both uses of this rare verb picture the same act, a line being traced from one point to the next. In Isaiah the line is a real one, scratched onto wood with a marker and a compass. In Joshua the line is one nobody can see, the edge of a tribe's territory, and the surveyor's words trace it the way the craftsman's tool traces a figure: from this hilltop over to that spring, then bending toward that town.
That is why one Hebrew word does the work of several English ones. English wants a verb of motion for a border (it "runs," "turns," "extends") and a verb of drawing for a carver (he "marks out," "outlines"). Hebrew uses its tracing word for both, so a border in Joshua reads less like a finished line on a map and more like a line being drawn as you follow it.
The same root gives Hebrew its noun for a shape or appearance (תֹּאַר), the outline a thing presents to the eye. The verb is the drawing of that outline; the noun is the outline itself.
It is a rare word, eight times in the whole Bible, and nearly all of those inside the land lists of Joshua. That is a narrow base to judge from, and it is why translations differ over whether a border "turns" at a place or is "drawn" onward to it.