Geodetic survey markers are often set in groups. Reference Marks bear an arrow that point back to either a triangulation station or a benchmark. These Reference Marks (RMs) made it easier to find the primary mark. Reference Marks also make it possible to replace (or reset) a station mark that was disturbed or destroyed.
Reference Marks are usually within 30 meters (98.43 Ft) from the station, because that's the 'Tape length' carried by most surveyors, back in the day. Another guideline was to place RM #1 in the 1st 90 degree quadrant (clockwise from true north) and RM #2 in the next 90 degree quadrant etc. This 'direction' placement is just a guide though - Finding a good rock outcrop boulder in the area probably dictated 'where' on the compass the RMs were/could be placed.
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