Page 79 control and signal building 2261 



be found in pages 38 to 41, Special Publication No. 145, Manual of Second- and Tliird- 

 Order Triangulation and Traverse. 



2261. Resetting Station Marks 



Whether an old station is to be re-marked or not, often depends on the judgment 

 of the person recovering the station. Under the following conditions, however, a station 

 should always be re-marked: 



(a) The old station is marked by a chiseled cross, a drill hole in rock, or some other method not 

 using a standard bronze disk. In such instances the station should be re-marked by a standard disk, 

 if this is practicable, so that the station will be better perpetuated and more easily identified and 

 recovered. 



(6) The disk in the recovered station mark is loose, the concrete block is cracked or is in poor 

 condition. 



(c) The station mark is destroyed but the subsurface mark is recovered without a question of 

 doubt. 



(d) The station mark is destroyed but two or more reference marks are recovered. A new 

 station-mark disk can be established in the geographic position of the original station if: 



(1) Two reference marks are recovered and sufficient evidence of the original station mark is found to assure the re-marking of the 

 station without a doubt by the intersection of distance arcs swung from the reference marks, using the horizontal distances given in 

 the description of station. 



(2) Three reference marks are recovered and the three distance arcs intersect at a point, using the horizontal distances given in the 

 description of station. 



If the station mark is missing but the requirements in (c) or (d) are not met, and 

 a station is needed in this locality, a new monument should be set and given the same 

 name as the original station with the number 2 added as a suffix. (See paragraph 4 of 

 2156.) This station must then be located by triangulation or traverse from adjacent 

 stations. If the station mark is missing but none of the requirements in (c) or (d) is 

 met and the station is not needed in this locality, then the marks should be left as 

 found. (See 2272 relative to recovery reports.) 



To ensure that the station is re-marked precisely in the original geographic position, construct a 

 bench about 1 foot high over the station. The bench is constructed from a piece of 1- by 4-inch soft 

 lumber supported by 2- by 4-inch stakes driven in the ground far enough away from the station so as 

 not to be disturbed by the removal or resetting of the station mark. One end of the bench is nailed 

 to the top of a stake by a single nail and the other end is swung into position on the other stake so that 

 an edge of the bench is directly over the center of the old station-mark disk. In this position the 

 free end is lightly nailed to its corresponding stake so that the nail penetrates the stake not more than 

 one-fourth inch. With a plumb bob suspended directly over the station mark and the string running 

 over the edge of the bench and across the top, the position of the string is marked by a small notch 

 cut in the edge of the bench. The lightly nailed end of the bench is then pried off its stake, swung 

 around out of the way and temporarily supported. The old mark is then removed, reinforced and 

 reset, or replaced by a new mark and the disk set in the exact location of the original position by swing- 

 ing the bench back into position, fitting the nail into its former impression and plumbing down from 

 the notch in the edge of the bench. See illustration on page 5, Serial 632, The Preservation of Trian- 

 gulation Station Marks. 



The stamping of station and reference marks at control stations of other organiza- 

 tions is discussed in 224. 



2262. Relocating Station Marks 



When instructions are issued to a party to preserve, or move and relocate, a 

 station endangered by a new highway, or other construction, one of the following methods 

 shall be used: 



(a) If the original horizontal position can be retained, but at a different elevation, and the bench 

 method described in 2261 is impracticable, set two stakes preferably less than 30 meters and never 



