Figure 1 
the trimming of this steel prior to erection so that the unit 
could be mated together neat in one short lift of the 
cranes. However; the traditional ‘neat cutting’ process 
was atheodolite based labor intensive process for the 
Surveyors. DCRP techniques into manufacturing is very 
cost effective benefits. A description of this transition 
follows: The traditional approach of neat cutting unit 
erections utilizes two Surveyors with a theodolite to 
measure the stock edge of a unit after it is assembled. 
The theodolite is set up in the production area, 
referenced into the local coordinate system, and each 
point is measured for length, width, or height manually 
from visual readings to a rule or rod placed at the 
required spots one point at a time until a complete girth 
or seam condition has been measured. This is an 
expensive, time consuming, and stressful process due to 
obstructions (staging, welding leads, sucker tubes, etc..), 
people working around the instrument, job site noise 
levels, and pressure to get the job done right , quickly (it 
is not uncommon for assembly units to be shipped to the 
next construction stage immediately after Surveyor read- 
ings are completed). The matching data to derive the 
neat cuts is obtained by repeating this process for the 
interfacing edge by taking readings of the actual 
condition of the ship on the erection ways. The output 
(neat cut data) from these two measurements is manually 
computed for each point and noted on a table provided to 
the structural team. Accompanying this list is a hand 
sketch depicting the location of each point. The results 
for this process as a whole are fully dependent on a 
266 
stable working platforms. preferably the units are 
positioned gravity level in assembly or on ships declevity 
out on the ways. This process is very subjective to 
surrounding working conditions, schedule, and operator 
skills but is cost effective, none the less. 
DCRP techniques employ a much different approach 
because the measurements are not dependent on 
special positioning or stable platforms, only that the 
object being measured remains structurally rigid re- 
gardless of its position. The first step minimizes the 
impact to production schedules by replacing the 
measurement of the complete edge conditions in the 
assembly areas by establishing predetermined dimen- 
sional references or control points for scale at the 
extremes of selected girths, seams, and/or decks to be 
measured. After the units are shipped out, they are 
tracked so that when they are the most accessible and 
the surrounding work is at a minimum the complete edge 
conditions can then be obtained in a very safe, fast and 
accurate manner. For the DDG 51 class of ships, this is 
very often done in storage areas (Figure 1) because most 
of the units are structurally rigid. Units that twist or rack 
are typically measured in Pre-outfit areas where they are 
leveled as part of their normal work cycle. 
The measurement process starts off by targeting the unit; 
placing magnetic retro-reflective targets at all key 
structural locations as requested by the structural fitting 
team. This task if usually performed with the use of a 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996 
  
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