units are 
s declevity 
bjective to 
1d operator 
t approach 
endent on 
y that the 
y rigid re- 
imizes the 
lacing the 
ons in the 
ied dimen- 
ale at the 
lecks to be 
, they are 
assible and 
plete edge 
fe, fast and 
hips, this is 
cause most 
vist or rack 
re they are 
ng the unit; 
at all key 
:tural fitting 
se of a 
ceuracy 
eo - mm 
rammetry T -) Imm 
per 
  
Table 1 
scissors lift or condo lift and really has few hindrances 
provided the targets are clean and in good shape. Target 
placement is depicted on an AUTOCAD sketch (Figure 2) 
which is directly tied into the Engineering AUTOKON 
database for accuracy. Customized LISP routines enable 
the Surveyor to extract design XYZ dimensions for each 
targeted point automatically. Next, images (typically 15 to 
40) are taken of the targeted unit at many converging 
angles from the same lift used in the targeting. Camera 
settings are usually quite constant at ISO 100, aperture 
setting of F16, and a shutter speed of 250. Image 
measuring is initiated by downloading the images into the 
PC or laptop, entering the control point data, and 
importing the design data for the target locations. Each 
image is then brought up on the computer screen, 
measured, and saved. This can be automated to a 
significant degree using the design data previously 
obtained or remain manual by measuring each point, one 
at a time, if needed. After many or all of the images are 
measured the data is merged together and XYZ 
coordinates are calculated through a least squares, self- 
calibrating bundle adjustment. Measurement is 
completed when all targets are within imaging and 
dimensional requirements and the resulting XYZ 
dimensions in object space have been transformed to the 
units local coordinate system. Quality control features 
enable the operator to view estimated accuracies for 
each target point measured and to edit images to obtain 
extremely consistent accuracy levels. The data for this 
edge is stored until the measurement process is 
completed for the interfacing edge of the mating unit. 
    
    
X Assembly Screen 
Select one or more hull Select one or mote units: 
Unit 
Once the stock edge and neat edge conditions are 
obtained, a comparision program is then run to calculate 
the amount of excess steel. The output to the structural 
trades is in the form of the original AUTOCAD sketch 
being modified to provide the target identification number 
and the amount of excess steel to be cut at each targeted 
point measured. Currently digital photogrammetry has 
neat cut over 150 structural units and the results clearly 
show it superior for this application (Table1). The data 
from the digital photogrammetry neat cut process is three 
dimensional, and is readily imported for use into BIW's 
Data Management System (SAS) for Statistical Analysis 
so that process control and process capability information 
is available for each stage of the construction contributing 
to the neat cut process. This provides our High 
Performance Work Teams (HPWT) feedback on the 
quality of their work. Figures 3 and 4 are representative 
of the versatility and functionality of software involved as 
they depict a menuing system and example of SPC 
outputs respectively. Also Structural Design and 
Accuracy Control personnel will have current information 
available pertaining to the amount of excess steel (stock) 
being cut, misalignment of structural members for height 
and halfbreadth, and structural alignment data at key 
shapes intersections (bulkheads, decks, shell plating). By 
analyzing this data in conjunction with the process 
control/capability information and by applying sound 
shipbuilding methodology, BIW plans to achieve a level 
of robustness that will shorten the transition time to neat 
construction and make it easier for the structural trades 
to maintain higher levels of fitup quality. 
  
  
Figure 3. 
267 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B5. Vienna 1996