Mobile and Pervasive Construction Visualization Using Outdoor Augmented Reality - Mobile and Pervasive Computing in Construction - page 69

Figure 5.10 Sample scenarios involving positional measurement problems
points on the augmented scene becomes a time consuming and sometimes an
impossible task.
As a common practice in drawing the site layout plans, local position of
important objects is defined relative to the positions of a number of known
surveying benchmarks. Sometimes the only points on the site with known longi-
tude, latitude, and altitude values are benchmarks, and the positional values of
everything else is measured and calculated relative to these points. While obtaining
the global position values for every item on a construction site is a very time
consuming and often impossible process, finding these values for only a few points
and placing others relative to them seems to be a more reasonable approach.
As described in Table 5.1, the POSITION statement is used to place a static or a
moving object in the augmented scene by defining its global coordinates (e.g.
longitude, latitude, and altitude values). To improve the initial design of the
POSITION statement and make it more powerful and practical, it was further
modified to also accept local point coordinates relative to a reference point with
known global coordinates. Hence, a numerical algorithm was developed and