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ModelGeometry Significant Size


Is there any reason why the value "ModelGeometry Significant Size" change from the CDB specification 3.0 to 3.2 ? 

Table 3-17. GSModelGeometry LOD Significance Size in CDB 3.0

Table 3-1: CDB LOD vs. Model Resolution in CDB 3.2 




The table values have not changed. If you look closely, the table format has changed to make LOD transition more clear.

In CDB 3.0 document

          LOD -9 is defined as "27.829 km < LOD Significant Size ≤ 55.659 km"

In CDB 3.2 document

          LOD -9 is defined as "SS > 2.782975 × 10+4"

The value is the same (using ENG notation in spec 3.2). The range specified in 3.0 becomes implicit from the other LOD definitions in the CDB 3.2 table. 

More importantly, the definition of the significant size for 3D models has been clarified in section 6.8.3. Section points to using the diagonal of the box shape as opposed to the model height in CDB 3.0. Yet, this does not change the table of Sig-size to LOD equivalence, it only improves the way to estimate the sig size for a given model geometry - giving equal weight to wide objects and high ones.



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