VERIFIED SOLUTION i
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Resolving discrepancies in Study Area's actual area vs. area used in internal calculations in AnySite

Issue

User creates a Ring Study in AnySite and reports out Total Pop and Pop Density, which is defined
as POP/LandArea (sq. mi.)
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User then runs a Demographic Report:

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For 1 mile Ring, user manually calculates Pop density by dividing 52,704 by the area listed in the header for the 1 mile ring, 3.14 sq. mi. and he gets 16,785 as the Density.
But the report lists the Pop Density as 25,381.

 

Cause

The reason the AnySite report lists POP Density at 25,381 is because within AnySite,
the LandArea function (the way the ASDE engine calculates Area) finds all the block centroids within the study area and aggregates the area of all of the associated Block Groups who's centroids are contained within the given study area. 
This means that there are potentially BG's who's centroid falls within the ring but have additional area OUTSIDE the ring.

Resolution

UPDATED: September 8, 2017


The area listed in the header of the report for the ring is the actual area of the ring and does not take into account those portions of BG's that fall outside the ring but contribute to the LandArea calculation.
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So, in this case, users would expect the results that reported: 
If users selected all the block centroids contained within a 1 mile ring and summed the area's of the associated BG's,  the result would be a number greater than the area of the 3 mile ring.

This Block Centroid Methodology has been vetted by Demographer's as statistically sound.

Environment Details

Products affected: AnySite™
 

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