# Closest Site

The Closest Site stage identifies the closest sites to a given location. Examples include:

• Banking—Find the nearest branch to a retail store for night deposits.
• Insurance—Establish a list of doctors with offices closest to a patient.
• Retail—Use distance from a set of customers to a specific store location as a variable in a statistical model.
• Public Safety—Determine the number of homes within a three-mile radius of a fire station.

Closest Site is used with a Centrus database and is part of the Spatial Module. For more information on this module, including a listing of other components included with it, see Spatial Stages.

Keep in mind that there can be some variance in the calculations performed by Closest Site. These potential variances increase as the north-south distance between points increases. This is because as you go north or south from the equator, the circumference of each latitude decreases, introducing variance to the calculation. The following table shows the maximum variance for points oriented north or south of the base point, which have the largest potential variance.

North/South Distance

Maximum Variance

50 miles

0.25% (0.1 miles)

200 miles

0.9% (1.8 miles)

400 miles

1.25% (5 miles)

1000 miles

1.9% (19 miles)

Variance exists only in calculations of north-south distance, not east-west distance, because longitudes always have the same circumference. No matter where two points are on the Earth, when you calculate the east-west distance, the calculation will always be correct.