# How to determine a fuzzy tolerance

## Based on automation scale and digitizer precision

The most accurate method for setting the fuzzy tolerance is based on its automation scale and the digitizer precision. This table lists standard automation scales and the corresponding fuzzy tolerance for an industry-standard digitizer precision of 0.002".

Note:

The fuzzy tolerance always uses the unit of measure of the geodataset.

Automation scale of source data

Coverage coordinate units

Fuzzy tolerance (on the ground) at 0.002" digitizer precision

1:200 000

feet

33.333

meters

10.130

1:100 000

feet

16.620

meters

5.080

1:63 360

feet

10.560

meters

3.210

1:25 000

feet

4.167 (4.000)

meters

1.270 (1.219)

1:10 000

feet

1.668

meters

0.508

1:5 000

feet

0.833

meters

0.254

1:1 000

feet

0.167

meters

0.051

1:500

feet

0.083

meters

0.025

Automation scale table

If you don't see the automation scale of your geodataset in the table, calculate the fuzzy tolerance with this equation:

Tolerance in feet = ((automation scale * digitizer precision) / 12)

Tolerance in meters = ((automation scale * digitizer precision) / 12) * 0.3048

## Based on geodataset extent

If you don't know the automation scale of the coverage, an alternate method for setting the fuzzy tolerance is based on the coverage extent and uses the coordinate values stored in its BND. This table shows threshold values for various coverage extents:

Extent

Type of data content

Fuzzy tolerance (resolution)

Divide extent by

10

buildings/streets

0.001 m

10 000

100

census block

0.01 m

10 000

1 000

census block/tract

0.1 m

10 000

>1 000

city tract/town

0.1 | 0.9 m

10 000

10 000

city

1 m

10 000

>10 000

city/county

1 m

extent

100 000

county

1 m

100 000

1 000 000

state/small country

5 m

200 000

>1 000 000

continent to globe

10 m

1 000 000

Extent table

If you don't see the extent of your geodataset in the table, here's how to calculate the fuzzy tolerance:

• Determine the extent, that is, the larger of (xmax – xmin) and (ymax – ymin).
• Determine a sensible resolution for the type of data content, for example, census block, city, county, state, country, continent, or globe.
• Determine the denominator to get the desired resolution. Use the resolution as the fuzzy tolerance value.

The fuzzy tolerance for double-precision geodatasets is often smaller than that for single-precision coverages, since they are frequently collected from precise sources such as surveying, engineering, and Global Positioning Systems (GPS).

Published 6/8/2010