M2
metric involved little if any effort.
There has been significant
discussion among our partners at
Our regional electronic surveying and
NEMA and in the conduit
mapping equipment provides data in
manufacturing field regarding
metric. Many states also utilize
designations of various conduit
electronic data measurement (EDM)
types.
equipment which almost always can work
in metric units.
Most important is these products
will be physically identical. Look
Civil / Surveying
to NEMA for future guidance.
Two primary agencies producing survey
Wire Size Almost all cable firms
data are National Geodetic Survey (NGS)
contacted make metric sizes for
and US Geological Survey (USGS). SI
export, or can make them. Minimum
database information is available.
orders vary.
NGS horizontal and vertical control
Projects with medium and larger wire
point network has been SI since 1983.
requirements may wish to start using
Benchmark elevations are meters.
international sizes, where permitted
by governing codes and criteria.
UTM and State Plane Coordinates Systems
are metric.
Many projects have begun to refer to
existing sizes by mm2 dimensions, to
Almost 40 states have adopted metric in
become familiar with mm2 scale.
their state plane coordinate systems.
These are mm2 equivalents with
Project Data Most engineers are now
detailed rounding. In some cases,
using meters for survey elevations,
rounding to nearest 0.1, 1, or more
contour intervals, and large scale site
mm2 may be feasible. Use
drawings. Feel free to use m or mm.
professional judgement.
Convert benchmarks from feet to m or
AWG-mm2 22-0.506 20-0.517 18-0.82
mm.
16-1.31 14-2.08 12-3.31 10-5.26 9-
Ex, 314.15 feet becomes 95.753 m (95
6.6 8-8.37 7-10.6
753 mm)
6-13.30 5-16.8 4-21.15 3-26.66 2-
33.63 1-42.41 1/0-53.48 2/0-67.44
Smart Technique We have seen large
3/0-85.03 4/0-107.2
mapping scales use SI symbols. 1:2000
was written as 1:2k, 1:5,000,000 as
kcm-mm2 250-126.68 300-152.01 350-
1:5M.
177.35 400-202.68 450-228.0 500-
253.4 550-278.7 600-304.0 650-329.4
Electrical
700-354.7 750-380.0
800-405.4 900-456.0 1000-506.7
Conduit will not physically change by
1100-557.4 1200-608.1 1250-633.4
switching to metric. It becomes
1300-658.7 1400-709.4 1500-760.1
classified by a nominal mm size.
1600-810.7 1700-861.4 1800-912.1
1900-962.7 2000-1013.4
24
Previous Page
