About distance units and editing
When editing, the map units of your data frame are used when reporting and entering measurements and distances. The map units are the units in which the spatial data in the data frame is drawn. The map units are determined by the coordinate system of the data frame. When editing, all the values you enter will be in map units by default. You can find out the map units used by your coordinate system on the Data Frame Properties dialog box > General tab.
Sometimes when creating features, you need to enter values that were recorded in different distance units than the coordinate system of your data. When you input measurements, in many cases it is possible to enter values in units other than map units by specifying a units abbreviation with the value.
For example, suppose your data is in a State Plane coordinate system and the linear units are U.S. survey feet. You are given measurements in meters. Rather than convert all the measurements to U.S. survey feet, you can type the abbreviation for meters, m, after the measurements, and the tools will convert the distance correctly.
Whenever you are typing a distance into one of the editing tools, you have the option to specify the linear units or simply type a number, which the tool will interpret as being in map units. Unit abbreviations only work when your data frame uses a projected coordinate system rather than a geographic coordinate system.
The following sections outline all the unit abbreviations supported when editing and describe how to implement them.
Metric units
Distance units |
Abbreviation |
Meters per unit |
Description |
---|---|---|---|
Kilometer |
km |
1,000 |
1,000 meters exactly |
Meter |
m |
1 |
International meter |
Centimeter |
cm |
.01 |
1/100 meters exactly |
Millimeter |
mm |
0.001 |
1/1000 meters exactly |
Imperial or international units
Distance units |
Abbreviation |
Meters per unit |
Description |
---|---|---|---|
Foot |
ft |
0.3048 |
Standard foot used in the United States. Also known as international foot or imperial foot that was used in most non-U.S. countries before the metric system. |
Mile |
mi |
1,609.344 |
Also referred to as a statute mile, equal to 5,280 international feet. |
Nautical mile |
nm |
1,852 |
The nautical mile is a unit of distance used primarily in sea travel and aviation. The nautical mile is defined as the average distance on the earth's surface represented by one minute of latitude. In 1929, the nautical mile was defined as exactly 1,852 meters, or 6,076.11549 feet, a distance known as the international nautical mile. |
Chain |
ch |
20.1168 |
66 international feet. |
Yard |
yd |
0.9144 |
3 international feet. |
Rod |
rd |
5.0292 |
1/4 chain, or 16.5 international feet. |
Link |
lk |
0.201168 |
1/100 international chain, or 66/100 international feet. |
Inch |
in |
0.0254 |
1/12 international feet. |
U.S. survey units
Distance units |
Abbreviation |
Meters per unit |
Description |
---|---|---|---|
Survey foot |
ftUS |
0.3048006096 |
The U.S. survey foot is used in the state plane coordinate systems. In the United States, fundamental survey units, such as rods, chains, statute miles, acres, sections, and townships, all depend on the U.S. survey foot. An exact conversion to meters can be accomplished by multiplying U.S. survey feet by the fraction 1,200/3,937. |
Survey mile |
miUS |
1,609.3472186944 |
5,280 survey feet. |
Survey chain |
chUS |
20.1168402337 |
66 survey feet. |
Survey rod |
rdUS |
5.0292100584 |
1/4 survey chain. |
Survey link |
lkUS |
0.2011684023 |
1/100 survey chain. |
Survey yard |
ydUS |
0.9144018288 |
3 survey feet. |
Entering specific locations (DD, DMS, DDM, MGRS, USNG, and UTM)
In commands that require you to enter a specific location when editing, you can specify the location as a longitude-latitude coordinate pair, a Military Grid Reference System (MGRS) grid location, a U.S. National Grid (USNG) location, or a Universal Transverse Mercator (UTM) coordinate. Map units are the default, but you can click the Units button to choose the units in which to enter coordinates.
These are the same formats used by the Go To XY command. Below are some guidelines for specifying these values. These apply to Absolute XY and commands such as Move To that allows you to move a vertex or topology element to an exact location.
- Remember that x is longitude (East/West), and y is latitude (North/South)—the same order in which coordinates are listed in the status bar. Spherical coordinates aren't always specified in this order, so make sure you enter longitude first in this dialog box. For example, if someone asks you to plot 17.1325, -60.666 on the map, ask them if these coordinates are in longitude-latitude or latitude-longitude order. The only way to tell the order from the coordinates themselves is if they contain E, W, N, S characters to signify the hemisphere.
- When you are using decimal degrees (DD), degrees minutes seconds (DMS), or degrees decimal minutes (DM), coordinates can be entered by using a minus sign before the numeric value to signify the western or southern quadrants or using E, W, N, S characters before or after the numeric values.
- Values in DMS and DM coordinates can be separated with spaces or the °, ', " special characters (such as when you paste coordinates that you have copied from other dialog boxes or applications that use those characters) or both.
- Regardless of whether you are using DD, DMS, or DM in the dialog box, coordinates can be entered in any of these three longitude-latitude formats and are automatically converted to match your chosen format.
- When you are using DD and DM, coordinates you input are always converted to use a minus sign to signify W or S.
- When you are using DMS, coordinates you input are always converted to use E, W, N, S to signify quadrants and are given the °, ', ", special characters.
- When using MGRS, USNG, or UTM locations, make sure there are no spaces in the coordinate string.
-45 |
-45 |
45 W |
45 S |
45.50W |
45.50S |
W45 |
S45 |
45 30.5W |
44 30.5S |
45° 30'30"W |
45°30'30"N |
45 30 30 W |
45 30 30 N |
-45 30 30 |
45 30 30 |
45 30.50W |
45 30.50 |
-45.50833 |
45.50833 |
18SUH |
100,000-meter square |
0-digit coordinate |
18SUH64 |
10,000-meter square |
2-digit coordinate |
18SUH6743 |
1,000-meter square |
4-digit coordinate |
18SUH678432 |
100-meter square |
6-digit coordinate |
18SUH67894321 |
10-meter square |
8-digit coordinate |
18SUH6789043210 |
1-meter square |
10-digit coordinate |
Conversion constants
You can use conversion constants to convert from one measurement system to another. The measurement system to be converted should be multiplied by the associated conversion constant. For example, to convert feet to centimeters, multiply feet by the conversion constant of 30.48 (27 feet x 30.48 = 822.96 centimeters). For a list, refer to the PDF of conversion constants.
If this link does not work, you can open the conversion_constants.pdf from the \Documentation folder in the directory where you installed ArcGIS. To view this document, you need a copy of Adobe Reader.
About the U.S. survey foot
In 1959, the directors of the National Bureau of Standards and the United States Coast and Geodetic Survey agreed on a redefinition of the inch-centimeter relationship. This redefinition defined 1 inch as equal to 2.54 centimeters exactly, or 1 foot as equal to 0.3048 meters exactly. However, their agreement stipulated that the older value for 1 meter equaling 39.37 inches exactly be retained for identifying the U.S. survey foot.
One of the reasons for this retention was that the state plane coordinate systems, which are derived from the national geodetic control network, are based on the relationship of 1 meter equaling 39.37 inches exactly.
The difference between these two values for the foot is very small, two parts per million, which is hardly measurable, but not trivial when computational consistency is desired. Fundamental survey units, such as rods, chains, statute miles, acres, sections, and townships, all depend on the relationship of 1 meter equaling 39.37 inches exactly.
The U.S. survey foot table represents the corrected values (or U.S. survey values), using the 39.37-inch conversion value.