TPC 2026 - Changing Units Using Coordinate Conversion

Navigation: Coordinate Reference Systems > Converting Coordinates >

Changing Units Using Coordinate Conversion

To Change Units in an Existing Survey

•From the desktop menu, choose Tools | Coordinate Conversion.

•From the Coordinate Conversion dialog, choose the units you want to convert to.

•If you want to convert so that all the points converge on a specific set of coordinates, recall the point with the coordinates in Base or enter them as Y, X and Z.

•If you are converting English to metric or vice versa, choose the conversion factor you want.

•Choose OK.

When you choose OK, TPC recomputes the coordinates of the entire survey so that the points are at the same physical position, but the coordinates are expressed in the new units. For example, a coordinate of 100/100 chains would be converted to 6600/6600 feet.

Note: The units you select here only affect the current survey. New traverses will use the default units you set in the Tools | Program Settings | Units dialog box.

Note: ** The units of the survey only change when the entire survey is converted. If you convert parts of the survey (a single traverse or point) you must remember the units they were converted to in order to convert them back if you need to.

Changing Units without Changing Coordinate Values

Sometimes data comes in with the right numbers but the wrong units. For example, assume that you import an ASCII Y, X, Z file and that the current survey units are feet, but the coordinates in the file are in meters. You do not want to convert from feet to meters since that would change the coordinate values, but you want your areas to be displayed in hectares.

The solution is to change Feet to Meters, but enter your own factor of 1.0. This will convert the survey units without modifying any survey data.

Scaling Coordinates

You can also use the Coordinate Conversion to scale coordinates without changing the units.

Let's say that you are given and ASCII coordinate file in which the coordinates are Ground coordinates. Since TPC assumes all coordinates are Grid, you will need to convert the imported coordinates from Ground to Grid. TPC can do this.

TPC also allows you to specify a base point for the conversion or use 0,0. All factoring is computed from this base point.

Grid <=> Ground

The From and To pull downs in the Coordinate Conversion dialog include Ground and Grid selections. TPC treats these in a unique way as follows.

If you select Grid for either From or To, TPC will specify Ground for the other. If you select Ground, TPC will specify Grid for the other.

Grid <=> Ground conversions do not modify elevations. They are strictly X & Y conversions.

Grid <=> Ground conversions do not not change coordinate units. If the survey units are meters before the conversion, they are meters after the conversion.

Conversions Rules

Depending on the options you selected for a conversion, TPC converts points, lines and raw data using the following rules.

Points

Survey points are converted by converting their distance from a base point. Often times, you will use a base point of zero, so the coordinates will simply be converted from Feet to Meters, or Feet to Chains. If however, you select a base point, either by selecting an existing point or entering base coordinates, TPC inverses the distance from each point to the base, then converts the distance and recomputes the point.

Protected points are converted ONLY if the option to converted protected points is selected.

Lines

Lines are converted only if both end points of a line are also converted. So if a line has end points 10 and 11, it will only be converted if both points 10 and 11 are converted. If one of the points is not converted, TPC will display a warning message saying that the line was not converted because one or more end points were not converted.

When a line is converted, TPC converts just the data stored with the line. This includes radii and spiral lengths. So if you have stored the radius of a line in feet and convert to meters, TPC will convert the radii to meters.

Raw Data

Raw data is converted by converting each distance value stored with the raw data. If you entered a slope distance to a foresight, that distance will be converted. No conversion is required for bearings, azimuths and angles.

Vertical components are converted along with horizontal. So instrument height, target height, vertical elevation, etc. are all converted.

Editions

Personal, Premium, Professional