Data in Meters, but you want Measured Values in Feet

GTViewer has had the ability to display measured result in units different from that of the data since version 8.   This feature is often useful if your data is in Meters but you want to display measured values in Feet; or if your data is in Feet and you want to display measured values in Meters.

Three entries support this feature in the [Additional Properties] section of the .GTM file:

·         MeasureFactor is a value used to divide the measured length (in system units) by to produce the measured value in the desired units.  By default, this value is set to the Coordinate Factor 2 value (which is used to divide the system coordinates values by to get real world units for the data).   So, if this entry is not used, the measured values will appear in the same units as the data.

·         MeasurePrecision can be used to specify the number of digits that appear after the decimal point in the measurement readouts.   If not specified, the default value is 2.

·         MeasureUnitLabel defines the unit label displayed in the measurement readout.  Since this unit is different than the data’s real world units (specified with MajorUnit), it must be specified if using the MeasureFactor entry.

Here are some typical examples of how these entries can be used:

Data in Meters, Measurements in Feet

If your data is in Meters, and you are using 1000 for Coordinate Factor 2 (meaning that you will divide the system coordinate by 1000 to get the real world units of the data), and you want to display your measurements in Feet, the settings would be:

MeasureFactor=3280.84

MeasurePrecsion=2

MeasureUnitLabel=FT

1 Meter = 3.28084 feet, so to determine the Measure Factor value, you need to divide the measured value in system units by 1000 (coordinate factor 2) to get Meters, then multiply by 3.28084 to get Feet.  The Measure Factor is 1000 *3.28084 = 3280.84.  Then the measured value in System Units is divided by the Measure Factor to get Feet.

Data in Feet, Measurements in Meters

If your data is in feet and you are using 1000 for Coordinate Factor 2 (meaning that you have 1000 system units per Foot), and you want to display your measurements in Meters, the settings would be:

MeasureFactor=304.8

MeasurePrecsion=2

MeasureUnitLabel=M

1 Foot = 0.3048 Meters, so to determine the Measure Factor, you need to divide the measured value in system units by 1000 (Coordinate factor 2) to get Feet, then multiply it by 0.3048 to be Meters.  The Measure Factor is 1000 * 0.3048 = 304.8.   Then the measured value in System Units is divided by the Measure Factor to get Meters.