Long,Lat to Local X,Y

Use the Coordinates > Georeferencing > Long,Lat -> Local X,Y menu option (LL2XY GX) to convert longitude/latitude coordinates to X,Y coordinates, based on a common known location and direction on a local coordinate system.

There are two dialogs for this GX. The first dialog enables you to select the input and output channels, and the second dialog is used to set the conversion parameters.

Long,Lat -> Local X,Y dialog options

Longitude channel

The name of the existing longitude channel.

Script Parameter: LL2XY.LON

Latitude channel

The name of the existing latitude channel.

Script Parameter: LL2XY.LAT

Local X channel

The name of the local coordinate X channel.

Script Parameter: LL2XY.X

Local Y channel

The name of the local coordinate Y channel.

Script Parameter: LL2XY.Y

Convert (Longitude, Latitude) to Local (X,Y) dialog options

Longitude of local (X,Y)

The longitude of the local (X,Y) coordinate.

Script Parameter: LL2XY.LOCLON

Latitude of local (X,Y)

The latitude of the local (X,Y) coordinate.

Script Parameter: LL2XY.LOCLAT

Local X

The local X coordinates.

Script Parameter: LL2XY.LOCX

Local Y

The local Y coordinates.

Script Parameter: LL2XY.LOCY

Local length units

The local length units selected from POSC compatible abbreviations. Normally "m" or "ft".

Script Parameter: LOOKUP1.UNITS

Local grid Y direction (deg azimuth)

The direction of the local grid Y axis in degrees azimuth (clockwise) from geographic North.

Script Parameter: LOOKUP1.AZM

Application Notes

This procedure is useful if you have data points with known longitude and latitude coordinates, and you would like to work on a map/local X, Y coordinates.

  • For the "Projected" method, the X, Y coordinates are calculated based on a projected map coordinate system by running NEWXY GX.

  • For the "Local" method, the X, Y coordinates are calculated by projecting longitude/latitude coordinates to a Transverse Mercator projection with a central meridian through the specified local (X, Y) and then rotating to the required Y azimuth by running LL2XY GX. A local coordinate system is an arbitrary Cartesian coordinate system that has been located and oriented for the purposes of a particular study.

See Also: