Local X,Y to Long,Lat

Use the Coordinates > Georeferencing > Local X,Y -> Long,Lat menu option (XY2LL GX) to convert local X,Y coordinates to longitude and latitude coordinates using a defined reference location and orientation in a local coordinate system.

The GX uses two dialogs:

  • The first dialog allows you to select the input and output channels.

  • The second dialog defines the conversion parameters.

The script parameters are the same as for the LL2XY GX, allowing the inverse conversion to be performed using the same parameter values.

Local X,Y -> Long,Lat dialog options

Local X channel

The name of the input local X channel.

Script Parameter: LL2XY.X

Local Y channel

The name of the input local Y channel.

Script Parameter: LL2XY.Y

Longitude channel

The name of the output longitude channel.

Script Parameter: LL2XY.LON

Latitude channel

The name of the output latitude channel.

Script Parameter: LL2XY.LAT

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

Local X

The local X coordinate of the reference geographic location.

Script Parameter: LL2XY.LOCX

Local Y

The local Y coordinate of the reference geographic location.

Script Parameter: LL2XY.LOCY

Local length units

The units of the local coordinate system, selected from POSC-compatible abbreviations (for example, “m” or “ft”).

Script Parameter: LL2XY.UNITS

Local grid Y direction (deg azimuth)

The azimuth of the local Y-axis, measured clockwise from geographic North.

Script Parameter: LL2XY.AZM

Longitude of local (X,Y)

The longitude of the geographic reference location associated with the defined local (X,Y) origin.

Script Parameter: LL2XY.LOCLON

Latitude of local (X,Y)

The latitude of the geographic reference location associated with the defined local (X,Y) origin.

Script Parameter: LL2XY.LOCLAT

Application Notes

This procedure is useful if you have data points with known local X,Y coordinates defined using a reference location and orientation, and you want to convert them to longitude and latitude coordinates.

The local X,Y coordinates are first rotated according to the specified Y-axis azimuth, then converted to longitude and latitude using the inverse Transverse Mercator projection centered on the reference location.

A local coordinate system is an arbitrary Cartesian coordinate system defined and oriented for the purposes of a particular study.