Use this procedure to convert the X,Y coordinate values in an ASCII file to a different projection.
Select Tools | Coordinate Calculator from the ERDAS IMAGINE main menu.
Set the Input and Output projections under the Projection menu. The example below shows the options for Geographic Lat/Lon as Input, and UTM as the Output.
Now, you must import the data from the ASCII file.
The Options button allows you to specify the order that the column data is imported and the Separation Character and Row Terminator Character for your ASCII file. If your ASCII file contains column headings, you can specify the Number of Rows to Skip.
The final results should look similar to the dialog below.