Plotting lines at 90 degrees to existing

Discussion created by 110240PUG on Jun 26, 2014
I have some straight lines that have been drawn based on geospatial data in an underlying map.  What I would like to do is plot a second set of lines orthogonal to the existing lines.  So if I start with an EW line like "-" it would become "T". 

As I understand GIS the direction of the second line can be either up or down and is based on the way that the original line is drawn.

Can anyone advise me on a good way to do this? 
Many thanks,