This COGO tool allows you to compute the offset of one point at a time, displaying the offset distance and bearing/azimuth right in the dialog box. You can also save the point on the line from which the offset distance is computed.
If you access this routine from the Traverse View or Point Manager, the highlighted point becomes the offset point, saving you keystrokes.
If you access this routine from the Drawing View, TPC evaluates the drawing object you selected. If that object references a survey point, that survey point becomes the offset point.
TPC does not automatically pre-set the line used in this dialog when you access it from a view because it uses the selected data to pre-set the offset point.
If you are not using geodetic distance and direction types and you recall an existing survey line, TPC will compute the offset to that existing line, regardless of whether it is a tangent, curve or spiral.
Use the From and To fields in the 'Line to Compute Offset To' box to specify the endpoints of the existing line or select it in the current drawing using the Line >> button. Once computed, the Offset and 'Distance from start of line' information displayed in the dialog will reference the arc of the referenced curve or spiral.
The Summary also clearly indicates that the offset is to a survey line and provides information about that line in the report view.
If you recall just the From point and not the To point in the 'Line to Compute Offset To' box, TPC projects an azimuth through the From point and creates the offset to that azimuth.
This also happens automatically if you use geodetic distance and direction types. Intersections of geodesics are not well defined and probably not what you are interested in when offsetting to a line.
When you open the Offset to Line dialog, you will have an option to compute offsets to a latitudinal arc.
If the arc you specify is East-West, TPC uses it's PLSS computations to compute the offset per the 2009 BLM Manual of Survey.
If you specify a North-South line, TPC does a bearing-bearing intersect, but applies convergence to the intersecting bearing. This provides a reasonable approximation for an offset to a meridian.
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COGO Commands - reference