Which projection should be chosen to model transmission lines across the USA?

I am looking at different options for high voltage power lines in the US. These power lines cross several states. Since in the end the distance is of importance, is the USA Contiguous Equidistant Conic Projection the right projection? If not, which one would you suggest?

• Do the distances you're interested in all originate from one specific point? – nmpeterson Mar 18 '15 at 21:29
• Is there something wrong with the suggestions (and explanation of why equidistant was not a good choice) you received in your previous question: gis.stackexchange.com/questions/136063/… ? – Chris W Mar 19 '15 at 5:06
• No there was nothing wrong with that explanation. However, I still don't know which projection would be the best choice and especially why. Also I did a lot of my processing with the Equidistant projection. Can I just change the projection in the end or do I have to process all again? – Stefanie Mar 19 '15 at 17:52
• Best is relative and it's hard to answer why in a couple of paragraphs (which may be why @AndreJ only gave suggestions and not rationales). Some resources: geo.hunter.cuny.edu/~jochen/gtech201/lectures/lec6concepts/… and wiki.gis.com/wiki/index.php/Map_projection and ryaninstitute.ie/wp-content/uploads/… Projection can affect processing results, so you might need to do it all again (use a different one and compare results, see if/how much difference it makes). – Chris W Mar 19 '15 at 21:17
• Quick experiment (rather than doing all the processing you've done already over again). Take your transmission line file and add two new double fields to it, say ProjA and ProjB. With your dataframe set to the current equidistant projection, Calculate Geometry on ProjA and get the length of the lines. Then change your dataframe projection to an equal area (this just reprojects on the fly, not changing data, and can be set right back) and do the same length calc for the ProjB field. Compare the lengths. – Chris W Mar 19 '15 at 21:28