I want to use ArcGIS 10.1 to calculate the straight (euclidean) distances from zip codes to their nearest city centers in about 300 U.S. metropolitan areas. I have two point shpfiles: one includes the centroids of all zip codes and the other includes the points that represent city centers. Both of the two shpfiles are in the GCS_North_American_1983, which prohibits me from doing the distance calculation.
I have converted the GCS into North America Lambert Conformal Conic to do the calculation. It worked. But I am not sure whether this is the best way to do it. Any advice is appreciated!