Different distance in different projections

Discussion created by jlaroussi on Jul 7, 2011
Latest reply on Jul 8, 2011 by jlaroussi
On the daily basic I am using NAD_1983_StatePlane_New_York_Long_Island_FIPS_3104_Feet projection, but in order to overlay my network dataset with other data in the web application I had to reproject it to WGS_1984_Web_Mercator_Auxiliary_Sphere. After reprojecting my base feature class and building network dataset in a new projection my distance measurement changed. The distance which in  NAD_1983 is 4200 feet, in WGS_1984 is 1700 feet. I know the real distance is 4200 feet, but I do not know how to make my network dataset in WGS_1984 returns true distance. Any advice?