ERDAS IMAGINE 2018 Update 1 (v16.5.1), to be released in the June/July, 2018 timeframe, will address the following issue (IM-43870 / 00026039):
Customers have reported that when using ERDAS IMAGINE 2016, the Autosync product can take a very long time to run the Automated Point Matching (APM) process to find common control points between the two images being matched. The time taken has increased significantly over previous versions of the software. The problem was found to be related to the process of computing the active area of the input imagery (e.g. if the input images had significant areas of background data, calculating the locations of the true image edges was taking too long).
The solution was to use the same fast edge-detection algorithm as had been introduced into MosaicPro.
This change will be made available to all customers as part of ERDAS IMAGINE 2018 Update 1.