From The RadioReference Wiki
GOTHAM - Geo-diverse Over The Horizon ALE Matrix
GOTHAM was designed by the USCG to advance HF-ALE communications to work similar to a cellular phone system. The main idea was to have the terrestrial system route an ALE call to the requested ALE address or telephone number. Point to point ALE calls could still be made, with the terrestrial network only taking over if point to point communications were not possible. This would improve communications by not only selecting the best frequency (Traditional ALE), but also selecting the best signal received geographically out of the entire radio pool. The mobile user would not need to know what ALE radios were within range, allowing them to reach the ALE address or phone number of the unit they are trying to contact without manual intervention.
The USCG partnered with CBP (then US Customs) to update the COTHEN software to implement the GOTHAM concept in the early 2000's, and the first instance of HF Cellular was created. Soon after, the USCG would implement the first GOTHAM site in Alaska and vastly improve on the reliability of their communications in this region. In 2017, the USCG GOTHAM site would be merged into the COTHEN system to create a DHS shareable network. While this sole instance of the GOTHAM concept creates a reliable long haul system, it still falls short of the entire GOTHAM concept that was, among other things, to fully integrate the system with the phone network to operate as a truly cellular system.