From https://edxwireless.atlassian.net/jira/servicedesk/projects/EDIT/queues/custom/6/EDIT-1152
The .GRC clutter files are from Planet → MapInfo → Vertical Mapper. EDX previously supported an integration with Vertical mapper that would allow SignalPro to convert .GRC files into EDX’s .GCV and .201 filesEDX SignalPro is a 64-bit only program. With our update to 64-bit only, we no longer support integration with Vertical Mapper in most recent versions of SignalPro. Vertical mapper is a tool in MapInfo. Prior to our update users could take files from vertical mapper and bring them into SignalPro.
Unfortunately, Pitney Bowes (which owns MapInfo) no longer supports Vertical Mapper and did not update it to run on 64-bit platforms. SignalPro is now 64-bit only and therefore we cannot support the integration with Vertical Mapper in the most recent versions of SignalPro.
Supporting link from Pitney Bowes: https://support.pitneybowes.com/SearchArticles/VFP05_KnowledgeWithSidebarHowTo?id=kA180000000Cm97CAC&popup=false;&lang=en_US