OCC Forums » Seamanship » Navigation » Chartplotter anomaliesInstantForum 2017-1 FinalOCC Forumshttps://forum.oceancruisingclub.org/OCC ForumsMon, 20 Apr 2026 15:56:26 GMT20Chartplotter anomalieshttps://forum.oceancruisingclub.org/FindPost5253.aspxWe've had strange patterns show up on our chartplotter from time to time. Today was extreme. I noticed that each time the wacky zig zag patterns happened, the DGPS was off and we had GPS only. Can anyone offer an explanation so we can understand what's going on?&nbsp;<img src="../Uploads/Images/4cf868a8-c41a-48dd-95ce-85d2.jpg" data-download-url="../Uploads/Images/2dc4ebd1-96d2-4e62-89ce-398b.jpg" id="if_insertedNode_1561912849285"><img src="../Uploads/Images/1970c97f-7e10-48b3-88b8-204f.jpg" data-download-url="../Uploads/Images/08bfeff6-018c-41b7-b1ee-d9eb.jpg" id="if_insertedNode_1561912892056">Sun, 30 Jun 2019 16:42:23 GMTDariaBlackwell