Found out something new the other day regarding the waypoints shown on these approach plates for LOWI. Take a look at 19-10, the Special Circling Procedure.
This is a transition from an instrument approach to a visual approach at DME 6.3 (OEV) into LOWI.
This uses a VOR/DME. A VOR/DME is a radio beacon that combines a VHF omnidirectional range (VOR) with a distance measuring equipment (DME). The VOR allows the receiver to measure its bearing to or from the beacon, while the DME provides the slant distance between the receiver and the station.
Each point has a measurement from both the DME and the VOR. So let’s zero in on D4.2 OEV/D6.5 OEJ. So if you’re flying that approach and you’re 4.2nm from OEV, the DME, and 6.5nm from OEJ, the VOR, on a heading of 255, you’d know you are on course. Each point is a measurement to aid the pilot while they use their radio equipment to measure the distance they are from both the VOR and DME.
Mind blown, and very good to know. Hope that helps you when you attempt to land at LOWI.
1. “How It Works: Distance Measuring Equipment” by AOPA, December 1, 2017.