Regard the Jeppesen version of the RNAV (GPS) Rwy 19 approach to Meridian, MS (KMEI). This chart shows the simplest TAA you can have. The limit for a turn based on GPS is 90 degrees, so the maximum allowable turn from a route direct to the IAF to the leg after crossing the IAF is 90 degrees. This means each TAA should contain at least two sectors, divided by courses 90 degrees off the inbound course.
Terminal Arrival Areas (TAAs) simplify GPS-based approach entries by defining sectorized minimum altitudes to the IAF, effectively replacing traditional feeder routes and Minimum Safe Altitudes (MSAs) on RNAV charts.
Early attempts to integrate TAAs into non-RNAV (e.g., ILS) charts resulted in confusing "GPS Required" notes that often failed to clarify GPS was only necessary for the TAA segment, creating ambiguity for pilots.
The absence of MSAs on TAA-equipped charts, even for non-GPS approaches, highlights potential challenges for emergency navigation; however, modern charting is improving clarity, and the decommissioning of VORs signals increased reliance on GPS for future procedure entries.
We pilots trust our cartographers. We must. We may wend our way from waypoint to waypoint, following the magenta pixels, but it’s black course lines and data on the chart that actually keep us out of trouble.
And then some well-meaning ground-dweller tries to simplify the presentation and bollixes up the whole thing.
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