SQL Server / C＃如何找到一个与多边形相交的线串的DateTime

I am building a tracking system and want to find when someone has entered or left an area (Zone or Tier). We are collecting GPS coordinates at 5 sec intervals and they are stored as both lat/long and in a geography column along with the reading date time. The geofences for Zones and Tiers are stored as polygons in a geography column. Zones can contain Tiers and Tiers can contains Sub-Tiers. In the picture, T3 is a sub-tier. If someone is in T3, they are also in T2. The very faint set of dots on the right is also an example of what will happen. People will be going in and out of Zones and Tiers all day long.I am building a tracking system and want to fin