A GPSImgDirection of 271.5 means the camera was facing a touch north of due west when the shutter fired. The tag (0x0011) is a compass bearing in degrees, clockwise from north, from 0 to 359.99, so 90 is east and 180 south. Its partner GPSImgDirectionRef (0x0010) says which north, T for true (geographic) north or M for magnetic north.
[GPS] GPSImgDirectionRef : True North
[GPS] GPSImgDirection : 271.5The bearing is a single unsigned rational, 543/2 in this file. ExifTool prints it without a unit and spells out the Ref letter unless you pass -n.
True north or magnetic north
The difference between the two is the magnetic declination. It depends on where you stand and drifts year to year: close to zero across parts of Western Europe at the moment, around 15 degrees in the Pacific Northwest. A heading saved as M and read as T is off by that much, and nothing warns you. Phones measure the field magnetically and correct it with a declination model; iPhones write T. A dedicated camera with a built-in compass may write either, so check the Ref before plotting anything.
Easily confused tags
GPSTrack (0x000F) is the direction of travel. It only matches the camera direction if you shoot straight ahead out of a moving car. GPSDestBearing (0x0018) is the bearing toward a subject, which some phones fill as well. Neither has anything to do with Orientation, which tells a viewer how to rotate the pixels.
How much to trust it
Phone magnetometers get pulled off by steel railings and parked cars, and can be wrong by tens of degrees without any warning in the file. Use the value as a hint.
It is still revealing. Together with the GPS coordinates, a heading narrows down which window or balcony a picture was taken from. The EXIF editor shows both tags and can change or clear them on JPEG and TIFF; iPhone HEIC files carry them too, but need ExifTool or a conversion first. The guide to finding where a photo was taken puts the coordinates on a map; the heading tells you which way to look from that pin.