If you have a handheld GPS, especially one with waypoint averaging, you can use it to get a good approximation of true north from a given reference point.
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You may want to use another method to evaluate how
good your Oregon, or any other single frequency handheld GPS device, like your phone, fitbit, etc., such as what I've laid out in the OP video, or what SLOweather mentioned (if you've
good aerial imagery). In this quick example shown above, I stood close to the previously calculated 17wx ref waypoint that was uploaded to the Oregon 550. For those unfamiliar with the display, the triangle represents the user's current position.
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Your Oregon can be configured to display a user grid which will provide northings and eastings to the nearest 1 foot, such as it can. If a more precise device was used, a side discussion about convergence angles might come up, but at the likely short distance between marks, it would still be a moot point. Regardless, you might find using a user grid more convenient than calculating the linear distance from geodetic positions.
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Also, once you've logged your waypoint (or averaged waypoint), your Oregon can project a new point along any bearing; e.g., 0° (true), and distance.