See if you use high-tech instruments to measure or forget it yourself. If you use high-tech instruments, GPS will do, and sextant can be used to make something primitive. If I had to do it myself, I would have led my classmates from the Astronomical Association to do it in college. I set up a pole on the ground and kept drawing its shadow. When the shadow is the shortest, record the direction of the shadow at this time. This is due north. Measure the length of the shadow and pole at this time, calculate the elevation angle of the sun with trigonometric function, then consider the date number of measuring the distance between spring (autumn), summer (winter), calculate the latitude of the direct point of the sun on that day with trigonometric interpolation, and add up to get the local latitude value. Because Polaris is not strictly in the North Pole, there will be an error of about half a degree in latitude when measuring the elevation of Polaris. In addition, after obtaining the true north, record the time when the sun crosses the true south direction, because Beijing time uses the time of east longitude 120 degrees, and the longitude can be obtained by using the recorded time difference and 12 hours.