new member with a transit question
What Bill said.
The direction of a section line is determined by monuments. In many counties there are records of them, usually but not always kept by the County Surveyor. They were set by compass in the first place, perhaps 100 to 150 years ago, depending on what part of the country you're in. But the monuments control after that.
You need to find official monuments at both ends of the line you want to run. A compass bearing will not be accurate enough to run a fence line. The fence might end up 20 feet into the neighbor's property.
Here's a manual for the instrument. It does have an internal drawing (p. 5) showing the light path, but it's not easy to read. It won't necessarily help you figure out why it won't rotate a full 360 degrees. Starting on Page 12 there are some tests that will show you whether the instrument is properly adjusted. But actually making the adjustments takes some experience. You might be better off just allowing for the error.
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thanks for the manual. A paper copy came with mine but it is in bad shape. Also, it is a TM-20A manual and does not have the internal drawing. It is helpful. I believe i see a small ball bearing that the upper base would use to spin when the lower base is locked. I am always hesitant to disassemble something like this because it could have preloaded bearings that would get out of sorts if disturbed. I've seen that happen with other things and the bearings tend to lock up. Which is what this one might be doing.
I've spent some time scratching my head over the section line. I have a friend who was the county engineer here. I'm going to discuss this with him.
