I would try to use a theodolite. If you center it on the first point and know the azimuth to a distant reference, I guess you can determine where the second post needs to be.
Dan Uza On Tue, Sep 11, 2018 at 10:48 PM Dan-George Uza <cerculdest...@gmail.com> wrote: > In my experience, cellphone compasses are completely unreliable for > dialling. Some are off by more than 20 degrees. You can quickly check the > accuracy on Google Maps: the narrower the blue cone is, the more accurate > results will be. > > Dan Uza > > On Tue, Sep 11, 2018 at 10:39 PM Steve Lelievre < > steve.lelievre.can...@gmail.com> wrote: > >> Hi everyone, >> >> How good is a cell phone compass? I mean, if I have no metal nearby and >> I have the phone set to show True North, what kind of accuracy can I >> expect if I lay my phone flat and use the compass app? >> >> I'm working on a vertical west sundial for a community garden (a.k.a >> allotment) and have a deadline of end of September to get it installed, >> because the aim is to unveil it at the group's annual meeting. >> >> The dial is to be installed on two posts. I want to get the posts lined >> up as close to north-south as I can, to make aligning the dial easier. I >> will use adjustable bolts to fix the dial to the posts, so can I >> compensate for the line between them being a couple of degrees off - but >> no more than that. >> >> I already have one post installed and concreted in place. I had hoped to >> use the sun's meridian shadow cast by it to give me a precise line N-S >> for placing the second post. Unfortunately, rain has set in here and it >> looks as if there will not be a sunny day for at least a week. I don't >> think I can wait that long to get the second post installed; otherwise >> I'll be short of time for the other remaining tasks. Hence my interest >> in using my phone compass for alignment. >> >> Cheers, >> >> Steve >> >> >> >> >> >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >>
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