rfc, post: 356471, member: 8882 wrote: Hey Jerry, Thanks for that link. I must have missed that on the site (although the last time I looked, I was absorbed in Polaris, not Solar). It's inspired me to give the altitude method a try. But I'm going to start with Hour Angle first.
I gotta ask though...When this was used in it's heyday:
Did you even need to worry about the difference between UT1 and UTC?Some people did by applying the double tic info from the WWV signal. Generally just a fraction of a second you would have to decide if it was worth it.
The result of any error can be evaluated by reducing an observation and then altering one of the observables by the amount of estimated error and checking the difference in the result azimuth.
And if you use a stopwatch, how can you reliably punch it to within a tenth of a second?
Do some testing with time tics and see how close you are, then adjust accordingly.You can set the sun's image so that your vertical cross hair leaves a crescent to the edge, take you hand off the horizontal motion and take the time when it becomes tangent. This is why the trailing edge is used, although you may be able to get it on leading edge.
Of course an objective filter is required if using a total station. Many crews had Roleofs prisms which made pointing seem easier and were also a filter. You can get filters for many topcons. If you are using a transit or theodolite you could use the projection method on a piece of paper as see the cross hairs. If you do altitude it is a bit more tricky because it is usually more difficult to get two crosshairs to tangency at the same time.
- jlw
I went to UW-Madison when Ghilani was a doctoral student, and Paul Wolf was my professor - and good friend.
I used the Hour Angle method a lot at the time since I did a lot of field surveying. I found the nested parentheses prone to causing blunders, so I developed both a program for my programmable Casio calculators and wrote a Pascal program for PCs (checked by both Paul and Chuck). The programs even averaged the shots and figured standard deviation, which I found to be typically 6 seconds of arc.
Time was easy - since I was a short wave addict, a WWV 9v time cube was just the ticket.
Probably not as fast in the field as Burt's solar transit, but I was a mere student in the shadow of those two greats.
Now I'm a mere student in the shadow of lots more Greats - expanded horizons.