LandHO,
I suggest that you get a piece of white paper and focus the eyepiece on the paper so that the sun is visible and focused on the paper, along with the cross hairs and shoot your solar shot that way so you won't need a filter. Or for several hundred dollars you can find a used transit and do the same thing if you are worried about sunlight messing up your total station EDM.
You can obviously observe Polaris without a filter.
The procedures for doing this are not rocket science, and based upon your stated credentials this is something you should be able to do with a little practice.
If you observe Polaris and don't have extremely accurate time (which is not expensive to obtain), calculate when Polaris is at eastern or western elongation and shoot it then. The east-west movement rate is less during that time, therefore time is not as critical as it would be on upper or lower culmination.
Forget cell phone trying to use GPS to do that. Not accurate enough.
Mr. Land Ho seems to be interested in making a tradeoff between spending cash and using his own time. To take it to the no cash, lots of time end of the spectrum, he could use the moon. That would eliminate the expense of a filter. By choosing a suitable time, he could shoot the moon when it is fairly low in the sky, eliminating the need for a right-angle eyepiece attachment. He might find the USNO's free table generator at http://aa.usno.navy.mil/data/docs/AltAz.php good enough to find a monument after traversing 700 feet, even though it is only to the nearest 0.1 degree.
He could explore some of his questions about how good the time or latitude and longitude need to be by plugging different values into the table generator and seeing how much difference it makes.
Considering the table accuracy is only 0.1 degree, it might suffice to identify a feature near the center of the moon and aim at that, rather than having to calculate the effect of aiming at the edge of the moon.
The USNO site also offers the Multi-Year Computer Interactive Almanac for $30 which is much more accurate and flexible than the tables available on the website.
> The USNO site also offers the Multi-Year Computer Interactive Almanac for $30 which is much more accurate and flexible than the tables available on the website.
i'm thumbs up on mica software, it does everything but the observations. many different functions, sky maps, major events,many different flavors of ephemerides, occultations, rise/set/transit tables, etc.
Thought it over, and here's my conclusion: Mr LandHo doesn't need a bearing at all, he needs to random over from one of the set mons to the other and then true back to mark the line. No need for GPS or azimuths or any of that stuff.
Wow. All the input I have received has been great. I really do appreciate it. Nate even set up a new thread for LandHo - how about that!
As with any neophyte, I started out thinking I needed to do one thing (get an accurate fix on North), was shown I could do what I needed to do using many other techniques. Ended up learning a lot of useful and interesting stuff, and got excited about doing some of it if not just for fun. The nights have been great for star viewing, other than the -20F temps. So for now I'm staying in and reading up on this stuff and spending way more time on this forum than I should.
Thanks to everyone!
(To me) you just gotta do a solar observation just for the fun of it. It is just really cool to get your own bearing off of a big white star that you can't even look at with your bare eyes as it sails across the sky. It makes me want to do one every time I'm out there.
The first one I had done on the job, I worked for a company that was all snooty and said they only did other stellar shots. They didn't want some poor basis of bearing off the sun. I was the 'instrument man' on a crew, and we were doing a job in the mountains. I was set up on a tripod and we were waiting for the third crew member to set up a foresight for us. (he had to drive down the mountain and up another trail to a traverse point location we had already established) I had been reading up and practicing on solar shots and asked the crew chief if he would take notes. I turned four sets of angles projected on a piece of paper and clocked the time with my hp41cx which was adjusted to the atomic clock. We just threw the readings and calculations right in the notebook and turned in our work at the office. The project manager (pls) saw our calculations and projected the line over to another line they had done a polaris measurement from a few years earlier, and he matched the bearing within a couple of seconds. The company became convinced after that, that solars were a viable method for bearing measurement.
Glad you are enjoying the surveyors' discussions. My past experience with a lot of engineers is a bit of a superior attitude making it hard to even communicate with them. (Fortunately I have mellowed out from my superior attitude 😉 .)
That's how I have always done it when successive monuments were not intervisible, which is often the case on larger parcels in the California foothills and mountains. Once you run between them using a random traverse, you can occupy one end and turn the angle needed to put you on line, regardless of the bearing or what it is referenced to.
You don't need to know where you're going if you know how to get there!
> You don't need to know where you're going if you know how to get there!
That's because if you don't know where you're going, any road will get you there.
Let's just figure it out on the way!
No, it is not important to PRESERVE the record
It is important to RETRACE the record.
It is important to understand the GIS that is being created, and what others are doing.
OFTEN the GIS guys are LOOKING for an objective BOB, and will rotate whole neighborhoods to SPC, or Quasi SPC, just to assemble the neighborhood.
I think it is an enlightening experience to GO AND SEE what is happening down at the REAL ESTATE tax office. They are actually compiling deeds, and plotting whole towns, and they often have somebody that knows how to do this down there. That is WHERE your issues will show up.
Objective BOB is where we are going. There are basackawards towns, and there are some that are AHEAD of the surveying profession.
Nate
HEY I RESEMBLE THAT REMARK!!!
For observing Polaris for azimuth your smartphone lat/long should be accurate enough (assuming you are using it out in the open, not inside or in a forest).
For observing Polaris time only needs to be within a minute or so of UTC.
Typical astro ephemerides give positions at UTC midnight once per day. You need to interpolate to the time of your observation.
Any standard Elementary Surveying text should include instructions for how to observe polaris and how to do the calculations including the interpolation mentioned above. If you set up an Excel worksheet to do the calculations you can input different times and different lat/longs to get a feel for how the answer changes. Achieving 1' of azimuth is not difficult.
Polaris is roughly your latitude above the horizon. For me that is almost 39° so I am able to get by without a right angle eyepiece. If you want to observe Polaris in daylight then it is helpful to know where infinity is on your focus ring.
A roeloffs is the way to go if you can get one.
Never point a total station at the sun without an objective solar filter unless you aren't planning to use the EDM again.
