@ chris-bouffard
It seems to me that, based on the method mandated, the mandate for the procedure was dictated by office staff.
It was not. We thought it might speed things up.
Was it really necessary to send somebody ahead with GPS/GNSS equipment to stake to a line that was predetermined by office calcs, or, could that have been easily been accomplished by either pacing or slap chaining distances between turning points?
It was easier and more efficient than pacing. There were no office calcs.
Are a few feet of distance between back and fore readings going to change the results?
Certainly not. FGCC (1984) third order leveling specifies difference of forward and backward sight lengths never to exceed 10 m per setup and 10 m per section. I think that's been supersede by standards that address digital leveling.
@ chris-bouffard
Those three BMs now have multiple elevations on them.”
What purpose does adding yet another elevation serve?
See Surveying Theory and Practice, Davis and Foote, Sixth Edition p. 172. Specifically, 5.51 Adjustment of levels over different routes. I need to learn how to do this.
You're missing my question.
Hey so make yourself a copy of the digital files and level notes. Sign up for the next NGS geodetic leveling course. Great class. It has been 14 years since I attended one. But what you learn a lot. One thing is you have a closure good. And your balanced distances check the requirements. Now apply the orthometric corrections adjust it etc. c/r corrections temp corrections. Once done you have it going on. Until then it’s just difference in heights. Great job . So were you on level crew Iman two rod persons . Leveling is an art. I spoke with several that’s all they did every day. Man they were a unit. They have that leveling class twice a year. Spring and fall. So around October. If you can come message me i will make sure to buy you a beer. They tried the virtual thing but it is better when you spend the week doing field and office. You can probably watch the online and get the corrections and adjustments part down maybe compare to the office results. All the programs from NGS software is free so are the classes. Make your boss send you if they can.
Reminded me of Topcon's Z-Plus rover that has a base station with inclinometer, unfortunately it's Japanese market only, I've been keeping an eye on online auctions, in the hopes of getting one. The first thing I'd do is ask our local rep to send it away for calibration, just to get Topcon thinking about selling them in other markets.
@ chris-bouffard
The last time I spoke with my field crew supervisor concerning multiple elevations on BMs from the other run he said he's going to average those elevations. We're in the process of connecting different runs throughout our county. Sorry for the misunderstanding. Thanks for participating in the discussion.
@ OleManRiver
So were you on level crew Iman two rod persons .
No. PC, I-man (me), rod person.
If you can come message me i will make sure to buy you a beer.
I like Heineken dark lager. You?
I like a dark beer myself. Yeah. If you ever do get over my way. I have you covered.
What kind of differences are you seeing between published and observed values? A few hundredths, or tenths?
Russian Imperial Stout
So here is a secret. Tell him not to average them but to perform a least squares after he has applied all the other corrections. All those BM’s you ran through if they were NGS monuments should have an uncertainties on the data sheet. This would be following more closely to blue booking geodetic leveling Have him come with in the fall to the NGS leveling class.
Next thing is when you have longer level runs. Have at minimum two rods and Rodman. I guy running the level. This will push you easily to the 3 miles in a day vs 3 days. Once the crew has there rythem you will look like a well rehearsed play on a stage. Smooth as silk. A good crew when use to each other and all are on their game can average 5 miles a day. But that is with a crew that is seasoned in that work.
I do like a good stoute. Or a porter lager etc.
@ chris-bouffard
What kind of differences are you seeing between published and observed values? A few hundredths, or tenths?
Pt. # 1134, 0.035' difference, 271.6' from beginning BM
Pt. # 1136, 0.014' difference, 5608.6' from beginning BM
Pt. # 1137, 0.009' difference, 8473.4' from beginning BM
Thanks, that satisfies my curiosity, in the end, one or two hundredths are not going to be earth shattering.
Are they all positive or negative or do they go both ways. Also those monuments were they all part of a single run originally or was some set from a different run and direction of the level line.
@ OleManRiver
Are they all positive or negative or do they go both ways.
Pt. # 1134, 0.035′ difference, 271.6′ from beginning BM
Field El. = 96.760 Published El. = 96.725
Pt. # 1136, 0.014′ difference, 5608.6′ from beginning BM
Field El. = 96.407 Published El. = 96.393
Pt. # 1137, 0.009′ difference, 8473.4′ from beginning BM
Field El. = 101.240 Published El. = 101.231
Also those monuments were they all part of a single run originally or was some set from a different run and direction of the level line.
The monuments are all part of a single run.
So all in one direction. That except the one outlier could be systematic in the rod itself. One piece rod or two piece rod. NGS has a published document on rod errors for digital levels. I can’t recall all of it and could be mixing a few different studies I have read old age every thing gets jumbled sometimes in my small brain lol. But two piece rods the error can be seen more in certain heights that are read along the bar . I still thank you did a terrific job and whoever was the Rodman you need to buy them lunch. In my opinion the Rodman on level runs is the most important job for accuracy. It is boring and easy to get distracted as it seems so simple. But a good Rodman is always focused on setting that rod exactly on the highest point for readings and keeping a good plumb rod etc. I use to think a Rodman watching them was like watching T-BAll kids in the outfield. Gazing all around throwing dust or grass in the air. I had a few Marines I had to watch like a hawk. It is a role that requires discipline for sure. I could teach anyone to push the button on the level to read it and yeah even reading old school the 3 wires you had a check . We used turtles a lot for turning points and it never failed the first day out one of the Rodman would pick up his turtle before we could take a BS. When you are looking at 5 to 10 miles total and you go only a few turns and that happens you know it’s not a good start. Keep doing well man keep learning. Hope to see you out this way sometime or maybe I will get a chance to head your way one day. Wherever that is.