Mike I saw your post and it look like you want to learn surveying. You had a nice diagram showing points you want to establish along with
known points.
First I would like to say you need a better North arrow. When I looked at it, it looks like a 7 N; also under the North arrow you should have
NOT TO SCALE, or put the scale of your drawing (plat) on it.
I have many questions for you. Have you observed angles before? Has the surveyor you use taught you how to observe? What type of Instrument does he use? What type of instrument are you going to use? Is the instrument calibrated? Is the EDM calibrated? Have you done work in the field with a surveyor before? Have you looked at "Classification, Standards of Accuracy, and General Specifications of Geodetic Control Surveys"? (you can find this at NGS web site. This publication will tell you the field requirements (number of angles to turn etc. for 1st, 2nd or 3rd order work; traverse in your case).
After you answer all the above I still have more and some helpful suggestions for you.
JOHN NOLTON
Tombstone, AZ
Hey John - thanks for replying! I gulped when I saw the thread because I assumed I was going to get scolded again, so thank you for not doing that! For everyone, I apologize if I stepped on your turf. All I can say is I intend no malevolent purposes, and that having a basic understanding, and gaining confidence in my observations, its both interesting to me and incredibly useful. Lots of things I can use it for that don't require a seal.
My equipment: trimble sps930; at360; two leica gpr121's and high precision carriers w/ opt. plummets; a trio of leica 5000 series tribrachs; trimax tripods and trimble's adjustable pole w/ bipod stand. Most recent shop calibration 4 months ago. Compensator is still correcting for less than 5" - I do the full compensator, HA/VA (currently about 2-3" in both H and V), trunnion (about 7"), and tracker collimination before starting. Pole gets adjusted w/ plumb bob jig and the carriers are adjusted according to regular plummet sighting tests. I haven't done an NGS baseline test yet. I did try, though. Despite the NGS site's records of the baseline, I drove over and there's so much overgrowth it was unusable. I've repeated AB+BC / AC tests - satisfactory.
In traverses, I've done rounds in F1/F2 with 3 observations in each face, two rounds for the mean average. I'm setting up, leveling, and sighting my nails as meticulously as I can. I'm in no rush.
The engineer's crew - I'm not sure what they used, but it looked like Topcom, non-robotic, hand held pole. I can't tell how many points of the 5 control points they brought in by GPS, maybe 2 or maybe all 5. About 4,400 topo shots in 2 or 3 days. I have the point file.
I've read the NGS manual you referenced, although all of my distances are much shorter - about 300' - 600' average, longest about 1400'.
Honestly, the catalyst for buying my equipment was watching the crew work. I had air-probed down to utility lines and was watching them pick up my stakes. The pole man was holding the pole about 4" in front of my stake, and I asked if the prism was offset that much (what did I know?). He replied, "Nope, right at the center of the pole." Took the measurement and went on, and I thought, "Hmmm, Ok..." Of course the file's topo point is 4" off my stake, and it goes on from there.
Like I mentioned before, on my test traverses, I can go home, come back, and repeat resection and stake out tests until I'm beat and, even considering how much all of this equipment costs, I was really impressed. Pretty exciting. The site I attached on that sketch had a traverse length of about 5,000' with 6 corners; I got a raw misclosure of N 0.006, E 0.011 and Z 0.019. I don't know how to benchmark how good of a job I did, but I've been able to re-setup or resection, and accurately stake my points. If I try any of this on their points, I don't come close.
Summing this all up - none of my "exercises" have an impact on the practical implications on this job. Everything is still within the tolerance that any construction crew would care to do on a pipe job, and I'll be pulling tape like I always have (which is simple here since everything is offset parallel to sidewalks and within very short distances). Though it's been exercising my brain...
Sorry if I should have been posting this in the Construction or Beginner's forums, just I didn't know how many people check those. Let me know if you prefer I take my posts there.
Also, I'm not fishing for answers to why it would appear I can't retrace their points - I know there could be any number of factors, including, I believe it's called beer-thirty. Nothing about the project requirements specified that they needed higher accuracies, and they did do a lot of work fairly quickly.
Finally, regarding lessons from my *actual* surveyor - I haven't forced his hand yet. He's a really nice guy but uses different equipment from me, so I wanted to have a better handle on the Trimble ecosystem first.
Sounds like I'd hire you.
Good work.
Scott Zelenak, post: 373178, member: 327 wrote: Sounds like I'd hire you.
Good work.
Wow. Extremely HIGH (WTC height) praise.
Mike J.
Glad you came back. Since you have time and are trying to learn I would do the following. Ref. to your sketch you 1st posted;
I would place point "a" on line with point 1 and point 2, point "b" on line with #3 and #4, point "c" on line with #5 and #6 and point "d" on line with
#1 and #6.
1. Since you have some longer distances this will not make (or should not make) to much difference but its FOUR angles LESS you have to turn
and this will make a difference in the adjustment .Way less time is spent to put them on line that turning angles at each point.
2. If this was short distances it will make a big difference in your angles and distances and closure.
Since you are still in the testing phase (your skills and equipment) I would use the following procedure when turning angles.
Turn at least 4 D&R, change the plate reading each time you measure a set. And the last thing is "close the horizon".
Now closing the horizon will test you ability on how well you point and tell you immediately (in the field) if you have a good angle or not.
So lets go back to your sketch and say you are setting on point #1. You want to turn the angle from #2 to #6.
Your record book will have :
You look at point #2 and read D 0 0 30 (for 0 deg 0 min 30 seconds +/- 10 seconds (see NGS publications I referenced before) for circle settings.
You then turn the instrument to the right (clockwise) and look at point #6; record that reading, you then plunge the scope and turn the inst counterclockwise and point back on #6. Record that reading. You then continue to turn counterclockwise and point at point #1. This is ONE SET. Do this 3 more times.
By the book for 3rd order Traverse Class 1 you need to do 4 D&R (Station angle). I want you to turn the explement angle so you could cut this to 2 D&R, but do 4 for practice. Now for closing the horizon (explement angle). Setting on point #1 you now set your first circle setting looking at point #6; turn clockwise to point #2. Plunge the scope and turn counterclockwise to point #2 record value; continue to turn counter clockwise to point # 6 record value: This will give you 1 set of explement angle.
When you take the mean of the station angle (x number of times you turn it) and ADD it to your explement angle ( turn it the same number of times you turn the station angle, x times) you should get 360 dergees (that's if you were in the degree mode, 400 grads in the grad mode or 6400 mil in the mil mode, If you inst lets you use different modes).
How to set points on line. Two different way and you should do both ways for practice.
One is to set at point #1 look at point number #2 and have a helper take line from you for point "a"; remember you must use both D &R for this.
The other way is what is sometimes called wiggling in or balancing in. You put up a target at both points #1 and #2. You then go to where you want to set point "a". Set up your instrument as close to being on line as you can. You sight say point#1 plunge the scope and look at point #2. Note how much you are off. You then slide the instrument on the head of the tripod, level up again and do this till when you plunge the scope you are very close.
To get exact as possible you will look at your station #1 in both D &R. What I mean by this is; you look at point #1 plunge the scope and look at point #2 (lets say you are very close) you must look at point #1 in the reverse mode and plunge the scope and look at point #2 and see how much you are off. Since no instrument is in perfect adjustment you will have a split. You want the same amount of distance you miss the target at point #2 to be left of the target as you want it to be to the right of the target (your split in the instrument).
Try this in the field and let me know how you do.
JOHN NOLTON
PS When you measure your distances measure both ways and make sure you take pressure and temperature and correct for it. Some instruments will take T&P but I do not know which ones.
Mike J.
Do not forget to take some classes in surveying if you can find them in your area. Its much easier for a instructor to explain the above on the black board
and with a instrument set up than my post above. Let me know if it was clear.
JOHN NOLTON
