Hi guys
I'm doing some coursework for my?ÿfirst year?ÿLand Survey?ÿcourse?ÿand would like to ask you all a quick question. I have to place some control stations on a site and then carry out of traverse. To make the exercise more realistic I'm going to do it at my Dad's place and?ÿafter doing the coursework I'd like to use the stations to do a detail?ÿsurvey of his land and house outline.
I'll turn a few angles at each traverse station and adjust them. Then I'll do the traverse calcs?ÿand?ÿmake bearing and co-ordinate?ÿ corrections.
I'd just like to ask a question or two on the positioning of the stations. By positioning a station (4 in total) on approximately each corner of his site they'll be spaced out by about 45metres and will see each other. However when I come to do the detail work there'll be a few areas on the site that won't be seen by these four points. Should I have extra stations in the control set up so everything on the site (boundary and house) can be seen? This will mean some legs will be only 15 metres.
Or should I introduce a few temporary stations when I do the detail work that will enable me to see everything?
I hope I have explained myself properly.
Best regards, John
?ÿ
Hi John,
I would go with the 4 control points, it keeps your legs balanced.
Add more additional stations when you need for your detail survey.
You can add a traverse leg with multiple points and start and finish on your control points or once you get more experienced you can do a resection.
Keep your control points when you finished your survey, they may come in handy to do resections later.
Succes, you might as well keep us updated and posts your results here.
Greetz from Belglium.
Christof.
Balanced legs are less important with today's precise equipment and more advanced software. Having said that keep your 4 legged traverse, and add additional points (not temporary) where necessary to cover the whole tract. Those points should be visible from 2 of the 4 but not necessarily 2 consecutive TPs. Observe every traverse angle and distance possible, that will be very redundant. Using some but not all observations set up several different paper traverses, least squares same and compare the various sets of traverse coordinates.
Another way of adding redundancy to a traverse is to observe a property corner from 2 different traverse points and not bother to occupy the property corner. See if that pair of ties helps or hurts your traverse.
Paul in PA
It may be a bit early in your education, but least squares analysis is something you should eventually learn, and this popular tool has a free demo (I think limited to ten points).?ÿ Running hypothetical examples with typical measurement tolerances will give estimates of the accuracy of the results, and can teach you a lot about what is important in a control network.?ÿ
With such a tool to do the adjustment, you are not limited to a simple traverse.?ÿ Any measurement you can make can be added to the data set to improve the accuracy of the solution.?ÿ Cross-ties and other redundancy can help a lot.
A short leg is not good for maintaining angular accuracy in a traverse, but in a more complex network that may be overcome by other measurements.
http://microsurvey.com/products/starnet/
wow! thanks guys - that's really helpful advice
Cheers, John
Even with the more precise measuring equipment, strong geometry produces strong results.?ÿ There is error in every measurement.
Go for the 4 main points.?ÿ I happen to like 3 point resections for those pesky intermediate points.?ÿ Setup your first resect where you can see three control points, then setup your second to use the first and two others.
Learn least squares.?ÿ?ÿ
will go for 4 main points. For the intermediate points I'll only be able to see two of the main points as there's too many buildings in the way.
Cheers, John
Take the time to carefully measure the height of the instrument and reflectors (H.I. and H.R.), and record them carefully in your log book (you DO have a log book, I hope). Poor "measure-ups" will introduce error into your network that you will be chasing down for some time. Do it properly, right off the bat. Which textbook(s) are you using?
Take the time to carefully measure the height of the instrument and reflectors (H.I. and H.R.), and record them carefully in your log book (you DO have a log book, I hope). Poor "measure-ups" will introduce error into your network that you will be chasing down for some time. Do it properly, right off the bat. Which textbook(s) are you using?
Nice idea RFC.
Good practice is to measure your HI in both feet and meters, record both in field book.
cheers guys - will measure height as accurately as possible. What method do you use? Most guys I've seen use a simple tape measure but it must introduce a few mm of error.?ÿ The method I'll be using must be able to be done solo.
I'll be doing most of the jobs on my own - have bought a cheap 2nd hand robotic.
oh text book is "Surveying for Engineers" by John Uren and Bill Price. I really like it
John, If your robotic is Leica there is an ingenious bracket and tape measure that measures height of instrument - directly. ?ÿBest wishes on your endeavors.