Land Surveyor Forum

Replies

• Survey Legend

  ⚡Survenator⌁ August 18, 2020 at 7:24pm

  Great discussion!
• 

  Bradie Brackman May 31, 2015 at 1:13pm

  Try using blockouts on grid line or grid line o/s intersections. Create your control lines on the first elevation and place blockouts on next elevation at same intersections. There are targets made for this process but I use plexi glass. Using a PLS (you will likely need a second person) place the PLS on each point and rotate to each quadrant and mark accordingly on the plexi glass above. This will create a crosshair that takes out any error in your pls. Using a 1/16 or 1/8 drill bit drill the CL of the crosshairs. I have used this method up through 28 levels going to 31 very successfully. Now when you set up on that level you use the drill points to set your prism pole.
• 

  Lalith Senanayake March 16, 2014 at 4:23am

  Chamara,
  See my above reply regarding this
• 

  Lalith Senanayake February 15, 2014 at 7:29am

  If the the point you are going to fix,is on the circle passing through the three control points there are many points on the circle,and there is an ambiguity
  http://en.wikipedia.org/wiki/Resection_(orientation)
  Please see
  Cheers!
  Lalith
  • 

    Lalith Senanayake > Lalith Senanayake February 15, 2014 at 8:24am

    Caution: When planning to perform a resection, the surveyor must first plot the locations of the known points along with the approximate unknown point of observation. If all points, including the unknown point, lie close to a circle that can be placed on all four points, then there is no solution or the high risk of an erroneous solution. This is known as observing on the “danger circle”. The poor solution stems from the property of a chord subtending equal angles to any other point on the circle.
    • 

      Chamara Prasanna > Lalith Senanayake March 16, 2014 at 3:05am

      I think we don't want to consider "danger circle" if we used resection by distance method.Should Only  consider when doing resection by angle which is not very common.
    • 

      Ivan > Lalith Senanayake February 16, 2014 at 8:05am

      Hi,

      The rule of thumb to do Resection the angle between GCP must be minimum 45 degrees

      I use to do minimum 90 and if possible more than 135.
• 

  Don Best February 13, 2014 at 6:51pm

  Two assumptions to start with:

  1. This is a steel structure and your concern is STRAIGHT UP.

  2. You have "quality control checked"  and know exactly where horizontally your steel columns are setting     to the nearest hundredth. AND you have reviewed your "asbuilt" findings with the project

      superintendent. This takes care of your "CYA". OK!

  Once the bottom floor columns are in place, FORGET ABOUT GROUND CONTROL--DON'T EVER

  GO THERE AGAIN.

  Most vertical steel columns come in "two-floor" increments with a splice just above the 2nd floor.

  On the ground floor set a TOPCON prismless total station on your tripod. Remove the eye piece and

  attach a 90 degree eye in its place. With out this equipment----forget it---your not going to get the job done. Once done with the ground floor set-ups get rid of the tripod also.

  Here is your process. Assuming they are erecting sections of the building of about 3 columns wide

  by 5 columns depth and remember it is two floors at a time vertically.

  Set your tripod and Total station on the ground floor just off line with the nearest column your shooting in

  the row of 5 columns such that you can see part of the flange of each column AND you can see the bottom of each column and the top of each column just below the splice--WARNING: make sure you are

  not shooting the splice plate----only the column flange. Level up your insturment and your ready to go.

  Get an 8 1/2 by 11 sheet of paper on a clip board with the column symbols laid out with plenty of space

  between for shot notes. Be sure to properly label this sheet AND never let it get away from you---give out only copies to the steel workers and your boss.

  You will be recording shots twice: once on the intitial erection AND on a clean sheet for the final asbuilt

  when the steel crew is "cranking" the adjustment cables. The steel crew will use your first shot record

  to determine where they need to erect adjustment cables. You aim the gun just a few inches above its base and lock the horizontal; then shoot the flange by pushing the H DISTANCE button on the gun. record

  the average of several shots. then carefully raise the scope without moving the horizontal to just below the splice plate (two floors up). This probably should not be more than about 45 degrees off horizontal. Now

  push your DISTANCE button several times and record the distance; It will be either closer to you at the top or farther from you. Now unlock your horizontal and put your vertical eye hair at the edge of the flange

  near your top shot and lock the horizontal; then lower the scope to the base; have someone put a tape aganst the edge of the flange and read it through your scope: that is how far it must move in the perpendicular direction at the top. Be sure to record this just in case the steel crew doesn't want to move it---show it to the boss---it will mess you up going on up.

  Now! Once off the ground floor have the steel workers  cut you two 3x3 angle irons 

  that have bolt holes to attach to any column with a welded plate to mount the gun too.

  Be sure to give yourself about 1 1/2 foot from the center of the gun to the near edge of

  the flange. Just keep doing this as you go up---over and over. Have fun.
  • 

    Ivan > Don Best February 14, 2014 at 7:08am

    Good morning,

    Another way, a little less complicated, can be RESECTION on each floor using your Total Station, just be sure the Ground Control Points are VERY GOOD, this is maximum 3 mm Residual difference and 1" angle residual difference, check all your GCP, then you can set your Control Points on top of the adjacent buildings and GO...
    • 

      Lalith Senanayake > Ivan February 14, 2014 at 8:25am

      Yes but three contol point shoud not be ondanger circle,as I have stated above reflector-less or any prism placed at a point will not give us 3mm accuracy,best way to read off the mm tape with swing to read the minimum reading