A better way to measure HI?

On a Trimble S6, they have the option of measuring the "slant" HI distance to either the scope axis point on the robot or to the bottom notch also located on the side of the robot. Trimble Access converts the slant to a vertical distance in the TSC2.

I still use a new 6' Lufkim or Rhino ruler that is more rigid than the pocket tape. I keep one in the box just for that purpose. If it starts to losen up, I replace it.

I have used the Remote Benchmark in SurvCE with my Leica 1203 and had decent results.

Bob

Pocket rods can be helpful, there are many options.

You could also change procedures so that you never need to measure the HI of your Total Station.

(in other words, I agree with Bob)

I also use carlson with a topcon robot, Colin.Seems that the old SMI program written by Stanley Trent had it right. No hight of pole or HI needed, it established a reference elev. at the instrument and as long as the rod stayed the same right everything worked fine. I always thought it looked hokey using a $20,000 instrument and measuring up with a $3 stick rule. I will give your idea a try with 0 rod height.

Oops! Ment to say ZERO HI

You could do some playing around to come up with the distance from the bottom of the handle under the tri-pod to the center of scope. Then you can make an easier measurement from the ground to the handle and add the two. Much more accurate when all things are measured on plum.

How about a fairly stiff box tape, with a jig that mounts on the end, to square it up, and it hangs plumb, but takes it's point of measurement from a point 8" - 10" offset. To the side. Call it an HI Tape

N

> You could do some playing around to come up with the distance from the bottom of the handle under the tri-pod to the center of scope.

The tripod screw engages the bottom plate of the tribrach, which sits below the adjustment screws, so the distance from the tripod screw to the horizontal axis isn't constant.

I was thinking the same thing, but wonder how much variation we're talking about in the hands of somebody who's set up a gun hundreds or thousands of times. I can't imagine it's more than a hundredth, maybe two. But my curiosity is now piqued and I might just do some incidental measurements for a while and see.

> I still use a new 6' Lufkin (folding ruler).... that is more rigid than the pocket tape.... If it starts to loosen up, I replace it.
:good:

I do it 99% of the time, usually doing a resection with 2-3 points for construction. Plop the tripod down where I can see everything, don't care what the elevation of the ground there is.

Don't ............... with RTK GPS but with robot Yes

On most day to day jobs I measure Hi over some point talking
robot

Most 99% GPS is the "Here" then localize to some sort of site monuments

Only on the most picky job I just force or adjust by say changing a HI from
2.011 to say 2.025 robot or GPS base to the accepted/agree 25 million dollar
project datum.

Bottom line use what works for the job site precision required.

ie measure HI or set Hi to agree with site Benchmark

Peter K

use slant heights at the gun and at your tripod mounted BS and fs. you can estimate to the .005 and correct up. works pretty good. you'll see it come in when you do your least squares adjustments.

Set your tripod up first and set it up level over the point.
Then measure down through the hole to get the height of the tripod.
After setting up the instrument and getting it level and prescisely over the point add the distance from the top of the tripod to the horizontal axis.
It's easier done than said.

Since accurate total station survey elevations depend not only upon accurate HI, VA and SD measures, but also accurate HS (HT) measures, the corresponding question on better ways to measure HS (or HT) should also be asked.

A tripod-mounted prism has similar geometry to a total station setup but a pole-mounted prism has a slightly different geometry. Many poles have impressive-looking graduations along them but i never knew how to use them when they're telescopic. Does anyone? And is the zero where the sharp point used to be when new or where it has now worn down to?

If we pretend both HI and HS are zero as suggested above (or just made equal) the question is now on better ways to make HS equal to HI.

> ...SurvCE has "Remote Benchmark" - You shoot a good BM (on both faces, which is good) and it back calcs an elevation for the instrument point.
I once worked with a guy who would figure out his HI by shooting the BS, which had a rod of known height on it, and backing the HI in that way. It wasn't approved procedure, but it never caused any trouble. Luckily. His BS checks were always perfect for elevation.

> Many poles have impressive-looking graduations along them but i never knew how to use them when they're telescopic. Does anyone? And is the zero where the sharp point used to be when new or where it has now worn down to?

I use the graduations daily. I check the pole periodically for point wear, and sharpen the point when it gets too dull to stay on a small punch mark. I keep the graduations current via shim washer(s) between the point and the pole. Right now I have a washer in there that's 0.005' thick. I'll shim as far as 0.01', and install a new point when that no longer takes up the slack.

We are surveyors

We are surveyors. We carry calculators.
Measure the hypotenuse, and the offset.

🙂

N

Yes exactly.

S6
Folding 6' ruler
Slant measure mark

Don't over think it, dude. 😉