The Promark2 is listed in specs with about 0.039 precision+/-.

In Ohio, a distance measured must be 1:5000 MINIMUM.

This means that if I I'm locating pins, my measurement accuracy for a 100' lot must be "MINIMUM" of 0.02.

Does anyone use Promark2's for surveying boundaries. If so, have you seen "discreptancies" in location?

Work to change those standards. That's lame. In Texas we are given 1:10000 +/-0.10' in urban, 1:7500 +/-.010' in ETJ and 1:5000 +/-0.10' in rural. I am continually impressed by this scheme. If I survey a 50' lot, I am not stuck at having to meet some impractical standard.

That said, yes we have used the PM2 for boundary work. Only rarely though as the conditions here just are generally not favorable for it.

If your colleagues are using RTK for boundary, I would not think that the PM2 would give any poorer results than that. I may be wrong, but as I understand it, RTK on short lines uses the L1 for the solution just like the post processed PM2. It just isn't real time or OTF.

Shawn

let me pile on here...a 5 second total station generally has an EDM that is good for 5mm +/- 5ppm...5mm is about 0.016', so unless one is capable of minimizing set-up error to nothing, 0.02' on a 100 foot baseline is going to be very difficult to achieve...

kinematic GPS is more than adequate for boundary work, given proper conditions...and depending on the total station you use, it is likely as or more accurate...

I must say, I like that idea.

Actually in Ohio, I think we're given an allownace of 0.01 for the plummet, 0.01 for the centering over the point(that's a possible 0.02' so far), then our accuracy of measurement. You se we are a little more liberal than I let on originally.


BUT THEN, when the Promark specs call for 0.039+/-, could it really mean that between two points, if you were a little on the unlucky side of life, that you could miss point 1 by 0.039East, while missing the 2nd point by 0.039'West. Or, a total of about 0.08'?

I wonder how "random" the 0.039' error tends to be.

John,

Set your "base" in the open 1,000 feet away from the project. Kinematic the project. Now you have beat the accuracy specs. Orient your antennas the same direction if you'd like.
I see things like this: the GPS satellites orbit at 20,000km above the surface of the Earth, and here we are trying to measure a 100' distance. How many stake tacks can you set in the top of a match stick, much less measure between them?
Modified By Dave Huff on 12/2/2003 at 7:08 PM

Generally the state law precision ratios apply between adjacent monuments. Setting the base 1000' away won't fix that, and in fact will make it worse as the baseline ppm comes into play.

SHG

I see 1 ppm as 0.000001

I see 10 ppm as 0.00001

I see 10 ppm in 1,000 feet as 0.01 feet.

If John is having a really bad day, and he is 0.039' out in opposite directions then with the 10 ppm we got

2(0.039) + 0.01 = 0.0880 feet

1,000/0.0880 = 1 In 11,364 more or less.

2,000 foot baseline, same ppm, same error at each end gives 1 In 20,408 more or less.

Am I correct?

Sure, but what about those two pins I located that were 100' away from one-another.

Such that I go to pin A and my error "happens" to be 0.039'west, then I go to pin B and my error "happens" to be 0.039'east.

If the pins were placed "exactly" 100.000000000' away from one-another, my GPS would be reporting either 100.08' or 99.92' . . . eh?

$9.99 a minute. No kinky stuff. I need to pay the rent. Shall we continue??

;) Dave

redundancy, redundancy, redundancy




then shoot them again

gps ain't the fix all, do all for everything.

I wouldn't trust the top of the line RTK system for boundary work without repeat obs on EVERY point! So, that must also include post processed stop and go kinematic, regardless of the brand name.

Remember the key to these extremely short duration gps obs is provable repeatability. And that, by necessity, means under different constellation and conditions. You have to be the judge as to whether or not the tool is right for the particular job. It's your license!

j.d.

did I say redundancy????

did I spell "redundancy" correctly??

and if they really count, what's wrong with 5-10 minute obs on the "serious" stuff.....with redundancy as well.

IF it make a difference to not run conventional into those hard to access boundary points, then gps obs (with proper redundancy) makes one heck of a lot of sense.

I really think it's worth repeating again another time....redundancy

Redundancy is a must for boundary work.

Redundancy with GPS (RTK or Stop 'n Go) means a second observation at a different time of day so a different satellite constellation is in play.

For those of you contemplating two base stations to deliver two simultaneous vectors to each rover point, note that running two base stations provides you with diddly squat as an independent check since the errors in each vector will be highly correlated (ie, multipath). You'd be better of to reobserve each point at least one half hour later using the same base station.

The two base method does work as insurance in case of problems with the data from one of the bases.

JD kind of skirted around the 'redundancy' issue in his posts so I thought I'd emphasis it a bit ;-).

Having said all that, the repeatable accuracies for Stop 'n Go kinematic should deliver 2cm + 2ppm if sound field procedures are used.

Modified By Scott Partridge on 12/3/2003 at 12:35 AM

Scott,

Quit dilly dallying around the issue. Redundancy is the key here.

Am I correct in thinking that pp stop and go (L1) gives the same accuracy as RTK (over short distances)? I really don't know, but am just putting together what I have picked up from various places.

Shawn

2cm's in my book is quite a bit for boundary work. Especially if your lot is only, say, 200 x 400

I wonder if this question is part of the reason why I've had nightmares(bad dreams/keeping me awake), about using the Promarks.

They would never work. Either the metal of the 2-meter pole would be wrong, the sun would be in the wrong place, or north wasn't where it was supposed to be. But anyway, in my dream, imagine being in a pea-green fog, in the swamp, and setting these units up. Now imagine the "hounds of the baskervilles"(similar setting).

Anyway, it's a bad dream and I've been tossing and turning over this now for three nights. I wonder what it means and I hope to hell I get it resolved.

Modified By John Francis on 12/3/2003 at 10:52 AM

John,

I wouldn't consider using the GPS equipment (static or kinematic) to survey a 200' by 400' lot. Thats what the TS is for. Too many concerns about multi-path from buildings and trees and the TS is more efficient. But if I had to tie that survey to to a control point that was difficult to traverse to, I'd use GPS if it was quicker and saved several setups with the TS.

You have to pick your spots for each.

On boundary work I set the primary traverse with static GPS and usually make the ties with a TS. If I make distance-distance tie, I set three points and tape between them and to the point I'm locating. If an acreage job has too much cover, a conventional traverse is better. On long lines through heavy cover, I set a static point in the open at each end and traverse between them.

I've tried kinematic for traversing but found it to be not efficient due to down time from loss of lock (a lot of tree cover in PA). I've only had good success in the winter without the leaves.

Three PM2's were half the price I paid for the TS. One-quarter the cost in todays dollars. I don't expect them to work miracles.

Del

Good points Del. I agree with all you said. I wouldn't use it for the small 'lots' either. If you are wanting to do work solo, buy a bipod for the prism pole and driveway reflectors for topo shots. Combined with a reflectorless gun I think you are WAY better off than trying to kinematic in those smaller jobs. I know John already does this so I am really just building on the thread here. I can see though that as you say, those hard to traverse points can certainly be had many times more easily with the kinematic. I don't know what kind of tree cover you have John, but if it is like here, canopy is going to substancially limit your ability to stop and go into places. If you're in SW Oklahoma like Deral is, then kinematic could be very valuable.

I can say kinematic does work. I don't recall any two kinematic points (that reported good stats) not tying at or better than 0.05' to each other (near that 2cm mentioned earlier). So if you are concerned that the technique is a myth, don't. It does work. But you must be mindful of where you can do it.

Shawn

I'm thinking that I might be able to use the Promarks in a sorta psuedo-kinematic method.

I can easily carry a bipod, rod, pin-finder, small shovel, nails and ribbon on a 50 acres survey.

With this in mind . . .

If I were to set a base up(fresh batteries). Then "rove" with the other unit(without initialization), walking through trees, brush, what-have-you with the "rover" off.

THEN . . .

Set the "rover"(it's on now) in an opening while looking for pins while the unit is cooking(20-30 minutes, maybe more), THEN after finding the pin moving the "rover" to either locate the pin(with a 10-15 second occupation), or set a couple of other traverse points using the kinematic aspect which I could use to attempt averaging out inherent errors, so I can return at a later date, go directly to the points and traverse in.

Seems to me it should work using the "no initialization bar" option in the software.

A person could actually walk a large job once with the GPS, static(initialize) into the area, then kinematic more points in the area. THEN onto the next.

THEN return with a TOTAL STATION, rewalk the site and use the static(initialized) points and the kinematic points for traversing

THEN leave to the next, and the next.

I wonder if this is feasable if I were to end up, say about 2000'-3000' from the base?

You could possibly just do short static at that 2-3000' baseline length. By short I mean less than 10 minutes. It would work but you would lack the redundancy that would give you that warm fuzzy feeling.

Shawn

I wonder if a less than 10 minutes initialization would also need rover time?

Kinda the on-the-fly initialization?

Just beware of the l1 kinematic , you have to have open sky no trees or your wasting your time. The locus or promarks are a great solution for setting static control, I have three and use them all the time for control. If you are getting them to do kinematic for get it unless you live in the desert.One tree can ruin lock and yes time to reintialize on a known point or static a new point and reintialize. I have tried contless times to use the kinematic feature and yes it works but was a waste time for the most part and a waste of about 800.0 dollars on the kit. But the way anybody want to buy a kinematic kit for locus....
If your looking at kinematic go L2. My .02

D,

Are you using solutions 2.6? I felt the same way for almost a year. Then I upgraded to ver 2.6 now kinematic on the pm2 works. The money I spent I have made back on one topo job.

But... I felt the same as you trying to get 2.5 to work.

CURT
what does version 2.6 do for you that 2.5 does not do. I did not even know 2.6 was out .