It tried something completely new today and it sort of blew up in my face. I wanted to use my 3 ProMark2 units to establish control on a job. I had pre-calculated the job using an artificial coordinate system (20,000/20,000). When I tried to process the files in Ashtech Solutions using the artificial grid, the two points I wanted to hold as my horizontal control held nicely. The third flew off into space. What did I do wrong?

Point 4: Southeasterly property corner: N: 19847.558 / E: 20517.722 / EL (Ground): 1426.74
Point 3: Southeasterly property corner: N: 19694.608 / E: 20077.368 / EL (Ground): unknown.
Point 7: Control Point: N: unknown / E: unknown / EL (Ground): unknown.

Bearing from 4 to 3: N70°50'46"E / Horizontal Distance: 466.16’

There is a large hill between 4 and 3. I had control established on the east side of the job and got to work while leaving the PM2 units to collect away. When I tried to process the data creating a local grid system based on estimate shifts from 4 and 3, the unknown point, 7, did not move into this new system.

I tried re-doing the file a few times following the help file, but to no avail. I ended up processing the file in SPC CA-83 Zone 6. Imported the coordinates into MicroSurvey and translated and rotate and scaled to my local grid system. This worked like a champ and I was able to get on with the job.

So, what did I do wrong? What should I have done? Does anyone else do this sort of thing on a regular basis? Is Mike Margolis or Mike Moe reading this? Can you offer any suggestions? If you want the collected files, let me know, I’ll email them post haste.

TIA

Ian Wilson, LS CA

Ian,
it sounds like you are not processing "all" the points in Ashtech Solutions. Obviously you are holding points 3 and 4 as fixed at those coordinates. 3 for Horiz and Vertical, and Point 4 fixing only Horiz. Were there any other points which did not process correctly? or was it just point #7? Why don't you go ahead and email me the collected files...I'd like to take a shot at it.

Mike Moe

Will do. Mike, as soon as I move them over from the field laptop, I'll email them to you.

Thanks for the quick assist!

Ashtech sure ain't "Big Yeller" in terms of support and assistance! Ashtech, dealers and tech service ,actually listen and respond!

Does your accounting department know about this or have you tied them up and thrown them in the closet?


Modified By D. Ian Wilson on 11/17/2003 at 8:24 PM

Whatever it takes.

I can bet you did one of two things wrong...

1. You left it in state plane and went to control sites tab and changes your 5 millions whatever state plane numbers to 20,000 etc... or

2. you didn't adjust.

Don't use Grid coordinates, go to Project Settings, Coordiate System, choose Ground, tell it your origin point and ground X and Y, then orient to another point, north or an angle. Then adjust and your life will be happy again!

Sorry for the delay, I was playing with RTK in the snow all day today.

You got snow already?

in the People's Republic of Vermont.
Modified By Mike Margolis_ on 11/17/2003 at 10:17 PM

Go back over your original post and clarify a few things for those of us that are playing along.
I've got site IDs of 7701, 7702 and 7703. These are ? with relation to 2,3 and 4? Sure you don't have this pup out 180 degrees? Sent ya mail.
Dave

Process using latitude and longitude then make your first adjustment using state plane coordinates. Hold only one point fixed for horizontal and vertical position.

Create a local grid using at least two and preferably four points that make a box around your project. When you calculate the local grid make sure it sort of makes sense.

Go to the control sites tab and set all of the points you used to define the local grid as control points. Only hold one of them fixed as you make another adjustment of the data. Go to the Control Tie tab in the workbook and look at your closing errors. Decide whether they are something you can live with. Print the page showing your closing errors. Print a coordinate list.

Go back to the control site tab and set additional control sites as you think best considering your closing errors.

When you make your fully constrained adjustment compare your new coordinate list with the one you printed from your minimally constrained adjustment.

Remember that the objective of a fully constrained adjustment is to distribute error and not project error. None of the points should shift more than your closing error. If they do your control is out of balance with the project.

Alternatively use any of the other suggestions that give you the correct results.

Mike, it's supposed to get all the way down to 46°F here tonight.

OOPS! Sorry, Dave… (read in a HAL9000 voice from 2001: A Space Odesy)

7701 as a I in IP PNo 4
7702 as a 60d nail PNo 7
7703 as a 5/8 rebar PNo 3

PNo 4 is the southeasterly property corner. PNo 3 is the southwesterly property corner. The mapped bearing between the two points is the derivation of the bearing N 70°50’46” E (3 to 4)

PNo 7 is the temporary working control point I set at the top of a knoll westerly of the job site. Coordinates in my artificial grid were the object of this exercise.

The convention I use for the site id is the last 2 digits of the job number (2077) followed by the setup. Hence, PNo 4 was the first setup of the day: 7701! I’m open to any suggestions as to a naming convention!

Phil: No, I do not mind another post! Read my next post above then go check the TDS board. You'll see a major difference!

Ian Wilson, LS CA

Ian sent me the files last night and I gave it a go.
Worked things out using his one control point and a free adjustment in Geodetic. Ran those positions (3 and 4) through the NGS program "inverse".

Ians "mapped bearing" between 3 and 4 of N 70-50-46 E differed by the "inverse" solution of N 66-45-17 E, and the distance he has of 466.16' versus 467.13' by multiplying ellipsoidal distance of 142.3816 M by 3.2808333'.....which I realize aint gonna give you a ground distance, but I'ver never seen it more than a couple perhaps few hundredths of a foot different in my area. But then I am at an elevation with minimal ellipsoidal height--- +/- 20 meters or so here in MS.
I'm curious as to how he determined to hold points 3 and 4 fixed.

Anybody else give it a go?

Edit: Just went back and created a custom "ground" grid for the project. If you select Grid North as the orientation, and process/adjust things, Solutions gives a bearing of N 66-45-19 E and a ground distance of 467.16'. Not too far off from the NGS "inverse".

So "where did he go wrong"? Here is what I am thinking, and ifin I'm wrong, Ian I'll buy a plane ticket just to get back to CA and you can beat me with a 2 meter pole.
Ian states that he "pre calculated" the job. If this is the case, he's got a call for a direction and distance between the pins of N70-50-46E and 466.16 feet. This is how he came up with his assumed coordinates, that he wants to hold fixed. GPS solutions are obtained by resection from the SVs, correct? So it wouldn't matter if the rotation of the call was different from Geodetic North as per "inverse". He could obtain the solution and then rotate things in his favorite cogo package---but after he has actually measured between the points, which he has done with GPS. But now he is trying to "jam" a solution by yet another resection controlled by a deed call. Am I on track here Ian?
Modified By Dave Huff on 11/18/2003 at 7:20 PM

Before anyone gets too far into this, I made a boo-boo! I had the unit setup on what I thought was point number 4. It wasn't. It was on a sideline point.

I found out the hard way this morning. Nothing was fitting and I was beginning to have a minor heart attack as they had already started grading and everything was showing up as being off by about 15 feet.

I apologize for the inconvenience.

I did, however, learn a lot from the posts. I should be able to perform this manouver in future.

Thasnk to all the Ashtechies who took the time to respond! This group has the same kinf of feeling and responsivness as some of the old Sinclair computer users groups did 30 years ago!

Ian Wilson, LS CA

SouthWest can get me from New Orleans to Oakland, round trip for about $185.
You buy my ticket and we swap licks with the 2 meter pole. :0
Dave

I was going to post a reply to that, Dave, but when I read it in print, it sounded a bit off color.

In my defense, I'm nursing a miserable cold and loaded up on Sudafed and alavert and still sweating in the cold weather. On eof the draw backs of being a solo surveyor - you don't get to call in sick.

The main thing is that something was learned from it. We all learn something every day.... thank god!
And we learn from our mistakes.....which makes one helluvan education for some of us!

Mike

...(sure hope no one looks up my history on here).

Shawn

We learn by our mistakes. Like my comment the other day on the main board when I found out some software wasn't going to work with my OS.

You live, you learn, and sometimes you wind up with something incompatible.

Good line on tonights Frazier. As Lillith hands Frazier a drink she asks him "what would you say to a drink?"---Frazier replies "Don't get too comfortable in that glass!"

I like that one.

Embarrassed?! OK, I pulled a rookie field boner. Nothing got built from it. It proved up the previous work I'd done. The client was impressed that, even when I was sure I knew what the problem was, I still made a couple of field checks to prove it.

AND---

Look at all the good folks who posted some unbelievable suggestions. Not from the book, but from real life experience.

Embarrased? Hell, I just got a graduate level seminar in geodetic transformations between lat/lon and local artificial grids!

Ian Wilson, LS CA - Ashtechie
Modified By D. Ian Wilson on 11/19/2003 at 9:16 AM

Ashtechie,

Welcome Home

Shawn

Ashtechie or Thalephile. I kinda like the former. Great that you got it to work out Ian. Nothing like the first time you get to check your measurements with 2 totally different methods and they check out good. That's how you get the warm and fuzzies.