I'm new to L1 surveying. Is it possible to use the PM2s to measure points on a job site without constraining to a known station? Can I use them to measure distance and establish coords on an assumed (or at least not tied to NGS control) coord system? Thanks!
Modified By james rader on 12/19/2004 at 11:53 AM

Easily done but you will add a slight PPM error based on the true position versus the autonomous position. Not much and not really any problem for a section breakdown or such.

Just remember to record the autonomous position if you have to do more surveying later at the same project so you don't get bit big time.

Same goes for working in the morning on a point, shutting down for lunch then occupying the same point and continuing.

These two starting positions will not be the same.

A little care is all that is necessary to do quality work with no NSRS tie. Just remember that all your work is only related to itself and not to the next project done the next day somewhere else.

Do not report SPC or Lat/Longs on a plat as they will not be correct. You are not tied to the NSRS.

Deral Paulk, PLS OK

that's what i needed to know. thanks!

AND don't return another ay for more data and expect it to agree.

Eventually something should be tied to something.

If on day one you set up on 4 points, A.S. will use the longest(?) setup as a "seed". That's kinda like a control point.

If you go back the second day and set those same 4 GPS on 4 different points . . . on THAT day, A.S. will again use the longest(?) occupation as the "seed", but the points from day 2 will probably not quite fit(5-10 feet) with the dat from day one.

SO . . . if you go back a second(or third) time, make sure you use at least one common point(from day 1) and actually tell A.S. to use it as control . . . even if you don't have a really accurate coordinate on that point.

Deral says:

"Same goes for working in the morning on a point, shutting down for lunch then occupying the same point and continuing.

These two starting positions will not be the same."

True, they will be mere raw data observations. However, should you give the first observation a site ID of say "XXXX" then any observations after that on the same point you use the same site ID and don't worry about it. Solutions will figure it out.

Then John says:

"If you go back the second day and set those same 4 GPS on 4 different points . . . on THAT day, A.S. will again use the longest(?) occupation as the "seed", but the points from day 2 will probably not quite fit(5-10 feet) with the dat from day one."

Well, had John been thoughtful enough to left click on the bottom of the workbook window and pull it upwards, it would have given him access to the "message window" and had he run the "blunder detection" it would have told him he had no "network connectivity" and he wouldn't be jerking around looking for "6 feet of error".

Dangerous Dave

Modified By Dave Huff on 12/19/2004 at 12:53 PM

I think John said use at least on common point on the second or third day.

That is all that is needed in an autonomous network.

Use the same site id's and they will fit.

Did I miss something?

I think you read too fast Dave...

Deral

;-)
Deral,

Yes, John did clarify that in the last paragraph of his post. However, he was "looking for 6 feet of error" on a past project and perhaps he learned the hard way as most of us do. And even though John did clarify this in that last paragraph it isn't necessary to fix the common point in a repeat observation scenario as a control point. That site ID has been processed. When you make a repeat observation on that site Solutions will take it from there.

I pointed out to Frank Morski about the "message window" in my post last night and was making yet another reference to that.

Dangerous Dave
Modified By Dave Huff on 12/19/2004 at 2:11 PM

You mean to tell me that A.S., after using site #day1-1 of the previous day as the "seed" would know, on the second day that site day2-4 was the same as site day1-1 and make the site day2-4 coordinates equal to day1-1 and then use that as the seed for day 2?

????

Try me one more time.

Dangerous Dave

If you use the same site name, A.S. assumes they are one and the same point. Go figure.

Paul in PA

Okay . . . I guess I forgot that the same name would be used . . . I assumed that each day would have all new designators, but that wouldn't make any sense.

This was an oft repeated sermon to my field crew:

One point on the ground = one SiteID.

One SiteID = one point on the ground.

As Deral might tell you...

_TWO and TWO_ are two different sites even if they are the same deep driven rod.

Yes but what if on the first day you occupy BM01, 0001, 0002 and 0003(BM01=control).

THEN the next day you occupy 0001, 0004, 0005 and 0006.

What happens when you designate 0001 as control now?

In the same project there is no need to designate 0001 as control. Process the vectors. When you make the adjustment it will use BM01 and all of your measurements to determine coordinates for all of the points.

Even if BM01 is NOT occupied the second day too?

Not a problem.

The only problem will come if you do not keep a connection from day to day with a common SiteID. It would be nice to see more than one pathway to all points in the survey but that is not essential to success.

Here is the basic concept. Make a dot plot of the points you want to include in a survey project. Assign a SiteID to each dot.

Draw the shortest lines that connect all the dots. Those are the most important vectors to the success of your project.

It does not matter much what order you measure them. You will get error messages if you try to adjust vectors that are not all connected. Just keep making measurements until everything is connected.

That is not the only way to get adequate results. Alternative methods, like radial survey work, can be used. I harp about procedures a lot but it is the results that matter. Proper procedures will take us on the path to good results.

for what I'm asking

On day 1, I occupy BM01(my control), 0001, 0002 and 0003. I process my work for the day

On day 2 I occupy 0001, 0004, 0005 and 0006, and I do not indicate any point from day 2 as control and proceed to process both day's data

Will point 0001 automatically, properly control the setups for day 2?


You know . . . my first units were ProMark Xcm's and MSTAR, so I might be coming from a different world on this.
Modified By John Francis on 12/20/2004 at 8:20 PM

It's going to be important to you to turn loose of the MStar way of doing things and learn a new approach.

Vector processing is about two receivers. It is not really about the network.

On the second day you would not need to reprocess the data from the first day. You would only need to process the data from the second day.

The results of the vector processing will be adjusted relative to your control when you make the adjustment.

That is when connectivity becomes critical. In order to make the project tie together from one end to the other it needs a dot-to-dot that connects everything together.