OPUS. Why?

GOOD point(s)!

There is nothing that OPUS can do, that you can't do as well (or maybe even better in some cases), IF (big IF) you know what you are doing, AND have a GOOD baseline processor (most are by the way).

Unfortunately, far too many folks don't really understand what OPUS is doing behind the curtain, WHY those things are important, or even HOW to begin to set up a rigorous processing session to begin with. The devil is in the details (ephemeris, CORS coordinate estimates, datums/reference frames, etc.).

Loyal

I think it is just another tool in the box and part of using it is understanding what is happening and why. This is a great place for inexperiencied users to learn about OPUS and the how and why of what it does. With everyone learning new software and the many glitches etc...I like to have other ways to check my data.

Regarding checking your work.

I used to process a lot of data with TGO. I have very little experience with other programs but I believe them to be quite good for the type of work most private surveyors do. TGO used several steps to isolate bad data and let you see where the problems were before you adjusted it. If your data was good you could then isolate individual known control and check your solution against published data. When you consider the built in checks and throw a few of your own in the chances that you screwed something up are next to none. After going through all of that and following good procedures in the field I had 99.9% confidence in that program and the resulting data. I never once was able to find a problem with the data on the ground when the gun was used on any of the control. The measurement on the ground was the last check.

So running your data through another processor for a check is pretty much a waste of time if you do it right the first time.

JMO.

Jim

Interesting question Jim.

My short answer:
I don't need to physically occupy a known control point: just collect some data, upload, and wait for the results.
Do you see some sort of issue with that?

Yes, I suppose I could find the corresponding data from CORS stations to match my time frame and local, download and process... more steps, more work.

It is kinds nice to be able to just plunk a single receiver anywhere I like and get high quality results with all the meta data.

I use OPUS quite a bit. I use it as a blunder check. I use it for seed coordinates when I am just trying to get on the grid for simplicity. Would I use it for super tight control, probably not, but, then again, it is a good check.

I worked for a company that we post-processed GPS data on a regular basis, and used OPUS as a check.

I then worked for a company that we used a VRS, and did very little OPUS and NO post processing.

Now that I am on my own, as a solo surveyor, I post process all my static data, and use OPUS as a check. It helps give me the warm and fuzzies that I am doing something right. Of course, the final check comes when you set the total station up and check between your control points.

As others have said, it is just another tool in the toolbox, and I am thankful that it is there.

I'm missing something here. "I run my own data and then use OPUS to check it." What if OPUS gives a differnt answer? You then rerun your data until it matches OPUS? If so, why waste the time running your own data if you are just going to get it to match whatever OPUS gives? Run the data through OPUS and be done with it. Less time = more profit.

Why not?
I have used OPUS, VRS, and post-processed on my own. For us, OPUS is so convenient...I'd hate for it to "not exist."
Occasionally we even upload data to OPUS while in the field...get good results back in 5 minutes.
It doesn't get much easier than OPUS. Even with VRS, we still use OPUS frequently.

That sounds great. What do you use for a basis of bearing when you throw the TS up?

> That sounds great. What do you use for a basis of bearing when you throw the TS up?

Zero.

Usually I record/collect only measurements, generally I have no need for temporary coordinates on the fly.

For mapping or calculations, it is the same as any other survey.
1. magnetic
2. local mons.
3. local control system
4. other Opus derived locations
5. assumed monument/location

the list is endless

> I see a lot of posts here regarding OPUS. Most are about OPUS being down or I can't get OPUS to accept my data or I got my results back and I processed it myself and I get different results.

The "OPUS down" and "OPUS hates my data" stuff is just part of life with OPUS, and an indication of how popular it is. But for every complaint you see there are thousands of happy OPUS reports being cranked out. OPUS has a certain submission timeline that you have to account for in your workflow. Submit too soon after occupation and all you get is cryptic error messages. "Processed it myself and got different results" is usually datum issues or just noisy data.

> My question is this. Why does anyone use it? If you have GPS equipment you probably have a way to process your data.

Maybe. Over the last few years a lot of people bought one receiver to use with their local RTN, and then maybe started collecting static with that one receiver to use with OPUS.
So why use it? Because it's there, and possibly a little more sure than RTK (Being static) and because in the areas where it works well, it gives a common reference.

Post processing software used to be sold with the receivers. In the last 5 years many vendors are hot to sell network RTK equipment, hopefully with the recurring revenue of a network subscription. The post-processing software is a one-time cost, expensive, rarely mentioned.

> If you don't know how to process your data you should learn.

Weelll, unless you wrote the post-processing software yourself, it's no less of a black box than OPUS as far as the calculations, and it's just professional judgement, using the things you CAN calculate, to decide what to trust and how much.

As far as learning to process your own so you can compare, agreed. The next step for us after RTK-then-OPUS was to learn post-processing from the Topcon Tools demo, which will process 5 stations of dual-frequency. So we started post-processing with CORS or WSRN base station data, comparing those. Lately comparing both of those with WSRN VRS RTK. Next up is to keep learning PAGES-NT, which is free but has a steep learning curve. And back at ya, if you don't know how to use OPUS you should learn.

> Sort of like running a traverse and not being able to check the closure and adjust it if you have to.

Here's where I disagree. Just like your post-processing results, OPUS results have all the "closure" data you need. OPUS gives you an error ellipse, statistics about the number of epochs used, etc. It is up to you to decide, based on that, if the data is "good enough". It is also up to you to check it with an independent method. It will adjust fine in your least squares with your terrestrial measurements, once you have QC'd the data. That's what the error ellipse and covariance matrix stuff are for.

> It's all survey data and surveyors should be able to process their own data. Would you send your terrestial data to NOAA to be processed? probably not.

That's a pretty cool idea! Hmmm ... an online service that processed star*net or .rw5 or .fbk ... If anyone had a service like that to check my terrestrial data, I would surely use it as a doublecheck.

> Many here know that the time and cost to process GPS data is minimal compared to the time it takes to collect the data, especially when you are talking about control data.

One hour of static GPS = 4 hours of processing for me. That's for a lot of OPUSing and base station downloading and re-processing and comparisons. Curious about other people's estimates.

> I really don't even like the idea of OPUS. Too many surveyors or soon to be surveyors using it in place of good, sound procedures and practice.

You could say the same thing about any measurement tool, old or new.

I use it for state plane coordinates... most municipality's require SPC on surveys, OPUS SPC are good enough so that is what they get. It beats hunting NGS Monuments for sure.

Because It Is A Redundant Solution

An OPUS position is 3 independant positions done with a different software than on my computer. Yes I can do it myself, and do do it. I will not accept an OPUS position unless I have my own solution within allowable tolerances. However because I have clients that put more faith in OPUS than me I will often hold 1 OPUS position, and solve from there.

For my own work I hold what I do, and confirm it with OPUS-S or OPUS-RS checks.

I am a professional surveyor and I make professional measurements. OPUS allows me to confirm that my work is good.

If you don't use OPUS, exactly how professional are you?

Paul in PA

Because It Is A Redundant Solution

No kidding, it takes all of 5 minutes to use OPUS, why wouldn't you?

Also you can get the extended report and use the vectors yourself in your adjustment software.

OPUS uses Pages which is optimized for long baselines.

I use OPUS to get an accurate position and check the geoid model against benchmarks.