Passive Benchmarks

Steve Douty

Steve Douty

Well-Known Member
We have several projects and areas that we return to often. We want our measurements to agree over time and therefore we set passive benchmarks (horizontal and vertical) and return to these marks for project and regional control. We would like to make the passive mark data as precise and accurate as practical. We have several JAVAD units (T-2’s, LS, LS+’s, T-3) along with Jetpacks and radios.

In order to accomplish our goal, we are considering taking a few days and establishing a network of passive marks. The purpose of this thread is to invite discussion from everyone who has an opinion or opinions about how to accomplish our mission.

We have discussed OPAS Projects (without enthusiasm), what action profile(s) to use, (length, number, frequency and method of occupation), adjustments, and etc…..

Please hold forth with your thoughts and opinions and wildest dreams. I am looking for answers, thoughts and opinions that cover everything we could and should think about.
 
Jim Frame

Jim Frame

Well-Known Member
We want our measurements to agree over time
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If you're in a stable area, this is easy to do. If you're in a tectonically-active area, it requires a little more work.

We have discussed OPAS Projects (without enthusiasm)
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Not sure why you don't want to use OPUS Projects, but I find it very useful for establishing reliable control. I use it on just about every job I do that doesn't require a more rigorous standard.

If you don't need to meet any published standards, you have a lot of leeway in your approach. But there's a lot to be said for following guidelines like those addressed in NOAA NGS-58 and -59 when it comes to control. Doing so is sort of the technical equivalent of "nobody ever got fired for buying IBM."
 
Steve Douty

Steve Douty

Well-Known Member
Bryan Enfinger said:
Invest in Justin or Justin 3 software, very robust and professional package for analysis of GNSS data and adjustment.
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I have watched the video and looked at the website sales information. Not real sure what it really does or how to train on it. I will continue to explore this option.
 
Steve Douty

Steve Douty

Well-Known Member
Jim Frame said:
If you're in a stable area, this is easy to do. If you're in a tectonically-active area, it requires a little more work.


Not sure why you don't want to use OPUS Projects, but I find it very useful for establishing reliable control. I use it on just about every job I do that doesn't require a more rigorous standard.

If you don't need to meet any published standards, you have a lot of leeway in your approach. But there's a lot to be said for following guidelines like those addressed in NOAA NGS-58 and -59 when it comes to control. Doing so is sort of the technical equivalent of "nobody ever got fired for buying IBM."
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I thought OPUS projects only used GPS, not GNSS?
 
Bryan Enfinger

Bryan Enfinger

Active Member
The description of the software for Justin and Justin 3 is self explanatory.

I find that the software is very refreshing compared to other post processing software. You use Javad equipment, why not use Javad software.
 
Nate The Surveyor

Nate The Surveyor

Well-Known Member
Just a thought. If you are going to make 10 or 20 bench marks, and quit, perhaps it would serve you well to farm out this part. But, if it's "ongoing" then buy the software, and maintain control of all of it, and learn the software.
Also, how close are your nearest cors stations?
Also, can you live with a tenth of error?
When you go high accuracy, lots of things become important.
But, the number one item on my list would be: carefully adjust your tribrachs, and poles. Maybe even set up a JIG that can be used on your vehicle.
Unless of course, the stations are on metal pipes, and concrete....
N
 
Jim Frame

Jim Frame

Well-Known Member
I guess I'm spoiled, with 2 NGS CORS within 12 km of my office.

But it begs the question: with an iono-free GPS solution available, is there any material improvement to be gained from additional constellation data?
 
Alexey Razumovsky

Alexey Razumovsky

Well-Known Member
JAVAD GNSS
5PLS
Jim Frame said:
But it begs the question: with an iono-free GPS solution available, is there any material improvement to be gained from additional constellation data?
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1. No significant benefit in open.
2. GLONASS was extremely helpful to get fixing in the woods.
3. Galileo, Beidou and even QZSS move fixing to new level in extreme canopy - time to first fix, fixes validation, accuracy and so on/
 
Jim Frame

Jim Frame

Well-Known Member
Back to Steve's original post, if he's creating a durable control network he's going to make sure the stations are in the open, so I again wonder why he's rejecting OPUS Projects as an approach. It does require a minimum of 2 hours observation time for each session, but a control network isn't a place to cut corners.
 
Steve Douty

Steve Douty

Well-Known Member
Jim Frame said:
Back to Steve's original post, if he's creating a durable control network he's going to make sure the stations are in the open, so I again wonder why he's rejecting OPUS Projects as an approach. It does require a minimum of 2 hours observation time for each session, but a control network isn't a place to cut corners.
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We haven't rejected Projects, just not enthusiastic about the time for training and learning. (Lazy!) Also don't necessarily need high order network.

As much as adjustment I am looking for opinions about lengths of occupation and how many times to re-occupy (redundancy). This is going to be a project that I will use as an excuse to ride around over several weekends rather than accomplish something at the house.

Our major concern is to have passive marks that we can return to often with some degree of confidence. (Yes, we are aware that bulldozers and other forces of nature mean that nothing is forever.)

We can set out a base and four rovers at one time. We are considering setting these five units out for a four hour session; then moving at least three of them for another session. Several sessions with different configurations and on different days. Then DPOS at least two days after each session, CORS process on all points. Then compare the results (RTK v. COORS) and average the results in an intuitively weighted (SWAG) manner.

Our present network of marks (about 12 stations over 900 square miles) has evolved over about 20 years and is starting to show the results of different epochs, surface creep, canopy and urban encroachment along with other signs of deterioration. Our intent is to start over with something that we can check into with consistency and aren't ashamed to share. We are rural boundary surveyors, super high order is not necessary, however consistency of our lies is very critical!
 
Steve Douty

Steve Douty

Well-Known Member
Alexey Razumovsky said:
1. No significant benefit in open.
2. GLONASS was extremely helpful to get fixing in the woods.
3. Galileo, Beidou and even QZSS move fixing to new level in extreme canopy - time to first fix, fixes validation, accuracy and so on/
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Alexya,

Thanks for that. It helps my thought process.
 
Adam

Adam

Well-Known Member
5PLS
Why not go for 12 hour sessions? Seems like not much more work involved with 12 hours compared to 4. Go to the bar and get a DD to take you back to get the quip at the end of the day.
 
Steve Douty

Steve Douty

Well-Known Member
Adam, With 4 hour sessions I can stop at all of the bars in the area, support the local economy and pretend I'm working. Twelve hour sessions in one bar give me a bad repetition!

On a more serous side - when (time of occupation) do you hit the point of diminishing returns?
 
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