Oh, I spotted the lame attempt at humor. I just thought I'd turn it into something genuinely funny, i.e. the thought that there is this secret message board where all the competent RTK surveyors hang out instead of posting here.
Kent, have you ever worked in the PLSS? (That's the Public Land Survey System. Sectionalized land.)
It's what I work in, almost exclusively.
Nate
Nate The Surveyor, post: 383479, member: 291 wrote: (That's the Public Land Survey System. Sectionalized land.)
It's what I work in, almost exclusively.
My congratulations to you. Does this mean that you don't ever have to worry about survey accuracy?
Myself, I prefer fluorescent orange flagging, with those little Texases on it. I know, I know - APWA specs pink, but dag nab it, I like orange.
2xcntr, post: 383434, member: 584 wrote: "I don't have it in me to argue with your irrational opinions about RTK for surveying."
Really?? Then why would you even start this thread?
Less Filling? Tastes Great?
There were comments made in the metal locator thread that I found to be questionable. I thought it better to discuss those topics in a new thread. I don't see how this is a "less filling, tastes great" conversation. I've provided recent first hand experience, technical information and I've expressed that imaginative surveyors will find the most efficient way to produce measurements that exceed minimum standards. I don't recall stating that one technology is superior to the other and have in fact said that surveyors typically don't care what technology or instrument is the "best", only what efficiently produces measurements that meet a minimum standard required for their project.
I suppose some will assume I was trolling for some argument with Kent. I was not. There is a technology waiting to be exploited, but it requires some changes to current thinking within our noble profession. The most successful users will need to be sophisticated, having a passion and hunger for deeper knowledge and understanding of physical sciences (particularly geodesy). These successful users should also be willing, in my opinion, to reinvest some of the substantial time savings brought by this technology back into their procedures to improve the quality of their work and avoid the egregious mistakes documented by volumes of anecdotal evidence. There exists some misunderstanding about this technology, its capabilities and limitations. Some of these things are moving targets, so a continual discourse is healthy. Some of the misunderstanding seems to be intentional. I don't have the ability to successfully counter willful ignorance, as the root cause is not information, but some other motivation.
I provided two of my most recent projects as examples. I picked these because I wanted to express that I am not cherry picking anything. The industrial site was, by necessity, performed using a blend of RTK and total station. Again, no "less filling, tastes great" here. The job required a blending of the two. How well did the conventional and RTK agree? I provided the real world results for all to see.
Shawn Billings, post: 383572, member: 6521 wrote: There is a technology waiting to be exploited, but it requires some changes to current thinking within our noble profession.
Yes, that is RTK in a nutshell. Until RTK users are able to maintain anything resembling the sort of professional standards that are possible by other means, it's obvious main reason for adoption is that it is fast and part of the mad rush toward quickie-dickie everything. The Locate-a-Ping tip will be perfect for that.
What your fellow East Texas surveyor insisted in the earlier thread was that the appeal of RTK was not that it was fast but that it was the most accurate means of surveying. That was and is obviously ridiculous and richly merits correction, even if you are unwilling to provide it.
Shawn Billings, post: 383572, member: 6521 wrote: There were comments made in the metal locator thread that I found to be questionable. I thought it better to discuss those topics in a new thread. I don't see how this is a "less filling, tastes great" conversation. I've provided recent first hand experience, technical information and I've expressed that imaginative surveyors will find the most efficient way to produce measurements that exceed minimum standards. I don't recall stating that one technology is superior to the other and have in fact said that surveyors typically don't care what technology or instrument is the "best", only what efficiently produces measurements that meet a minimum standard required for their project.
I suppose some will assume I was trolling for some argument with Kent. I was not. There is a technology waiting to be exploited, but it requires some changes to current thinking within our noble profession. The most successful users will need to be sophisticated, having a passion and hunger for deeper knowledge and understanding of physical sciences (particularly geodesy). These successful users should also be willing, in my opinion, to reinvest some of the substantial time savings brought by this technology back into their procedures to improve the quality of their work and avoid the egregious mistakes documented by volumes of anecdotal evidence. There exists some misunderstanding about this technology, its capabilities and limitations. Some of these things are moving targets, so a continual discourse is healthy. Some of the misunderstanding seems to be intentional. I don't have the ability to successfully counter willful ignorance, as the root cause is not information, but some other motivation.
I provided two of my most recent projects as examples. I picked these because I wanted to express that I am not cherry picking anything. The industrial site was, by necessity, performed using a blend of RTK and total station. Again, no "less filling, tastes great" here. The job required a blending of the two. How well did the conventional and RTK agree? I provided the real world results for all to see.
Comparing and checking the results of RTK against conventional is a must for a surveyor to be comfortable with his equipment. I can't imagine anyone who uses RTK that doesn't.
The improvements regarding accuracy and more important reliability have made RTK a better tool than even a few years ago.
The R10/S6 combination is difficult to improve upon.
And remember base/rover RTK is the same thing as base/rover static, it's processing real time instead of waiting for the results.
MightyMoe, post: 383581, member: 700 wrote: Comparing and checking the results of RTK against conventional is a must for a surveyor to be comfortable with his equipment. I can't imagine anyone who uses RTK that doesn't.
The important difference, though, is in how the uncertainty of RTK and conventional measurements are handled. At the crudest level, a surveyor can measure an EDM range between two points located by RTK and say either "checked good" or "need to do this again". At the professional level, a surveyor is able to characterize the uncertainty between the RTK-derived positions, characterize the uncertainty in the EDM range and zenith angle used to reduce it, and both make a meaningful statement about whether the uncertainties were realistic as well as to derive new positions that are more consistent with both types of measurements (together with the uncertainty of the newly adjusted position).
This problem is no different than how one combines any other GNSS-derived position with other categories of measurements.
Kent McMillan, post: 383579, member: 3 wrote: Yes, that is RTK in a nutshell. Until RTK users are able to maintain anything resembling the sort of professional standards that are possible by other means, it's obvious main reason for adoption is that it is fast and part of the mad rush toward quickie-dickie everything. The Locate-a-Ping tip will be perfect for that.
What your fellow East Texas surveyor insisted in the earlier thread was that the appeal of RTK was not that it was fast but that it was the most accurate means of surveying. That was and is obviously ridiculous and richly merits correction, even if you are unwilling to provide it.
Tragically, rather than approach the need for new perspective directly, some have dismissed RTK entirely. We don't typically survey in a controlled laboratory setting. There are instances that I find RTK to be more accurate of available technologies compared to others. Traversing through a marsh with conventional equipment compared to RTK would be one example. Two weeks ago, I staked the West line of a 36 acre tract that was surveyed in the late 1990's. The tract was about 500 feet wide and 3000 feet North to South. In 30 minutes, I tied in three of the four corners that the owner pointed out to me. I found the fourth in short order. My RTK work agreed with the 1990's survey within 1-1.5cm all around. Which was more accurate? Was the original total station survey more accurate? Was the RTK survey more accurate? Who can say? Who cares? I'm thankful for the hard work the original surveyor did in partitioning this tract to such exacting standards, particularly considering the terrain. I'm also thankful that I didn't need to traverse through the slough that bisected the West line to stake the line. I was able to carefully use RTK to locate the line my client needed in a matter of hours. There are instances in which I know RTK isn't the most precise means of performing a survey, however, in many of these circumstances, the difference in accuracy is irrelevant to the project needs.
Shawn Billings, post: 383572, member: 6521 wrote: The most successful users will need to be sophisticated, having a passion and hunger for deeper knowledge and understanding of physical sciences (particularly geodesy).
I've been through countless GPS training classes over the years, as either a student or a trainer, and most of them started with an explanation of the underlying geodesy and mathematics. Almost inevitably, there are people in the room who have the attitude of "I don't need to know any of this stuff, just show me what buttons to push". It's impossible to fully understand what software like Trimble Access and TBC are doing if you don't have at least a rudimentary understanding of how GPS works.
Lee D, post: 383586, member: 7971 wrote: I've been through countless GPS training classes over the years, as either a student or a trainer, and most of them started with an explanation of the underlying geodesy and mathematics. Almost inevitably, there are people in the room who have the attitude of "I don't need to know any of this stuff, just show me what buttons to push". It's impossible to fully understand what software like Trimble Access and TBC are doing if you don't have at least a rudimentary understanding of how GPS works.
Confession of a GNSS sales person - I have difficulty with potential customers who express a desire for their RTK to work like a total station. "RTK is not a total station" (I typically include an expletive in that statement when I'm in private).
MightyMoe, post: 383581, member: 700 wrote: The improvements regarding accuracy and more important reliability have made RTK a better tool than even a few years ago.
This is an absolutely true statement. This is why I mentioned the different RTK systems I've used in the past and my impressions of them. Early on, I saw RTK work at the 1-2cm accuracy. After working with the Altus and Javad systems and newer Trimble systems (and I'm sure now Leica and Topcon as well) I would generally see total station to RTK agreement in the sub-centimeter range. The technology has absolutely improved. Add in a sophisticated user group and you have a remarkable combination.
Shawn Billings, post: 383585, member: 6521 wrote: Tragically, rather than approach the need for new perspective directly, some have dismissed RTK entirely.
Actually, the problems with RTK use are well known. Since its main appeal is speed, why is it a surprise that it is widely used in quickie-dickie surveying? While you may comfort yourself by suggesting that RTK users should occupy all boundary markers for at least four minutes, it would be dangerous to hold one's breath waiting for that to happen.
We don't typically survey in a controlled laboratory setting.
That is actually not true in the sense that no professional uses his or her equipment in ways that cannot be relied upon to produce results of a certain quality. That applies to all types of surveying work.
There are instances that I find RTK to be more accurate of available technologies compared to others. Traversing through a marsh with conventional equipment compared to RTK would be one example.
So, your idea is that the RTK vectors in a swamp are always going to be more accurate than Static or RapidStatic vectors? Presumably not.
Two weeks ago, I staked the West line of a 36 acre tract that was surveyed in the late 1990's. The tract was about 500 feet wide and 3000 feet North to South. In 30 minutes, I tied in three of the four corners that the owner pointed out to me. I found the fourth in short order. My RTK work agreed with the 1990's survey within 1-1.5cm all around. Which was more accurate?
Obviously without uncertainty estimates for either, there is no way of knowing. One would also guess that the actual differences were much larger, but you rotated one or the other of the coordinate systems for a best fit.
Here is an article I wrote and the results of some test that pertain to this discussion.
Javad TRIUMPH-LS Short Baseline Accuracy and Precision with 1 Hz and 5 Hz Corrections
In a previous article titled JAVAD GNSS 5 Hz ÛÏBeast ModeÛ RTK Base Station Corrections Reduce the Time to Acquire a Fix by 72 Percent, the benefits of RTK base station correction rates greater than 1 Hz were discussed. This article will investigate and compare the accuracy and precision of Javad TRIUMPH-LS RTK positions with a Javad Triumph-2 base station with both 1 Hz and 5 Hz corrections in an open sky environment with a short baseline.
Procedure
A TRIUMPH-LS RTK rover and TRIUMPH-2 base station were set up on tripods in a farm field. The base and the rover were adjusted to be at the same height as checked with a 4 foot level. The horizontal distance between the base and rover was measured with a tape measure to be 2.93Ûª.
A TRIUMPH-2 and TRIUMPH-LS setup on tripods in a farm field as the sun sets in the background
Using the TRIUMPH-LSÛªs field software, J-Field, the TRIUMPH-LS was configured to automatically accept collected points and continuously collect points until manually stopped.
ÛÏHow to Stop?Û configuration screen in J-Field set to collect 10 epochs, Auto Accept points and Auto Re-Start
Six sessions of points were collected, points with 10, 30 and 60 logged epochs with both 1 Hz and 5 Hz corrections rates. The RTK engines were configured to automatically reset after each point was collected.
Results
Analysis
- All points had good horizontal precision and 95.4% of all points (2 standard deviations) fell within 0.027Ûª of the average position in the worst group of ÛÏ1 Hz 10 EpochsÛ.
- The point groups had good horizontal accuracy. The physically measured distance between the base and rover matched the averaged RTK groupsÛª position within 0.014Ûª.
- All points had good vertical precision and 95.4% of all points (2 standard deviations) fell within 0.052Ûª of the average position in the worst groups of ÛÏ1 Hz 60 EpochsÛ and ÛÏ5 Hz 10 EpochsÛ.
- Some bias was noted in the vertical accuracy. The base and rover were set up at the same height. The averaged heights of the groups were 0.013 to 0.041Ûª higher than the base station reference height.
- The vertical precision tended to improve as the number of epochs collected increased. The horizontal precision had marginal improve as the number of epochs collected increased.
- The base station broadcast rate does not appear to have any substantial effect on the precision but allowed points to be collected with less time. With 1 Hz corrections, a point with 60 epochs requires 60 seconds to collect, but with 5 Hz corrections, it only requires 12 seconds to collect.
Conclusion
In an open sky environment with a short baseline, the RTK position precision is only marginally improved as more epochs are collected. Higher RTK broadcast rates made possible with Javad RTK systems allow points to be collected faster.
matt8200, post: 383593, member: 6878 wrote: Conclusion
In an open sky environment with a short baseline, the RTK position precision is only marginally improved as more epochs are collected. Higher RTK broadcast rates made possible with Javad RTK systems allow points to be collected faster.
So, should one assume that RTK should be used over baselines not to exceed 2.93 ft. for best results? It's understood that at very small separations, GNSS performance improves considerable as tropo noise cancels.
This is definitely also true of L1 GPS. One of my clients used L1 GPS to allign a rocket sled test rail and found that sub-millimeter results were consistently possible over such short distances.
Unless one is planning on only surveying no more distant than 100 ft. from the base, it might be a good idea to devise other test methods for RTK performance. The natural one is to set up an array of control points that are surveyed conventionally at uncertainties below 1mm with respect to each other and then locate the array points via RTK methods at different distances from the base. Start with open sky and do the same for an array with common multipath sources.
Kent McMillan, post: 383590, member: 3 wrote: Actually, the problems with RTK use are well known. Since its main appeal is speed, why is it a surprise that it is widely used in quickie-dickie surveying? While you may comfort yourself by suggesting that RTK users should occupy all boundary markers for at least four minutes, it would be dangerous to hold one's breath waiting for that to happen.
Actually, I recommend a minimum of three minutes. Although I have found four minutes to offer some improvement. From time to time I make these posts so that I can spur better procedures by users. These efforts are probably not aided by the noise from the #neverRTK crowd, but I keep tilting at those windmills.
Kent McMillan, post: 383590, member: 3 wrote: That is actually not true in the sense that no professional uses his or her equipment in ways that cannot be relied upon to produce results of a certain quality. That applies to all types of surveying work.
Each project provides unique situations with unique variables that require unique solutions. Not exactly a controlled environment which makes it extremely difficult to arrive at an absolute hypothesis that "RTK is always inferior to _____". The contrary can be shown.
Kent McMillan, post: 383590, member: 3 wrote: So, your idea is that the RTK vectors in a swamp are always going to be more accurate than Static or RapidStatic vectors? Presumably not.
The value in knowing that the RTK system has successfully determined the correct integer ambiguities before the user leaves the swamp should not be discounted. On the other hand, a post processed solution may or may not be successful once the user processes the data. (Schrodinger's Cat?) At least until the data is processed, the RTK position that the user has in real time is infinitely more accurate than the post processed result he may or may not have at some future time.
Shawn Billings, post: 383596, member: 6521 wrote: Each project provides unique situations with unique variables that require unique solutions. Not exactly a controlled environment which makes it extremely difficult to arrive at an absolute hypothesis that "RTK is always inferior to _____". The contrary can be shown.
All it will take is some demonstration of a surveying situation where RTK-derived positions cannot be more accurately obtained by other methods. Otherwise, it stands as obviously true that other surveying methods can always produce more accurate results than can be obtained via RTK.
As for the notion that every positioning problem on every survey is strictly one of a kind, that flies in the face of experience. It probably would be possible to describe a typology that covers virtually all of them, sight unseen.
The value in knowing that the RTK system has successfully determined the correct integer ambiguities before the user leaves the swamp should not be discounted.
Basically, you're simply agreeing that RTK is used because it's faster, not more accurate. Accuracy was the point of contention, not speed.
Kent McMillan, post: 383415, member: 3 wrote: I must have missed that post. The point of contention was that one RTK user claimed that RTK is more accurate than other positioning techniques used by surveyors, which is obviously false, as was demonstrated.
Cite Needed. Provide the proof for that statement.
Kent McMillan, post: 383599, member: 3 wrote: Accuracy was the point of contention, not speed.
You may have imported that contention into my thread, but that was not the original intention of this discussion. I've been maintaining that RTK exceeds the minimum standards for many cadastral surveying needs and can do so in many instances with more efficiency than other technologies. This efficiency can have a two-fold impact on surveyors: increased profits and improved services/products. The increase in profits occurs in time savings (provided the surveyor charges appropriately). The improvement to services and products occurs when the surveyor reinvests those time savings into his data gathering procedures, for example adding redundancy to points collected and in locating more remote physical evidence than may be practical with other technologies.
Kris Morgan, post: 383601, member: 29 wrote: Cite Needed. Provide the proof for that statement.
Easy enough.
An East Texas surveyor noted that I had posted:
Well, isn't it a given that if you're using RTK you ARE sacrificing accuracy for speed?
And disagreed with the obvious statement about RTK accuracy by stating:
No. This is not a given and is only the words of someone who has yet to test the equipment for themselves.
What other conclusion may be drawn from the East Texas surveyor's statement but that his opinion is that RTK does not represent a sacrifice in survey accuracy compared to other methods that may take more time?
