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Setting up control for construction site
MightyMoe replied 1 year, 4 months ago 18 Members · 43 Replies
@wa-id-surveyor
The benefit of coordinates that don’t look like SPC is in cases when somebody takes true SPC and scales coordinates instead of distances to move from grid to ground. As long as the metadata explains what was done and everyone is careful to understand, it doesn’t matter. But lopping off the high digits of the altered coordinates so they don’t look like SPC can keep someone from misusing them and creating problems.
I understand that age old statement but do not agree with it. Anyone blindly using coordinates as SPC has no business using them. I haven’t had any issues in 15+ years of using data in this way. Also, I have not heard of any State or City projects in my work area having any issues. It might be a regional type thing as well, not sure.
There are a few of the super large firms in our area that are hamstrung by HQ and still have to create projects with odd false northing and eastings.
Back in the day my HP48gx with SMI couldn’t carry enough digits to work with state plane. So you had to truncate the numbers. Later versions of SMI fixed this, but it was a real thing for a time. That is one of the ways these things get started.
@wa-id-surveyor
The benefit of coordinates that don’t look like SPC is in cases when somebody takes true SPC and scales coordinates instead of distances to move from grid to ground. As long as the metadata explains what was done and everyone is careful to understand, it doesn’t matter. But lopping off the high digits of the altered coordinates so they don’t look like SPC can keep someone from misusing them and creating problems.
I understand that age old statement but do not agree with it. Anyone blindly using coordinates as SPC has no business using them. I haven’t had any issues in 15+ years of using data in this way. Also, I have not heard of any State or City projects in my work area having any issues. It might be a regional type thing as well, not sure.
We’ve worked with dozen’s of engineering and surveying firms doing the DOT thing. From design to build no one I’ve ever heard of was confused. Like you say,,,,,maybe a regional thing. The system became much more useful with the advent of CAD. Now it’s so simple to scale in ortho’s, guads, gis, whatever you need and your still “on ground”.
Anyone blindly using coordinates as SPC has no business using them.
From ’97 to ’04 I worked for an outfit that did a lot of large subdivision development. Most commonly the projects would be on a local coordinate system, but some times a scaled to ground from state plane. The work flow would go like this:
1. Control would be established, topo collected, and boundary monuments recovered. Basis of Bearing at this point was either assumed, hand compassed, or, sometimes, state plane.
2. A topo base map would be prepared with planning level boundary resolution and sent upstairs to engineering.
.
.
.
a year, or two, or three passes
.
.
.
3. The project, now designed, comes back downstairs for construction staking. A great many of the wood hubs and PK nails previously set for control have turn to dust so a whole new set of control has to be run, more or less on the old coordinate system, with luck.
4. Staking and construction begins ……control is destroyed and replaced daily, but rarely if ever does any of that get back to the office.
……. now the fun really starts
5. The platting department (one particular guy who specialized in putting the plats together) takes the project coordinate system (the one that came downstairs, sans any of the control recovery and rehabilitation) and rotates it on to some logical basis of bearings – ie/ holding a line of some adjacent earlier plat for which monuments had been found – and produces a exterior boundary record of survey as required by local law, and the plat itself. This usually takes a few months to get approved. When ready, he pumps out a set of coordinates for staking of the boundaries and lots. Those coordinates look just like the “project” coordinates, only they are rotated. They have the same numbers and descriptors. For the most part the control points listed no longer exist. The file names and printouts all carry the same project numbers as the project control.
Believe me, it was a cluster-Fxxk, every dxmx time. Under these conditions we would have welcomed a coordinate shift at a minimum. Granted, there are a lot of other ways this could have been managed – but truncating the coordinates is the one way that this one guy could have taken independent action.
Also, ditch the prism pole for control work
I try to use a peanut prism as much as possible when practical Haha
Anyone blindly using coordinates as SPC has no business using them.
From ’97 to ’04 I worked for an outfit that did a lot of large subdivision development. Most commonly the projects would be on a local coordinate system, but some times a scaled to ground from state plane. The work flow would go like this:
1. Control would be established, topo collected, and boundary monuments recovered. Basis of Bearing at this point was either assumed, hand compassed, or, sometimes, state plane.
2. A topo base map would be prepared with planning level boundary resolution and sent upstairs to engineering.
.
.
.
a year, or two, or three passes
.
.
.
3. The project, now designed, comes back downstairs for construction staking. A great many of the wood hubs and PK nails previously set for control have turn to dust so a whole new set of control has to be run, more or less on the old coordinate system, with luck.
4. Staking and construction begins ……control is destroyed and replaced daily, but rarely if ever does any of that get back to the office.
……. now the fun really starts
5. The platting department (one particular guy who specialized in putting the plats together) takes the project coordinate system (the one that came downstairs, sans any of the control recovery and rehabilitation) and rotates it on to some logical basis of bearings – ie/ holding a line of some adjacent earlier plat for which monuments had been found – and produces a exterior boundary record of survey as required by local law, and the plat itself. This usually takes a few months to get approved. When ready, he pumps out a set of coordinates for staking of the boundaries and lots. Those coordinates look just like the “project” coordinates, only they are rotated. They have the same numbers and descriptors. For the most part the control points listed no longer exist. The file names and printouts all carry the same project numbers as the project control.
Believe me, it was a cluster-Fxxk, every dxmx time. Under these conditions we would have welcomed a coordinate shift at a minimum. Granted, there are a lot of other ways this could have been managed – but truncating the coordinates is the one way that this one guy could have taken independent action.
That’s pathetic and absurd, frankly it wouldn’t matter what system the project started with if they change it in the middle once or multiple times. There’s no fixing that.
Anyone blindly using coordinates as SPC has no business using them.
From ’97 to ’04 I worked for an outfit that did a lot of large subdivision development. Most commonly the projects would be on a local coordinate system, but some times a scaled to ground from state plane. The work flow would go like this:
1. Control would be established, topo collected, and boundary monuments recovered. Basis of Bearing at this point was either assumed, hand compassed, or, sometimes, state plane.
2. A topo base map would be prepared with planning level boundary resolution and sent upstairs to engineering.
.
.
.
a year, or two, or three passes
.
.
.
3. The project, now designed, comes back downstairs for construction staking. A great many of the wood hubs and PK nails previously set for control have turn to dust so a whole new set of control has to be run, more or less on the old coordinate system, with luck.
4. Staking and construction begins ……control is destroyed and replaced daily, but rarely if ever does any of that get back to the office.
……. now the fun really starts
5. The platting department (one particular guy who specialized in putting the plats together) takes the project coordinate system (the one that came downstairs, sans any of the control recovery and rehabilitation) and rotates it on to some logical basis of bearings – ie/ holding a line of some adjacent earlier plat for which monuments had been found – and produces a exterior boundary record of survey as required by local law, and the plat itself. This usually takes a few months to get approved. When ready, he pumps out a set of coordinates for staking of the boundaries and lots. Those coordinates look just like the “project” coordinates, only they are rotated. They have the same numbers and descriptors. For the most part the control points listed no longer exist. The file names and printouts all carry the same project numbers as the project control.
Believe me, it was a cluster-Fxxk, every dxmx time. Under these conditions we would have welcomed a coordinate shift at a minimum. Granted, there are a lot of other ways this could have been managed – but truncating the coordinates is the one way that this one guy could have taken independent action.
That was more or less the same that I??m accustomed to; start with boundary and topo on SPC then later when construction starts we would establish a control line on a local coordinate system. Just made sure anyone doing any layout had the localized job.
I??m starting to think scaled coordinates must be a regional thing. Guess it depends if your in a flat region or the mountains? Also, I couldn??t imagine doing any layout with the gps unless it??s for a house, even then only for clearing or digging footers. Especially since it seems like everyone wants layout in the thousandths anymore. ????
I??m starting to think scaled coordinates must be a regional thing.
In the Pacific Northwest there is just too much tree cover to routinely use GPS. The bulk of survey work is still done with the total station. There are plenty of outfits around here that do not even have GPS. It is convenient with the total station to work, even when state plane has been established, without a projection. So a lot of jobs get scaled to ground. It was, for a long time, the Oregon DOT’s policy to do so.
A while back – over 10 years ago – ODOT came up with the low distortion projection setup, which allows working with a total station, no projection, no scaling, without significant differences. Nevertheless a lot of outfits continue the old practice of scaling state plane to ground, “because that is the way they have always done it”. Grrrrrrrr.
That’s pathetic and absurd, frankly it wouldn’t matter what system the project started with if they change it in the middle once or multiple times. There’s no fixing that.
Oh…it could have been fixed. Easily. It would have involved removing one person at the top of the food chain. One very controlling personality.
Let me just say that when you have a problem in your organization of this nature it is the most talented people who have the greatest mobility, and leave it at that.
@norman-oklahoma smi construction 5 IV or VI was the best roads program ever. It had everything. You could set up on any station and offset etc. and do anything you wanted. But you are correct on the truncation issue early on.
I see a lot of things that work 90% of the time now but that 10% of the time it does not and no one catches it because they are taught processes to follow not how to understand what is going on. Example use TBC find a point in middle of the site and scale spc to ground. Never mind that all coordinates that look like spc are no longer spc except the point they chose. It works 90% of the time its all relative. And only when the site is small and not a lot of elevation change. The engineers love it because they can make exhibits that layover imagery. Problem is when you do the same thing over and over again on a site that is larger and it has more distortion and elevation change. Saw one the other day and it excited way more than the tolerances for control in PPM because of a one point scale. Some don??t understand the elevation factor (aka ellipsoid factor for nad83). I had to show them I could still choose a point horizontal in middle of site but use an average of elevations / ellipsoid heights from around the project and come up with something that was more logical and met the accuracy requirements for the job. I did a lot of reading here and other places on LDP and because of this site. It is logical it can work and still make everyone happy. Now I am not afraid at all to stay on spc or utm i don??t even get scared if it was designed at ground. Its math its not hard the equipment today makes it so easy. To design or layout or survey on a projection. Yes projection have distortion yes tge world is not flat. I mean old timers did it without a hand held computer and we are living in 2022 and surveyors are like well its to complicated and well just do it this way. Thats the way it has always been done. Really because i am not that old and I have done hand comps for ground to grid traverses all over this world let alone USA and I am a dumb redneck from Tge south. If I can anyone can. Why why why do people make it so difficult. Had a LS tell me he can??t get past scaling elevations to meet spc tolerances and the elevation he ran levels on has to change. I almost lost it completely. I said elevation doesn??t change numerical value it was used i. NAD27 and such for elevation factor. To go with scale factor to create combined factor. He still doesn??t get it.
This was my rant Norman. Not at you at all but with you. I just cannot understand how we as a profession have not taken the time to get it. Its a freaking ratio and we can solve it six ways to Sunday. We live on a surface that rotates wobbles expands contracts and gravity is not the same at any given location. So even those who say ground distances only don??t understand the impacts of gravity mass on a ledge traversing around a mountain and up and over it that we have more errors that we have not accounted for versus placing data on a known system that helps prevent issues to the Walmart down the road. And school. Or whatever. I mean most of the math we use is not new it has been around since the Roman empire since pyramids were built aztec nations etc etc. we can keep going back in history. Way before calculators or even slide rules. Now we have more power in a smart phone that fits in our pockets and we have those who say it is to difficult to do. I honestly don??t understand.
I have a unique career. It is like the best i can describe it as a grandparent. Or a parent that had to be away for a while. When we see our kids every day we see little changes. When we go away for months or weeks we see a lot of change and growth because we were not there every day. Thats how I am with surveying. I have always been around in some form but being a way from private sector every day for a while and returning I see so many things that are mind boggling. It as if the technology grew but the mindset has not in some ways. I can only say what I see. I see people that are awesome drafters aka use software know what buttons to push. Same in field side. I see so much potential constrained by this is how we always have done it that a generation has gone by and they can??t explain why just this is what we always have done. I saw it at last company only reason we use gps is to get close to spc so engineering and county can put in gis. Same people say gis is wrong its not accurate. Well i say what is accurate. Whats the truth. Well i see boundaries on imagery not correct by about 3 foot or so. I say how accurate is imagery and you gave them your data saying it is accurate but you scaled your spc and gave it to them. So again what is truth. I say both are right and both are wrong. All imagery is based off some geodetic control. Then you have image resolution. You have projections and mapping scales. Let me say this If Land Surveyor does not take the time to gain understanding in all aspects of measurements and datums and projections it will not be good. Because imagery resolution and its pixel size will only ONLY get better. And it is way better now than most realize. Trust me. You would be blown away. And it’s accuracy can not get better than its source/foundation which is geodesy/ and geodetic control. It all works together. So we must in my country boy way is get better get smarter get more edumacated. Learn the system to make it better. I believe we will always have Land Surveying as long as we are free peoples. And as long as we strive to become better. Think of how far technology has come but also remember our angular accuracy was achieved way before our current technology so as we have lots of powerful gadgets and electronic equipment. The accuracy of that robot or total station angular was achieved in transit days transits that weighed so much they were hauled in special buggies pulled by oxen horses and mules.
I’ve been producing products exclusively in SPCs (at ground) for 15+ years
IF THEY ARE REDUCED TO GROUND MEASUREMENTS THEN THEY ARE NOT STATE PLANE COORINATES BY DEFINITION.
After almost 30 years of working with GPS across the west I can tell you it is a problem. Even if you do a great job of creating a metadata trail the chances of it making it on the engineering plan set is nil. If I come on project with no metadata and coordinates that look like grid values I have no way of retracing your steps to get back in the geodetic world from the quasi-grid system. And when your data makes its way directly or indirectly into someone’s GIS/BIM it will be straight up wrong. If you take the time to truncate the scaled values then everyone is the wiser.
I just finished up with a mile plus long road job that the control was done in this fashion. Of the 14 original control points only the four that are off site are remaining. I had the advantage of knowing, based on the pre-construction record of survey, that only one of the points was actually on grid. Unfortunately the survey did not divulge the scale factor used. The inverse between the quasi-grid coordinates and the grid coordinates was over 0.1 ft just a couple of thousand feet. I spent close to a day recovering the points and collecting GNSS observation to develop ground coordinate system.
I’m not sure what the adversity to truncating is. At one point in time it was nice to be able to overlay imagery that was produced on grid system. Those times are well in the past, now you define your scale and translation in CAD which allows geodetic data sets to be imported seamlessly.
IF THEY ARE REDUCED TO GROUND MEASUREMENTS THEN THEY ARE NOT STATE PLANE COORINATES BY DEFINITION.
I was wondering when someone was going to point this out. Took a little longer than i thought.
Back in the day my HP48gx with SMI couldn’t carry enough digits to work with state plane. So you had to truncate the numbers.
C’mon, man…
Everybody knows if you switched over to metric, and keyed in coordinates that way, it worked just fine.
The old SDR33’s were like that too.
And when you switched back to feet, it displayed the correct values out to 2 decimals.
The accuracy of that robot or total station angular was achieved in transit days transits that weighed so much they were hauled in special buggies pulled by oxen horses and mules.
My Trimble S5 only requires 1 mule to transport it.
Oxen are hard to come by these days, and the mule eats less.
The accuracy of that robot or total station angular was achieved in transit days transits that weighed so much they were hauled in special buggies pulled by oxen horses and mules.
My Trimble S5 only requires 1 mule to transport it.
Oxen are hard to come by these days, and the mule eats less.
I worked with a Trimble S6 and S7 and both of them were heavy especially traversing through the woods.
IF THEY ARE REDUCED TO GROUND MEASUREMENTS THEN THEY ARE NOT STATE PLANE COORINATES BY DEFINITION.
After almost 30 years of working with GPS across the west I can tell you it is a problem. Even if you do a great job of creating a metadata trail the chances of it making it on the engineering plan set is nil. If I come on project with no metadata and coordinates that look like grid values I have no way of retracing your steps to get back in the geodetic world from the quasi-grid system. And when your data makes its way directly or indirectly into someone’s GIS/BIM it will be straight up wrong. If you take the time to truncate the scaled values then everyone is the wiser.
I just finished up with a mile plus long road job that the control was done in this fashion. Of the 14 original control points only the four that are off site are remaining. I had the advantage of knowing, based on the pre-construction record of survey, that only one of the points was actually on grid. Unfortunately the survey did not divulge the scale factor used. The inverse between the quasi-grid coordinates and the grid coordinates was over 0.1 ft just a couple of thousand feet. I spent close to a day recovering the points and collecting GNSS observation to develop ground coordinate system.
I’m not sure what the adversity to truncating is. At one point in time it was nice to be able to overlay imagery that was produced on grid system. Those times are well in the past, now you define your scale and translation in CAD which allows geodetic data sets to be imported seamlessly.
Sorry, had to quote this again for posterity so that future readers would see it twice.
Scaling SPCS grid coordinates (especially from the origin) without truncating (therefore resulting in coordinates that are NOT grid or state plane but look very similar) is poor practice. Even with metadata.
This gets F’d up all the time, by both non-geomatics folks and geomatics folks who should know better. I too have followed alleged “professionals” whose “metadata” were clearly wrong, and could be proven wrong just by plugging some numbers into a calculator.
Although I used to love, and still occasionally use ground-scaled values, I won’t shed a tear if they get left in the dust.
Industry leaders, and the savvy clients too, are already seeing the advantage of working on projections that can be ingested by, and transformed on the fly, by other software packages – rather than screwing with Excel or working up a bogus PRJ file to simulate “ground state plane” (an oxymoron if there ever was one). If state plane doesn’t fit the bill due to distortion, work up another projection. It’s easier and less prone to error or screwups.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman@john-putnam you are correct. I am taking over managing a ongoing project now and Someone assumed it was spc scaled to ground because thats how there surveyors worked so everyone must do the same. On top of that as I read the requirements for the job to get familiar they require spc at a specific epoch and they require a specific vertical datum. Lets just say no one is doing it the way it was dictated out and that was literally a 15 minute read for me as I requested the project requirements info so I could dot my I??s and cross my T??s as i try to get organized for the job. But all this ASSUMING stuff is for the birds. I cannot stand to scale to ground and leave it looking like state plane. One when i am forced to even my csv file is named in a way to raise the red flag. It would be something long but its only way i can get the meta data to follow it. On a plat or engineering drawings is one thing but to different crews from different companies I cannot make assumptions they will know what they are or even where i scaled from. Or how. If i were in charge it would not bother me as i would be able to one either set up the site as a LDP or leave it on true grid or project coordinates system as needed and have that flow.
Use to in TGO i have not done this in TBC as it was not required. But if you did a site calibration or did a scale to ground you could save those parameters as its own unique coordinates system. Then export it a couple different ways to field crews data collectors like a job file only contains the site datum or as a coordinates system let them choose for the library just like any other coordinates system . It is done so much here by so many. Set two points with rtk on spc. Then import them to scale only job and traverse. And every plat sais nad83 grid. Every engineering drawing nad83 grid spc etc etc. some are a little smarter as they will scale to ground on those starting pairs but they all still call it spc grid. No matter how many times i set up spreadsheet in excel showing them how much of a shift in north and east it is around the site or property. If i go out myself and i know 100% i will process the data and reduce it. Rtk robot is all on grid spc. I save reduce adjustments and have a project and csv files all labeled 6 ways to Sunday it is nad83 what epoch etc vertical datum per whatever geoid 18 and or ngs bm etc. then i scale everything down or up to a ground system and truncate. Place all parameters in a folder and in a document that sais read me first before doing anything. Then its all up to whoever. When i have done that they usually make me add back the i truncated northing and easting. Drives me nuts.
This thread is fascinating.
I must say it’s changed my opinion.
Everyone that’s offended by the way DOT uses coordinates should approach them (photos and surveys would be a good start) and explain to them how everything they’ve done for the past 60 years is all wrong.
Tell them that you will not even try to get any work from them as long as they incorrectly survey.
Meanwhile, even though I know it’s all f’d up now, I’ll have everyone’s back and continue to suffer and do these ROW, title, property surveys and investigations for them. All of you can rest assured that you won’t have to suffer like I do.
I will draw the line on one thing. Since they don’t use sacred coordinates like they should, I will not stake the offensive surface coordinates on the ground for any project, no slope stakes, blue tops will be done by me!!!!
Imagine asking a modern surveyor to do that!!!!!
Whatever you do, don’t try and become approved to do this type of work, it’s so beneath you. Sure, money might be flowing like never before for contracts with DOT, so what, don’t succumb to the idea of profitable, stress free, on time payment type of work.
We must protect sacred coordinates above everything else!!!!
The sarcasm force is strong with this one.
Willy
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