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Localization vs site calibration
What is the difference between a localization and site calibration? Are they the same thing just Topcon calls it localization and Trimble calls it site calibration?
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122 Replies
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In general yes. But I was thrown for a loop and heard of people saying Localize and had to ask some questions and what they were referring to was scaling grid state plane to ground. So make sure you ask the correct questions. But site calibration and localization is just a different term most of the time for getting gps data to fit assumed coordinates data in general.
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Yes, I find it interesting how much terminology gets interchanged when it comes to things such as scale factor or combined scale factor. Makes it confusing.
I am most familiar with Trimble and their terminology so I kinda threw me for a loop being called localization but it looked the same process as a site calibration.
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They are both processes devised to cause field technicians to chase their tails every other day.
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Calibration is a legacy process from the early days of GPS RTK to allow the user to “get on” existing control (it can be done and is better done using static numbers, but I don’t know anyone that does it that way). Calibration was mostly useful to get on local elevation control before Geoid models were better defined. Today with Geoid 18 I don’t see anything useful about it, except it’s a button pushing routine that’s “quicker” than the alternative of using a geometric projection without the “transformations” that are needed to make a Calibration work.
I’m not sure what localization means, if it’s the same process as calibration it doesn’t have any place in our work flow. Possibly it means setting up on a remote point, tying into a known control monument and shifting over the resulting coordinate to the control point system without any transformations. I do that sometimes when control points aren’t secure and that’s a very good way to get a base point out of harm’s way and at a secure location.
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Calibration is a legacy process from the early days of GPS RTK to allow the user to “get on” existing control (it can be done and is better done using static numbers, but I don’t know anyone that does it that way).
Calibrations are done and they do have a place currently and will continue to have a place. When site control already exists and you are now asked to work on the project. You can calibrate to the site control. Sometimes you do not have the parameters that were used to create the site control and must calibrate. Other times a calibration and its inherent error is sufficient for the data you need to collect.
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A surveyor that understands construction staking and knows that construction projects are local in character.
The project control points given in the plans physically represent what the design was based on. They are shown as project control for a reason. A calibration/localization works to verify the project control and ensures that you??ll agree with what??s on the ground. When every construction surveyor and company has a complete understanding of datums and projections maybe Trimble and Topcon will stop supporting calibrations and localizations.
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The horizontal scaling part of a localibration can and should be done without any field work. This eliminates incorrect scaling that can be and often is introduced to localibrations due to bias in existing control or poor decisions. Same issue with a greater chance for bad results in vertical localibrations. Do you have to observe local control and benchmarks? Of course. Even if you have preprogrammed parameters. After you have solid geodetic results on the control and benchmarks develop a projection to fit the results which of course is what a localibration is. It just gives the professional more control over the decision making going into the design.
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If a control network has internal consistency and the elevations were accurately determined, then a calibration is not necessary. An LDP can be applied to the coordinates to put that network on a geometric projection. It takes more office time but will pay huge dividends. 10,000 x 10,000 point, whatever, calculate an LDP to cover the area, if an LDP won’t work then the control is FUBARED anyway.
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What Norm said
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Is there a way to do 3rd party checks without calibrating to the site control? ????
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I think there is a reason that both Trimble and Topcon have field software targeted at the construction surveying market. When that market decides that field localizations are no longer desirable they will respond to the market. I don??t need to be convinced, the market for construction surveying equipment does.
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“Back in the early days…” “Calibration” was Trimble’s term and “Localization” was Topcon’s term for exactly the same thing. Both processes were invented by the GPS manufacturers to sell new-fangled equipment to surveyors who didn’t understand (or never had the desire or opportunity to understand) Geodesy. Some manufacturers (Novatel) were honest about the process and recommended defining the coordinate system in advance whenever possible. Once you’ve designed the system you want to work in, set up, check, check, check and you’re good to go. No need to bastardize your data with calibrations, rotations and scale factors. Math works. Translate instead.
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Is there a way to do 3rd party checks without calibrating to the site control? ????
Of course.
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@fairbanksls I agree the construction market uses gps as much or more than surveyors. The problem is not them. The simple set up there base thats semi permanent for the duration of the job the have to build. They simply calibrate to Surveyors control AKA project Control. I hate to say it but we as Surveyors have created the problem not the contractor or even engineers. We could all simply give our data to engineers with meta data. That could be true state plane or a LDP. Here is the boundary here is the control and our topo and mapping data and here is everything they need. The meta data. They design off of that we a layout or as built what contractor needs or builds. But as soon as you mention grid many of our fellow surveyors cringe and say just set two points and traverse on ground. It creates more work mixing stuff. And when if we had started all data types on same datum correctly it would be much better. Just sent data to a guy and he said your data is wrong. I said what. He said its all shifted. I said ok what datum are you on. He said we used scaled gps coordinates. I said as I took a deep breath as i knew i was in for the long haul. Anyway my data was correct and they had scaled in cad and rotated from some older years of data that was based off a image for a starting coordinates and everything else was traverse at ground. Thats how they got on state plane. Google freaking earth. They were relative to themselves. But rotated and shifted and scaled. From my data which hit a couple ngs monuments fairly well.
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Seems weird that they would say localization vs “scaled” or even scaled to ground is the same number of syllables so it’s not saving words.
I used a sokkia GPS early on as well as Trimble, so I already knew (maybe I initially assumed) they were the same. I’ve heard both terms used interchangeably though the localization term went away after nobody used the sokkia in a while.
Comes back to the recent discussion about all the different terminology used.
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Anyway my data was correct and they had scaled in cad and rotated from some older years of data that was based off a image for a starting coordinates and everything else was traverse at ground. Thats how they got on state plane. Google freaking earth.
Don??t you just love it everyone wants to do everything from the office and google earth these days. Then the field guy has to figure out what happened and ??field fix? stuff. Sadly that happens quite often.
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@350rocketmike Yeah well I almost messed up a lot of data because of word play. They kept saying localize project details are here in this folder please check. I kept asking and asking and they said you don??t know what localize means. I said sure its the same as site calibration. I learned what they meant after asking what steps do you go through describe what you are doing that they were referring to grid to ground was all. It is a term the DOT in a state uses. So as we all are guilty they assumed everyone used that the same way. I have worked literally all over in some capacity of USA and globally I had even worked in that state before and never heard it used that way. A few DOT I know of for projects use a Combined Factor at 0,O to scale grid to ground on the coordinates. So a lot of surveyors that have done dot work use that method all the time because the dot sais that so it must be right. Even here in the dot manual it has scale factor for each county listed the problem is even on that page it states do not use except for specific projects and such. So it truly is not the wisest to use that method in my opinion. I see all the time people using combined factor from opus position results for the whole project and at a different lat long position etc. even seen them not take the inverse and go the wrong direction. Grid ground vs ground grid. I truly think that our simple use of the term grid ground is what created more harm than good. We should have stated reducing ground distances to ellipsoid and projectecting those to grid distances . Because thats what the historical work flow was. Run traverse on ground. Bring that data in and work through all the steps correction to the vertical reduction of slope distance to horizontal reduce ground hz distance to mean sea level/or ellipsoid distances. Then project ellipsoid distance to grid distances then compute the coordinates. At least that is the workflow roughly we used on all the government forms all long hand. Of course we were on UTM and WGS84 and also mgrs etc.
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@on_point well very true in some situations for sure. The biggest thing I see is and it is a catch 22. That is very smart people are taught a procedure this happens on field and office side and 90% of the time it is fool proof. For example cad tech A is taught how to import raw rtk data check for rod height bust rms values etc etc. then choose a point in middle of site and do a one point grid to ground factor. Cad tech A does that for years and cad tech B gets hired and taught the same by the time cad tech C is doing it no one ever truly knows what is going on or the math or how to look around the site before data goes back out to see if that one point is even close to the average ellipsoid height of the project. Now like i said depending where one is that will work. It is a production mentality that vendors created. The one thing that i wish they would have installed in that code writing was force the coordinates to either add or subtract the false northing and easting so they no longer looked like state plane. It??s an option but most offices i have been around do not do that last step. The other is on field side same thing right do it right in data collector from a here position grid ground. Then that project is good but field guy drive to different job or comes back to same job creates a new grid ground on another day in different spot or has same scale on different job. Because thats what was communicated to them. The steps the button flow the procedures. Not what it was doing. Take any small site even 5 acres and build a spreadsheet go to all 4 corners from original data and scale from each and one in middle. Then compare all thise coordinates to raw and each other delta north and east. They will all have good relative to each other but the coordinates shift based on that position and scale. The bigger the project and bigger ellipsoid difference and relief vertical makes a difference. When i do and i have had to do this for a few clients that did not own gps so we set them control to traverse from just to meet county requirements. I give them grid and then the also want it scaled. So i give them a small write up of where and what and exactly how i scaled along with all parameters. One because boss wanted just the same way it was done at company which they did and never even saved how it was done . I first learned this by going to a job to topo. It was wide open field that was seperated by a row of trees. So i just grabbed the gps fired it up because they said it was state plane etc. I started checking control and everything was shifted about a half a foot. It took me a few to figure out where they scaled from but luckily they had chosen a point which was a off site monument they cked to. Thank goodness because i was not driving back to office and the office guy said when I called yeah we scaled but i have no idea from where we don??t care . He didn??t even know what the scale was . He said we don??t use gps rtk but to just get close to finding old control and give county coordinates on the property corners. See it now. Then those sudo scaled state plane coordinates are now given to the very GIS people that have nothing but something that sais nad83 state plane zone x. And then the same cad guy and ls will complain about the GIS stands for get it surveyed. So gis gets shifted that plat and another one some other surveyor does from a different position and scale and no meta data to place it correctly and so gis just tries to make it look pretty. And rubber sheeting begins. ????
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Then the field guy has to figure out what happened and ??field fix? stuff. Sadly that happens quite often.
And it burns a LOT of time and money.
It’s become even more a problem since remote work and work-share have gotten more popular. We shift crews and office staff around to keep everyone fed and projects moving forward. Throughput rather than quality work becomes the goal, and as a result PMs don’t have an incentive to spend the time/money on properly preparing field packages and lining out the crews assigned to them.
Assembly-line surveying looks good on its face but has a ton of hidden costs. As soon as the crews figure out they’re getting the short end of the stick, the good ones leave because they have plenty of opportunities, and the poor quality ones stick around.
“…people will come to love their oppression, to adore the technologies that undo their capacities to think.” -Neil Postman -
It makes more sense for sure when you describe it that way.
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