I always try to indicate the what, when, why, where, who, and how of getting the coordinate. NAD83 using certain city's control isn't the same NAD83 you would get coming off NGS control.
Frequently they would be combined. But for highway projects spanning several miles, it was not unusual to see a recorded control diagram that served as the framework for construction staking, and for subsequent surveys across that span as well. Then maybe a separate ROS for a couple of ROW takings on one end of the project, often referencing the survey control diagram recording number.
When projects went to construction, the survey control diagram provided everything needed for the construction surveyors.
Sometimes, the project scope was to recover and re-establish control, then perform a topographic survey of the site. The topo would simply go to the engineers for design, but the Survey Section might want a record of what was found. In those cases, just a survey control diagram that referenced the previous one used as basis of coordinates.
All surveys are required to have a tie to NC-Grid.?ÿ?ÿ
Do you mean for your client specifically or all surveys in general? If for all, this is not true, although it would nice.
No, it's not like using there instead of their. The surveyor stated that his survey is related to a particular coordinate system and he is not related to that particular coordinate system. Is the error so egregious that it cannot be resolved? No. Is it an act of extreme incompetence? Yes. We should expect more from ourselves and our peers. This is not okay.
I agree, Lee. This is not a simple miscommunication, unless the surveyor provided clear metadata stating the coordinates were scaled by some factor from some specific origin. Otherwise, this was an act of negligence.
As long as the metadata is there, I have no issue with it.
There are multiple ways to deal with grid to ground conversions. All of them have overhead. (This is why I am pushing for LDP in Texas for 2022). The one rule that should always apply is the need for metadata.
?ÿJust to be clear - did the local surveyor provide any metadata regarding his coordinate system?
Agreed.
There was a post downthread about clients and downstream customers being able to overlay GIS data. As professionals who are expected to keep up with technology and industry standards, when we refuse to make our products easily accessible to other geospatial professionals we do a disservice to them and to ourselves. In the OP's case it sounds like this was a private project, but in many cases our products are for public consumption in some way - or might become public. This could certainly be the case for landfill data. If it is an ongoing project that might be handed off to someone else down the line then it should be SOP.
Officials make decisions based on geospatial data now more than ever. It doesn't look good when the folks making a presentation for said officials ask the GIS analysts what is taking so long to produce the maps and data analysis, and they reply "It's the blankety-blank data from the blankety-blank licensed surveyors. It's not on any recognized datum and has incorrect metadata. It's going to take a long time to figure it out."
We complain and/or laugh about about "incompetent" GIS techs. We should spend some more time cleaning up our own house.
It didn't help to have duel-frequency receivers, all were subject to dithering.
Once that was turned off autonomous positioning became more accurate.
Prior to 2000 you would have to have RTK if you wished to do most GPS surveying, even rough corner searches were not possible.
weren't carrier-phase measurements and relative positioning, such as surveyors would have used in positioning of control networks prior to 2000, immune to SA degradation?
That is true. But other factors are at work. When SA was a thing,?ÿ GLONASS was not (practically). You were lucky to get 6 or 7 satellites (all GPS) at any given time.?ÿ ?ÿInternal transmitters weren't a thing yet. So setting up RTK took longer.?ÿ ?ÿGet near any obstruction, you'd lose a couple and BAM! Loss of lock. RTK was far trickier in those days. OPUS wasn't a thing. CORS was barely a thing. Heck, most people's internet connection was dial up, if they had one at all.?ÿ
For the record, even with SA, autonomous positions were usually better than 191 feet. We were warned that they could be that far off, but usually they were better than that by half.?ÿ?ÿ
No metadata was provided. Just a coordinate list with the datum.
I did notice red flag in the datum statement.
?ÿ ?ÿ Horizontal datum - NAD83 NY West Ground
Horizontal datum - NAD83 NY West Ground
That is?ÿsomething I guess, but clearly not enough to reproduce.
I did notice red flag in the datum statement.
?ÿ ?ÿ Horizontal datum - NAD83 NY West Ground
Bingo!
If I apply the correct CSF via OPUS, coordinates are still off by several feet. if I divide the northing of rogue datum from the northing of opus, then apply this scale factor to all points. They are in harmony within a few hundreths of a foot.
?ÿ
The reason for accurately reporting coordinates on the specified datum is so that we can accurately communicate with the other professions involved AND IT ISN'T DIFFICULT IN THIS DAY AND AGE.
For example, we have this thing in California called Geotracker. It's for reporting the coordinates and elevations of groundwater monitoring wells (and other things). Land Surveyors report the 3D position, others take samples (what chemicals are in there), others measure depth to water, etc. The data is used to track where the plume is flowing to. If my positions are just randomly off 200 feet and 1000 feet too high it seriously degrades the accuracy of the tool.
okay I get it, maybe some GIS tech fautily rubber sheeted some old data set but that does not relieve me of my obligation to deliver reasonably accurate coordinates.
The rule in NC is that any survey work involving boundaries (where a plat or report of survey is generated) must be tied to NC-Grid if within 2000' of a NCGS benchmark.
I recently spoke with a member of my board of licensure about using CORS stations as the tie instead of the typical concrete and brass disk benchmarks scattered across the state. They said ties to CORS stations are acceptable and maybe even preferred. This makes Grid ties even easier since I generally use NC’s Real Time Network and they provide vector data from the nearest CORS station.
I combine GPS and total station data on every job (unless I can get everything with the GPS) because it saves me time in the long run.
That's exactly right, but that doesn't mean we need to add the complexity of scale factors to our reported positions. The simpler we make things the less chance there is to screw up. We need to break the habit of pretending the earth is flat.
If we do need to pretend the earth is flat there are extremely few clients who care about the precise absolute location of our points. Those that do usually don't hire "land surveyors". They need geodists. Our clients may require precision in relative position, but state plane is not the right tool for that.