@mightymoe "Same here, walk out of the office to the field and the projection is set, it never changes. It's not difficult to figure out what to use."
So if you knew that there was a published mon on grid NAD83 & NAVD88 about 2000' away from the job mentioned above, could you use the SF published with that mon and convert it to ground and then take the rover and check into those coords H&V or is there some other conversion needed ?
@mightymoe "Same here, walk out of the office to the field and the projection is set, it never changes. It's not difficult to figure out what to use."
So if you knew that there was a published mon on grid NAD83 & NAVD88 about 2000' away from the job mentioned above, could you use the SF published with that mon and convert it to ground and then take the rover and check into those coords H&V or is there some other conversion needed ?
The last one I tied into was a HARN point, and I checked into it .02'h,.04'V. Not sure what you're asking, as far as converting I use Lat, Longs for checks horizontally, I don't concern that type of control with grid. Grid is a function, it's not controlling data.
The last one I tied into was a HARN point, and I checked into it .02'h,.04'V. Not sure what you're asking, as far as converting I use Lat, Longs for checks horizontally, I don't concern that type of control with grid. Grid is a function, it's not controlling data.
Our county published control is just NAD83 coords with no lat/long and apparently they think it is controlling and ask us to tie our maps to it so would I have to convert it to lat/long to check in using Trimble? Sorry, I do not use Trimble so this might be a dumb question, can you enter lat/long directly into your DC or what do you do to check a point that has lat/long?
The last one I tied into was a HARN point, and I checked into it .02'h,.04'V. Not sure what you're asking, as far as converting I use Lat, Longs for checks horizontally, I don't concern that type of control with grid. Grid is a function, it's not controlling data.
Our county published control is just NAD83 coords with no lat/long and apparently they think it is controlling and ask us to tie our maps to it so would I have to convert it to lat/long to check in using Trimble? Sorry, I do not use Trimble so this might be a dumb question, can you enter lat/long directly into your DC or what do you do to check a point that has lat/long?
If you have to use existing control monuments you should locate them on your system and show a tie to them, I have no idea how good they would be, NGS old control monuments locally vary from .7' to almost 2' from "real" coordinates. I consider them bad data unless they are HARN control. Then they tend to be within .15'. There are approximately 3 HARN points per county, one every 1500 sq miles or so. No, I don't use NGS monuments for much of anything, I often walk or drive by them and remember using them during my big instrument traverse days. Why would your county use them as control, isn't CORS in the area? If there is; then update the coordinates on these points as you survey them, send that to the county. Maybe you can start good control on them, if they do check then they are way better points than I'm used to.
As far as Lat, Long, you should see that when you enter the grid point, your DC should generate a Lat, Long from the NAD83 coordinate, if it doesn't use the program NCAT, it will give you Lat, Long.
@mightymoe which NAD83. NAD 83 is the lat and longs. That’s the datum. Then you get state plane or UTM or LDP based on that LAT LONG. Yes in Trimble you can key in or have a csv file just like northings and eastings. It will however re-project it to the state plane also. You can see that at any time state plane or lat longs etc. HARN. So on the data sheet NGS which Lat long are you going to if it has been updated adjusted it is nad83(2011). Depending on which state how all of that was adjusted etc. and when over the years. NAD83 (2007). NAD83 CORS 96
@mightymoe which NAD83. NAD 83 is the lat and longs. That’s the datum. Then you get state plane or UTM or LDP based on that LAT LONG. Yes in Trimble you can key in or have a csv file just like northings and eastings. It will however re-project it to the state plane also. You can see that at any time state plane or lat longs etc. HARN. So on the data sheet NGS which Lat long are you going to if it has been updated adjusted it is nad83(2011). Depending on which state how all of that was adjusted etc. and when over the years. NAD83 (2007). NAD83 CORS 96
The HARN point I was checking into has an 83(2011) adjustment shown. It's a CBN. I occupied a point a couple of miles NW of it and drove over, hit it with a RTK shot with the rover. Later after processing my base point to the nearby CORS point, I check the numbers and found it very tight. My base was sitting between two NGS base points. West base and East base that were the basis of the area NAD27 original surveys. Kinda cool, I didn't tie either one.
I wasn't on any state grid or even close to either one (I was just into one state), instead I was on my own projection with the CM running along a longitude that split the section I was in, the grid was set so there was no more than 3ppm between ground and grid at my work area.
which NAD83. NAD 83 is the lat and longs. That’s the datum. Then you get state plane or UTM or LDP based on that LAT LONG.
I see your point, and I'm not saying that you are wrong. But you are not entirely right, either.
The Oregon North and South Zones is defined the same for both NAD27 and NAD83, except for the false northing and easting. The other two states I have first hand knowledge of, Washington and Oklahoma, have similar setups. I'm guessing that most other states are the same. So it is easy to look at a set of northings/eastings in a given area and know right off whether they are NAD83, NAD27, or local. Except in cases where the coordinates have been scaled.
I get the sense Landbutcher might be in a state that requires ties to old NGS monumentation. Hopefully these have been occupied by GPS recently to get the values. If not there isn't anything stopping a surveyor from tying them into the survey and showing a tie from them to a monument onsite, much like section corner ties our subdivisions are required to show. Doesn't mean the NGS monument has any value as geodetic control. I always show a lat, long on my section corner ties and metadata for distances and bearings shown on the survey. Bearings are based on the XXX State Coordinate System NAD1983, East Zone (many states have exact wordage for expressing the coordinate system). Distances are multiplied to surface by the Project Adjustment Factor of 1.000235. I will not state any coordinates and lat, long is given to three decimal places in seconds. If anyone wants state coordinates they can easily compute them. I would treat NGS monuments the same, tie them show my lat, long, show record lat, long, and give metadata for bearings and distances.
So if you knew that there was a published mon on grid NAD83 & NAVD88 about 2000' away from the job mentioned above, could you use the SF published with that mon and convert it to ground and then take the rover and check into those coords H&V or is there some other conversion needed ?
Enter it into TBC on grid, the toggle it back to ground and export those values for a check. We would probably never do it that was as there is no requirement to do so. Most times we just OPUS and move on from there. We very seldom start from a published mon, mainly because they are few and far between in our area, they aren't required, and it just adds cost with no added value.
@mightymoe In some states it was written even back in the NAD27 days that if a monument GS was within a certain distance then a tie to it needed to be made. Not a lot of people did that though cost and time. Plus most were just assuming 10000 5000 and holding a previous plat bearing. If I were signing my own work I would be doing as you do to a degree. Lat long and Datum. Epoch etc. I think the whole northing and wasting on a point causes more harm than good. Because someone inverses between the two points and the distance doesn’t match no meta data or it does match yet the coords look like state plane but are actually scaled and from where who knows. GIS gets it and places it they land in the ocean or some other county as they were scaled about 0,0. I say if tyrant ground distance fine on plat. Just place a lat long and now ellipsoid height at a couple corners. Bam done. Guess what if you do that you have everything you need to reduce the geodetic distance to ground between those two mons. You can compute the scale the ellipsoid factor and combined factor. Or cheat and use NCAT. We do make a note now so all the origin lat long height the height being what we used as a site along with the cf along with how you get from one to another. Meta data. My boss really likes to break it down. I do all tha math magically stuff and we worked together to develop a note. GIS can take lat longs so easily we all just about have that ability today in very minimal time. Maybe if GNSS goes away we would have to go back to astronomical lat and longs. lol.
Lat long and Datum. Epoch etc. I think the whole northing and wasting on a point causes more harm than good. Just place a lat long and now ellipsoid height at a couple corners. Bam done. Guess what if you do that you have everything you need to reduce the geodetic distance to ground between those two mons. You can compute the scale the ellipsoid factor and combined factor.
For property survey filings please use Lat, Long on the tie, forget any XY coordinates. Tell me the basis of bearings, if you express State Plane then tell me the scale factor used to get to ground. I don't need ellipsoid heights (if for some unknown reason that's needed, Google is available), multiple lat, long ties, one will do. If coordinates are given for some reason (can't think of a good one) then a full suite of metadata is required. If they are simple state plane then it's easy, state the coordinate system, zone and epoch.
Site surveys are a different animal, and you need the full suite of metadata for those since your setting site control and giving out coordinates. This all seems to baffle people, it's not really difficult.
Picking a point to scale from and not reporting where, that probably causes most issues. Not giving the scale factor is another one. I usually will puzzle it out quickly and move forward if I'm presented with ground coordinates without the metadata, but then I've been at it a long time.
@mightymoe if I gave you one lat long and ellipsoid height you have everything you need to compute the cf no need to list that. I do see your point. But take any lat long and ellipsoid height and plug that into NCAT. It will give you everything you need. Yeah northings and easting if on a plat should be in native form. Not scaled coordinates. That’s what happens where I live sometimes. Someone scales there project and displays the scaled coordinates and who knows from where. lol.
@mightymoe if I gave you one lat long and ellipsoid height you have everything you need to compute the cf no need to list that. I do see your point. But take any lat long and ellipsoid height and plug that into NCAT. It will give you everything you need. Yeah northings and easting if on a plat should be in native form. Not scaled coordinates. That’s what happens where I live sometimes. Someone scales there project and displays the scaled coordinates and who knows from where. lol.
Lets get the terms correct, Combined Scale Factors are related to a 3d point or the midpoint along a line connecting two 3d points.
A Project Adjustment Factor is a scale factor for an area of work. I have communities that all have Project Scale Factors. There will be hundreds of jobs within each Project Scale Factor area. DOT generally stops a scale factor after 10 miles of roadway, I've argued with them to sometimes extend that range along flat N-S roadways (TM projections), but they have balked. However, they seem to be changing. I believe that in the 60's and 70's when they used regional scale factors it colored their use of those later on as computer programs and distance meters showed up. But still a LLH on a tie point or a pair of points wouldn't give anyone the project scale factor. I try and keep a scale factor to a 10x10 mile square or 100 sq miles, think of a small ranch. Sometimes terrain makes it iiffy, I check how many PPMs are being created across the area, if it's within 10ppm meaning 400' of elevation or .999875 to .999895 grid scales then I'm good to go. I will certainly stretch that out to 30PPM. So, me giving you a LLH isn't helpful, what is helpful if I give the Project Scale Factor for the drawing/deed/plat/legal. Also ties 1000's of feet distance aren't the best. I followed a surveyor that was surveying a pipeline that ran mostly N-S through Montana, he had a brilliant process of switching the Scale Factor as he crossed township lines. That made it so easy to follow him. Montana is a special case the scale factors change fast north-south. But no, giving out one or two LLH pairs isn't the solution.
@mightymoe OK my Bad. I was looking at deriving a combined factor at each of the two points in your scenario. You would have a lat long height at say one point and then another at the tie point each one of those points would have its own unique cf. the mean at the midpoint of that line could then be computed. I see you have DOT project scale factors. We have something similar where our DOT gives the factor for each county and that is used on a lot of projects here. Some even use it for their non DOT jobs. So I believe you run TBC so do you apply that project scale factor at 0,0 or do they define the origin at some point on the project or are you using that for all measurements as you go.
@mightymoe OK my Bad. I was looking at deriving a combined factor at each of the two points in your scenario. You would have a lat long height at say one point and then another at the tie point each one of those points would have its own unique cf. the mean at the midpoint of that line could then be computed. I see you have DOT project scale factors. We have something similar where our DOT gives the factor for each county and that is used on a lot of projects here. Some even use it for their non DOT jobs. So I believe you run TBC so do you apply that project scale factor at 0,0 or do they define the origin at some point on the project or are you using that for all measurements as you go.
DOT multiplies the coordinates. I used to scale around a point, back in the instrument days we would develop a scale factor between two NGS NAD27 monuments, hold the one we started the traverse on, inverse between them, recalculate the second one by applying the SF to it and survey on ground coordinates from the first to the second one. That was a quick way to run 30 miles of traverses. Now I have many scale factors, I hate the DOT scales cause they want 9 places, or 1 part per billion.
I thought I watched a NGS webinar 6 or 8 months ago where a viewer asked the NGS presenter if they'd still need to scale from the new state plane and the NGS guy said yes. Is that not the case? Or am I misunderstanding what you're saying here.
I'm not sure what the question is referencing. I'd need to hear the question and answer. I see the NGS zone design criteria has been relaxed to 50 ppm. I thought it was once 25 but maybe I'm mistaken since that is our design criteria. In my opinion it is not useful to have a criteria that results in a need to be scaled to ground. It's also useful to remember that ppm varies inside a zone and the 50 ppm criteria is worse case. 90% of the area covered may be 25ppm or better. And the 10% may be in remote areas of the zone where 50 ppm can be accepted without causing trouble. Also it could be that the question and answer was regarding working in a statewide or special zone where ppm's are much higher. In summary, I don't think you were misunderstanding my opinion. Design a grid that works for ground. Why else go to the effort?
I was NGS guy for our state until I retired and that most likely would not have been my answer depending on how the question was framed.
I'm not sure what the question is referencing. I'd need to hear the question and answer. I see the NGS zone design criteria has been relaxed to 50 ppm. I thought it was once 25 but maybe I'm mistaken since that is our design criteria. In my opinion it is not useful to have a criteria that results in a need to be scaled to ground. It's also useful to remember that ppm varies inside a zone and the 50 ppm criteria is worse case. 90% of the area covered may be 25ppm or better. And the 10% may be in remote areas of the zone where 50 ppm can be accepted without causing trouble. Also it could be that the question and answer was regarding working in a statewide or special zone where ppm's are much higher. In summary, I don't think you were misunderstanding my opinion. Design a grid that works for ground. Why else go to the effort?
I was NGS guy for our state until I retired and that most likely would not have been my answer depending on how the question was framed.
I assume the NGS presenter gave the technical answer; when you put the coordinates on the new grid you'll need to from ground to get there and visa-versa.
The real question is: will it be worth it to bother.
I would love to be within 20ppm in all my work areas with a state wide system of zones.
Even 40ppm would be nice; as you probably know that's a range of 80ppm 40 up and 40 down. Which works out to about 1700' of elevation. And if designed correctly put the zone edges on high areas, zone CM's along lower elevations and you can extend the elevation changes and still say within the 50pm noted above. All of which is impossible in our mountain states, but much of the high ground is federal and who cares up there anyway.
I believe it depends on project specs on if you will need to scale between grid and ground. Unlike NAD 83 the map projection were either tangent or secant to the ellipsoid. Now the map projection will be weighted on population at the surface of those areas to minimize distortion at the surface AKA ground distances vs grid distances. So they have NGS does a GIS interactive map where you can look at the distortion in your state and areas. So if you have a project that has 20ppm and you can live with that then role on. I would caution work in the mapping projection would be smarter. All the math done for you. If you have more ppm for a project say 75 ppm but that meets your criteria then role on. If not maybe you need to scale or create a LDP that is tied to the datum which then allows for transformations to be computed from one coordinate system to another. One day maybe we will all accept we do not live on a flat earth and can go to Xyz lol.
If not maybe you need to scale or create a LDP that is tied to the datum which then allows for transformations to be computed from one coordinate system to another.
I doubt that will ever work. Users will want "official" projections that are available as defaults in all the major programs such as AutoCad, TBC, whatever Lica and Carlson use. If it's a roll your own, then it won't be useful for most. No matter how you do it you'll still have Scale Factors and rotations. Basically a scaled up State Plane is an LDP, the SF is tweaked to make it so. And anyone can divide the ground coordinates by the Project Factor to get back to SP coordinates.