SPCS

Posted by: @shawn93

As I don't live in a state with CORS or RTN

Welcome to the site. This is a scary question if it is coming from someone portraying to be a self employed professional surveyor. Are you licensed or just a construction layout person?

There are CORS is South Dakota,?ÿ not many though.?ÿ So I would post process static observations using Magnet Tools with your Hiper VR data to take advantage of GNSS. As CORS will only process GPS.?ÿ

To supplement Lee Greenƒ??s post I attach three images showing that there are CORS in SD, the location of NGS published monuments near Pierre, SD and a datasheet for one of the points that shows that SPCS coordinates are included on NGS datasheets,

As for your final question: SPCS v ƒ??hereƒ? coordinates, the NSRS exists to allow users to set their receivers over NGS published sites or connect via the NCN/CORS in order to attach to the national spatial reference system (NSRS). Without such a linkage how do you exchange data with others. An autonomous position would be with respect to the satellites which are in the current implementation of WGS84. NAD82(2011) is not equivalent to WGS84.

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?ÿFor more information about these issues, I suggest contacting your NGS Regional Advisor Dave Zeno.

Dave Zenk, PE, LS
NOAA/NOS/National Geodetic Survey
University of Minnesota, Geography Department
414A Social Sciences Building
267 19th Ave S
Minneapolis, MN 55455
Office: (612) 626-6175
Mobile: (612) 414-9522
Email: Dave.Zenk at noaa.gov

@shawn93

It appears Topcon Topnet Live is a VRS that is available in your area near Sioux Falls, SD.

Be careful if you are offering surveying services without a licensed surveyor in responsible charge. There might be some gray area when it comes to incidental mapping during a layout project, but offering to perform topographic mapping using surveying principles is considered practicing land surveying in SD.

So if you've been doing stuff in-house up to this point, it might not matter, but you say a client is looking to hire you specifically to perform mapping services. That likely requires a license (see #4):

It takes a fair amount of reading and studying, and usually some work underneath a knowledgeable surveyor, to really grasp the critical differences between SPCS and local or assumed datums. (There's not really such a thing as a "here" coordinate system - the here position can be in any system you want it to be in.) GPS on BM is an NGS program (as opposed to a reference frame), and setting your base on a benchmark might get you bogus coordinates since BMs are often vertical-only and their "SPCS" published coordinates are very rough - sometimes less precise than a here position might be.

Plus, if you're going to run a "large-scale" project in SPCS, you need to understand what that means in terms of distortion, especially if you're going to be doing precision layout at some point.

There are ways to mitigate and/or remove the distortion, but figuring out how to approach that and all the other issues is precisely why the practice of land surveying is regulated.

Thanks for the tips guys. I guess a better description of who I am and what I do would be: "I'm more of a MEP building "contractor" who has discovered the conveniences of using CAD drafting and Positioning systems to layout construction and utility points." Occasionally I'll have a "bud" call me up and they'll ask me to square off a building for them or set some offset points for building corners. As far as engineering or surveying for government or engineering firms, I don't intend to step in and try to do their work for them or try to overstep my boundaries. Most of what I've learned from positioning systems I got from the field, online, or occasionally talk to a professional surveyor.?ÿ

Again, thanks guys for the insight!!

Posted by: @shawn93

.... my question basically is: Is there a benefit over being on SPCS vs. a "here" coordinate system ...?

I see 2 major benefits: 1) recoverability of the coordinate system even when all local marks are lost, and 2) coordination with the work of others, particularly GIS and other outside sources.?ÿ For me, and the kind of work I do, there is a 3rd benefit and that is that as I accumulate projects on a common coordinate system I eventually find myself able to tag on to previously completed projects and thus easily reuse data. This may not be a big deal for you.?ÿ

As others have indicated -?ÿ working in a grid system, while not rocket science, does require some specialized knowledge and training.

One relatively easy way to establish a grid coordinate system is to collect satellite raw data at the RTK base for submission to OPUS.?ÿ ?ÿOnce you have the true NSRS position of the base you can shift the collected points to correspond. There are various ways to accomplish that shifting. You could use CAD or Excel. I use StarNet. Lots of other options.?ÿ?ÿ

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@norman-oklahoma your second reason stated for using SPCS is my biggest reason for wanting to go with that coordinate system. I find it much easier to attach satellite imagery and other GIS data to my surveys if I use SPCS. Whereas in the past I have done it with just the LatLon coordinates of my control points.

So if I setup base and have it collecting raw data as I am establishing my control network (about 2-4 hours) I can just take those raw data files, convert to rinex, and submit to opus and that will give me the SPCS coordinate of my base and just shift my points in ACAD (which is what I am currently using) to match with OPUS control point and DONE! Right?

@leegreen the closest TopNet Live VRS to my location is the one located in Niobrara, Nebraska. Which is about 25-30 miles as the signal flies. But at this point I am not setup with TopNET Live and my receivers do not have a cellular modem on-board.?ÿ

Posted by: @shawn93

Can I just set my Coordinate system to SPCS and start up base

You can do as you ask if you put your base out on a previously GPS observed control point such as NGS Cooperative Base Network Control Station designated 46 317.14 located ABOUT 5.0 MI SOUTH-SOUTHWEST OF SCOTLAND, ON STATE HIGHWAY 46.?ÿ

NAD 83(2011) POSITION- 43 04 56.73329(N) 097 44 30.61670(W)

Your base coordinates in SD South Zone are N=283,823.57 E=2,660,708.71 US FT

GPS observed Height=1388.10 computed using Geoid 18?ÿ

In your Magnet software job configuration you would want to use NAD83 (No Trans) for a datum. You would also want to configure to Geoid 18 to use the marker height.?ÿ

Posted by: @shawn93

@leegreen the closest TopNet Live VRS to my location is the one located in Niobrara, Nebraska. Which is about 25-30 miles as the signal flies. But at this point I am not setup with TopNET Live and my receivers do not have a cellular modem on-board.?ÿ

You can use a hotspot or wifi with the controller (FC6000) for your internet connection, no need for a modem inside the receiver. 25 miles is at the limit, give your dealer a call for a demo of TopNET live.?ÿ

Posted by: @shawn93

1)..... in the past I have done it with just the LatLon coordinates of my control points.?ÿ

2) ...... and submit to opus and that will give me the SPCS coordinate of my base and just shift my points in ACAD (which is what I am currently using) to match with OPUS control point and DONE! Right?

1) The HERE position is typically within about 10 feet of the true position.?ÿ A state plane coordinate is merely a conversion of the spherical lat/long format to a plane northing/easting format. The lat/longs you get based on a HERE position are not any more accurate than the northings/eastings.

2) Right. Your dc needs to be set to the appropriate state plane zone while you are collecting points so that the vectors are scaled appropriately. Even better would be to determine the correct SP position for your base in advance, set your base up with that position rather than a HERE, and then you can dispense with moving coordinates around.?ÿ ?ÿ?ÿ

One day we were using a hotspot on a remote job near a river.?ÿ We could see the cell tower about three miles away.?ÿ Suddenly, we couldn't get a fix.?ÿ We tried to think of every possibility.?ÿ Gave up.?ÿ Learned later that cell tower had been shut down due to some big problem.?ÿ Had we gone to the site one day later everything would have been great.

Posted by: @shawn93

@norman-oklahoma your second reason stated for using SPCS is my biggest reason for wanting to go with that coordinate system. I find it much easier to attach satellite imagery and other GIS data to my surveys if I use SPCS. Whereas in the past I have done it with just the LatLon coordinates of my control points.

So if I setup base and have it collecting raw data as I am establishing my control network (about 2-4 hours) I can just take those raw data files, convert to rinex, and submit to opus and that will give me the SPCS coordinate of my base and just shift my points in ACAD (which is what I am currently using) to match with OPUS control point and DONE! Right?

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@shawn93 not quite.?ÿ The amount that you may be in error doing this this way has to do with your SPCS coordinates versus actual ground coords and distances.?ÿ That may be negligible for what you're doing, but it may not be, and it'll depend on both your specific location on the particular SPCS (distance from central meridian and baseline) and your "elevation", which is another term that in this area serves us best by understanding more thoroughly - thus the cautions from others here to understand this concept (SPCS) well before applying it to measurements you're making for design or construction.?ÿ It has great value, as rover mentions, but it's value is in recovering ground accuracy not necessarily ground precision.?ÿ Surveyors, I find, see many things much differently that most of the rest of the world. Good on ya for asking these questions.

@leegreen quick (stupid) question. Assuming that I would go with TOPNET Live VRS corrections and assume I would be using the nearest VRS. Being the station is located in Nebraska and I'm on the South Dakota South SPCS would it still send me the same corrections. What my question is; No matter what SPCS the VRS is located it in the corrections that I receive from that station are simply "cleaned-up" satellite signals which will only ensure that my LatLon is accurate, thus placing me precisely on the SPCS that I have selected as my projection?

My apologies if I sound like an 8th grader.?ÿ

@shawn93?ÿ

I commend you in asking and wanting to learn. They always say there is no stupid questions. However if you're providing services to clients based upon limited knowledge,?ÿ then your clients have a fool for a surveyor.?ÿ

To answer your question. It doesn't matter what state or what country the CORS is located in, you can get good results only if you understand the datums, projections, geoids, Ellipsoid,?ÿ International feet, and GNSS procedures. It is not the system that will make a mistake, with out proper training and knowledge you will make a stupid mistake. I see these simple mistakes by made my large successful engineering firms many times, where their licensed land surveyor does not understand the process. For example this may sound stupid, just selecting the wrong measurement of a foot, International or US,?ÿ will make your coordinates wrong.?ÿ

The best you can do for your clients and your reputation is learn how to do it correctly.?ÿ

Please go to my website leegreen.com if you want help learning how to do this properly. I provide consulting services to contractors like you.

@shawn93 easiest way to put this is the base station in Nebraska is sending corrections in lat/long (I'm oversimplifying this) and your rover receives those corrections in lat/long. The conversion to SPC doesn't happen until the software in your collector makes that conversion.

@cyril-turner that's kinda what I had in mind. I just wanted to verify if I was seeing things in the correct perspective.

It's good to remember that when using a real-time network, we are at the mercy of the network operators/admins. Depending on what gear you are using, you might be limited to certain mountpoints. Some networks are very robust and serve a wide range of needs, others are more limited.

Other considerations are: can you get network solutions or single-base only, full constellation versus only one or two? Which reference frame and realization is being broadcast and is that the correct one for your work? If not, how (or can) you transform in your DC during data collection?

Don't even get me started on vertical datums and RTNs...

@rover83?ÿ

Amen!