Our GNSS rovers are currently unavailable, so we're using total stations only. We started our route survey, no elevations, by setting 2 control points about 600' apart with assumed coordinates on occupied point 101, then setting point 102 with the intent of using an assumed bearing of due east. We took a side shot on 102 in order to get coordinates on it for our traverse. The inverse distance 101 to 102 was 0.23' longer than the total station measurement. I thought that was a bit much for such a short distance and with a vertical angle of near 90?ø. The fix was checking the Use Grid/Ground box. We still aren't comfortable with this, so I volunteered to do some research for the crew. I'm posting this topic for some help. We never used the Use Grid/Ground box before. I've attached something from Topcon concerning this for those who are unfamiliar with the software.
Find?ÿ the grid/ground factor for the approximate lat/lon and elev from some source and see if your observed values are in the ballpark using that factor.
You could use CORPSCON or your proprietary software, or a nearby NGS data sheet to get the factor.
I'm posting this topic for some help. We never used the Use Grid/Ground box before.
Please do ask for education, training, and support. There is no place in Florida where the grid/ground scale factor would equate to 0.23' in 600', that's 1:2608.?ÿ
Sorry for THE rant. I just hate to see this over and over.
If you read the output in Magnet Field, it probably says Geodetic Dist or Hdist or Ground results? Sounds like you are looking at the Geodetic Distance at the very bottom of the page, further up the page you should see HDIST.?ÿ
It appears your data collector is configured to State Plane coordinates which expect coordinates in the millions, yet you are using an assumed coordinate system near 5000. So when you inverse in the software with the SPC set you will get a "GRID" distance and a Geodetic distance on the ellipsoid. This is not the ground distance you measured with the EDM.
The simple fix here is next time set up the project correctly by changing your Coordinate System settings in Magnet Field to No Projection / No Datum / No Geoid which will then be on a ground assumed coordinate system. I say "next time" because if you change these settings now, it will not work as the software will not have enough Geodetic coordinates to convert your datum. It is just sad to think you have been using this for over 5 years now and your office does not get the training or education you deserve.
Seems like nobody ever has the time to get us training on any software. When I was using magnet field I was all on my own and nobody else I worked with used it. The salespeople were the only real help and in the end I figured out I knew more than they did about some aspects of the software.?ÿ
Most of our jobs were 1:1 so it was always use grid/ground. My only issue was applying a scale factor which there were 2 different apparent ways to do it and I apparently picked the wrong one so it never worked right forcing me to switch back to fieldgenius.?ÿ
I used a bunch of training videos I found and posts by Leegreen to figure this software out. In the end it was my favorite software out of it, fieldgenius and Trimble access and one day of Carlson survPC trial.?ÿ
This is our first experience using the collector for a 1:1 job. We understand, as Lee points out, that all parameters need to be set during job creation. We didn't know that, but now that we do, we won't make any changes now because we're already into the job. Our first inclination was to use no datum, no geoid, and set the SF to 1. When this didn't work, I suggested we use the Grid to Ground option.
I think Lee figured it out. SPC 5000 is probably out in the gulf somewhere, and would have a vastly different scale factor than your location.
I appreciate your patience with my situation. We now have an understanding of how to make this work properly. I was able to create my own Topcon account even though I don't own their software. I got the attached images from the Topcon website. While I'm somewhat familiar with projections, SPCs, etc., I needed to know how to make the software work the way I do. It's too bad that there isn't a good Topcon video out there that explains this using a real field project as an example. At the present time, the only training available to me is what I dig up on the Internet, and the kind responses I get on these forums.
Seems like nobody ever has the time to get us training on any software. When I was using magnet field I was all on my own and nobody else I worked with used it. The salespeople were the only real help and in the end I figured out I knew more than they did about some aspects of the software.
I've been having this discussion with our leadership for a while now. When we switched to Trimble, I argued for an internal training program, got rejected, put my foot down, and eventually found myself in charge of running field and office training.
We've made some progress, but I'd say no more than 10-15% of crews really know the software well, or are interested in understanding it.
The fact is that modern field software has to be extremely flexible and cover a lot of ground in order to be useful to a wide enough customer base. GNSS throws a whole lot of additional issues into the mix that must be dealt with, requiring users to have a firm grasp of what's going on under the hood to really make the software sing.
The real shame is that a good deal of the project leads, and even the field leads (like chiefs of parties) don't really know the software very well either, and aren't interested either. So the ones who should be passing knowledge down, and troubleshooting issues on a project-by-project basis, have basically given up. There's no shortage of information to learn from, from manuals to tutorials to online recorded webinars to YouTube videos.
Why don't people put the time in? A good chunk of surveyors treat field and office software as a nuisance or roadblock, a necessary evil, rather than a tool of the trade to be fully understood and mastered.
These same folks will nerd out over older gear and beat their chests while discussing how well they could wrap sets with their old Wild or Kern theodolite. And a lot of them really were good at it. I missed out on that era, but I had to master my manual Leica total station and the TDS software running on my HP48 data collector. I just didn't consider it any different when I switched to Trimble, then Leica, then back again, with some Topcon in there too.
Leadership at survey/engineering firms still tends to think of field and office software as being simple push-button concepts. That's wishful thinking. This stuff has gotten more complex and demands more from the operators.
I think it's a good thing. We have more tools at our fingertips than ever before. But it requires the right attitude from both leadership and from field and office operators to make the most of them.
As Lee touched on if you have SPC of some flavor set into your Data Collector and then use an assumed coordinate of say 10000, 10000 the DC "thinks" you are near the origin point for the zone.
The scale factors at a location like that would be distorted. I wouldn't even try to figure it out.
You need to not ever do it again if that's what you're doing.?ÿ
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One last comment: We had our crews use separate files for GNSS and total station work - not that it was necessary. We always configured the total station work to no datum/ no projection. It just made things less likely to get messed up. We had a few times when someone tried something like this that drove that decision. It can be avoided with proper understanding gained through training however as we have seen it takes some longer to gain proper understanding than others. Less risky to remove the risk.?ÿ
I'm not getting where the software correlates the 5000,5000 to any grid or geodetic coordinate.?ÿ Do you make that connection somewhere??ÿ If not, it may be thinking you're 100's of miles west and would definitely throw a wrench in a transformation.
@dave-o?ÿ
That's what he did. He told the software he was working on the ground hundreds of miles from where he was in a geographic sense. The software gave him the correct ground distances if he was working where he told it he was. It would have worked ok if he would have been surveying using the approximate state plane coordinate of where he actually was. 3,000,000 N 1,000,000 E or whatever.?ÿ
I took a quick look, the Florida East Zone origin point is south of Marathon in the ocean, but the false easting for the origin point is 200,000m so the DC is going to be surveying 200,000m west in the Gulf west of Key West. The scale factors will be interesting and the resulting Grid distances should be longer than ground since you are surveying above ground.?ÿ
