OPUS Projects vs DIY

john-hamilton · 2014-03-05T15:45:00Z

I am building a height mod network, mainly to position my pedestal in the NSRS but also to get some good GPS on benchmark observations. I plan on bluebooking it so that the new mark will be published. It is not yet complete, I have one more benchmark to add to the network in the SW and repeat obs on the three in the NE. The final network will have all lines dup'd. The way OPUS projects works is that it uses the CORS that were used in all of the individual OPUS static solutions, but it processes the connecting lines as well (i.e. lines between stations that have common observation time). There are several ways to pick which non trivial lines are processed (and you can process all, both trivial and non-trivial). I processed in TBC (using one CORS) and adjusted using Geolab, holding only the CORS (the open circle at the top) in lat,long, and ellipsoidal height. I then checked the vertical misclosures, in meters, (NAVD88) at the benchmarks:PID TBC/Geolab OPUS ProjectsDN6056 0.000 -0.035KX1261 -0.011 0.052KX2400 0.017 -0.052KX2401 -0.002 -0.049KX2402 -0.006 -0.024KX2442 0.001 -0.017KY0376 0.032 -0.072KY0391 0.003 -0.040All of the sessions were minimum 120 minutes, most were much longer. I note that all of the BM's have significantly better misclosures from my processing/adjustment than does OPUS Projects (same constraint). That also means that GEOID12A is very good in this area. Once I get all the lines observed and processed, I will do a comparison again, and also compare the final constrained adjustments.I am not yet ready to start using OPUS Projects. I do not see the advantage at this time (I didn't see it when I went to the class, either).

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Strictly Surveying

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MightyMoe

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yes, I know, that's why I was saying you had over .3' difference on the one bench mark, or .1m. Just converting in my head;-)

Wrongly used that .3'(.1m) of difference can cause all kinds of havoc.

And I've seen that happen too often.

I think it's great that John is analyzing his network this way, checking between OPUS, TBC/Geolab, single CORS against multiple CORS and bench mark elevations. It's like he is a real surveyor.

I just wish more surveyors took the time to run control correctly and took the time to find out just what the numbers are telling them.

Posted : March 7, 2014 3:06 pm

Kevin Samuel

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Not to mention the possibility of being mid-project when a government shutdown occurs!

Posted : April 4, 2014 6:27 am

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OPUS Projects vs DIY

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