There was a thread a while back where people talked about finding sections that were 5280.00, and other unlikely events. I just had a similar experience.
When I examined my very first ever OPUS report (see thread), I was astounded by the agreement between it and my ÛÏclassicalÛ measurements of a monument in my front yard.
It is a screw in the base of a former flagpole in a very poor GPS location with the aluminum siding 20 feet north and leafless trees to the east and west, but it is about the best I can do at home where I can run the unit on AC power, and also I have triangulation/resection/leveling data I wanted to compare for that point.
The elevation was previously estimated by level run from hubs at a city drainage project a block away, and I wasnÛªt sure which datum they were using. The horizontal position was from my angle measurements to red lights on radio towers in a network involving some ÛÏknownÛ points around this end of town. If I knew for sure which datum realization the ÛÏknownsÛ were on, the least squares tells me I have a standard error of about 0.1 ft, but I suspect some are on various realizations.
So I was shocked when the difference between OPUS and classical measurement was only 0.021 ft (+/- 0.7 ft) vertical and 0.033 ft (+/- 0.260 ft) horizontal.:-O ThatÛªs like throwing a dart blindfolded and getting a perfect bullseye. It feels good but you know it was an accident.
I need to do a session on a HARN station to really check myself, and IÛªd be pleased if it matched that well.
I donÛªt know yet if I can get the lithium batteries in the antique receiver replaced without losing the firmware so that I can work in the field without AC and bring data home. But Rankin said he was sending it on a trial basis, and if I pay shipping to send it back, IÛªve gotten that much moneyÛªs worth out of it in education already.
Bill93, post: 341817, member: 87 wrote: When I examined my very first ever OPUS report (see thread), I was astounded by the agreement between it and my ÛÏclassicalÛ measurements of a monument in my front yard.
The elevation was previously estimated by level run from hubs at a city drainage project a block away, and I wasnÛªt sure which datum they were using. The horizontal position was from my angle measurements to red lights on radio towers in a network involving some ÛÏknownÛ points around this end of town. If I knew for sure which datum realization the ÛÏknownsÛ were on, the least squares tells me I have a standard error of about 0.1 ft, but I suspect some are on various realizations.
So I was shocked when the difference between OPUS and classical measurement was only 0.021 ft (+/- 0.7 ft) vertical and 0.033 ft (+/- 0.260 ft) horizontal.:-O ThatÛªs like throwing a dart blindfolded and getting a perfect bullseye. It feels good but you know it was an accident.
Now it would be interesting to independently determine the positions of the red lights on radio towers by triangulation from OPUS positions to see how the coordinates used in deriving the resection solution for the base position compare. Whatever you do, though, don't use RTK since anyone who has read this message board will know that it's always exactly on the money (unless it's off by more than a decimeter or a foot or five).
