In 2005 we surveyed the 10+ acre tract shown in red. In 2008 we surveyed and divided the 53+ acre tract outlined in blue. In 1999, an excellent local surveyor surveyed the 306+ acre tract outlined in yellow. The bearing basis of his survey was from Solar observations with an on site meridian (ie low convergence). His bearings agreed with our bearings to less than 20 arc seconds. Around 2002, the 76+ acre tract outlined in magenta was surveyed by another surveyor. His survey, while lacking in some areas, was technically accurate. His bearings were apparently based on a record bearing and this relation is about two degrees from Geodetic North (or four degrees from SPC Grid for this area).
Our current job is to survey out about 15 acres from the magenta 76 acre tract. Before going out, I was able to put the red and blue tracts into CAD in a common coordinate system, even though the two boundaries were never tied together directly, both had been tied to the NSRS. One by GPS observations to our office base station, the other to two city control monuments. I already had the yellow 306 acre tract plotted from the '08 survey and so, adding it to the CAD file was pretty straight forward. After plotting the 76 acre magenta tract, I was able to neatly orient it to the Eastern Northeast corner of the red tract and an angle in the West line of the yellow tract (the Southeast corner of the 76 acre tract). The comparative inverse between was impressively accurate (about a tenth of a foot).
Along the South line of the 76 acre magenta tract, about 2200 feet East of its Southwest corner is an angle corner, marked by a 3/4 inch iron rod in concrete, on the North side of a bank of Eastman pipelines. We needed this corner in order to place our 15 acre cut out on the line. In the field, we set up the RTK base on an arbitrary point for post processing, and did a single point localization on an easy to find point from the '05 survey. This localization was used only to facilitate corner search and was discarded after the post processing was performed. After localizing, we made our way to the angle corner in the South line of the 76 acre tract and found it easily. Occupying it for three minutes, we hit our predicted coordinates within 0.07 foot! All from tying to a single point 3000 feet away.
Good surveys, well documented, tied to good coordinates, based on reproducible bearings make boundary recovery incredibly more efficient. In '05 we had only just begun to do the extra work to make this possible. Now, having done this for more than a decade, we are beginning to enjoy the fruits of those labors, and as the patchwork densifies, of large and small boundary projects, we'll only continue to reap those benefits.
I love it when a plan comes together.
James
Looks good Shawn. Your example really drives home the usefulness of a known repeatable basis of bearing and/or a known datum.
I try to make a tie to a good SPCS location (usually by way of OPUS) when I am doing many projects. I have not found the value in doing so on ALL projects just yet, but that may be in the future for me (as you stated a lot in a well monumented subdivision is one exception).
It is really satisfying when you do a project and hit a few monuments beyond what you "need" for the survey. Then you get the call a couple of years later to work on a survey a couple of properties away and you can just key in data form the deeds, rotate and translate onto your "extra" locations and get a SPC as a search point for the new project corners that are tied into your previous work. Makes life a little easier.
"we'll only continue to reap those benefits"
I truly hope that means that your clients will getting charged for the time and effort you would have had to make if you did not already possess this information. Otherwise you are giving it all away.
Yes, it is important to make sure the compensation is there for the improved capabilities. And that's not always an easy thing to figure. For instance, in this very example, not only were we able to successfully navigate to the distant angle corner, recover it and locate it in, literally, a matter of a few minutes of arriving on the site, having never been to it before, we were also able to immediately determine the 3/8 inch iron rod we found at the Northwest corner of the parent tract was not the right corner - off by about 4 feet, and then found the right one. We also were able to determine, immediately, that another corner was 5+ feet from the nearby occupational chain link fence corner. How long might it have taken to discover that otherwise? What were the savings in time and effort? Determining a value on that kind of efficiency can be challenging.
