the original data sheets are what you??d expect- SPC northings, eastings, and geoid referenced elevations, along with a vicinity sketch with ties to several reference points. but I??ve never once seen a check-in or any evidence of updated info on one. I suspect that, when set, there was likely an expectation and/or desire that a robust network would be maintained and referenced, but it just never happened. And I haven??t done a ton of projects FOR the city, but I??m about 99.9% positive their own control doesn??t even register on their radar when such projects are done.
Well, the published coordinates are indeed worthless for surveying. It turns out that the ratios of the SPC Northings to the City Northings is greater than 1 while the ratios of the Eastings is less than 1. The product of these ratios is almost equal to 1, meaning that they are very close to being reciprocals of each other. See the updated spreadsheet attached.
The result of this is that a distance calculated using the City coordinates will be almost equal to the same distance calculated using SPC. In other words, the City coordinates do not produce ground distances at all.
This is nuts. If you want your GIS to produce SPC grid distances, why not just use SPC coordinates?
GIS could be a valuable tool for everybody with no more work required than it takes to invalidate it for surveyors. Probably too much to hope for at this stage, though.
?ÿ
@mathteacher the datasheets should also tell you what type of monument was set. Just a set of coordinates isn't very useful if you get out there and find multiple monuments within a reasonable distance of those coordinates. Would love to explain to the board that I held the pretty "X" cut on the back of curb that had three different colors of spray paint on it when the City actually set a rod with brass disc just behind the curb that was covered with grass.
@flyin-solo sadly the City of Lubbock control is similar. Lots of the control points were set in the middle of intersections for aerial targets and no ties were given to other permanent markers. Growth of the city has pretty much wiped all of the control in the Southwest and Southeast side of town out. However data sheets are available and if anyone is ever in the area they are free to contact me and I can help them out with that.
Thank you all.?ÿ I really have stumbled into a pool of knowledge finding this forum. I was reluctant to reach out here, but I am glad I did.?ÿ?ÿ
Don't hesitate.?ÿ Jump right in with either more questions or tell some stories about your work.?ÿ We are listening, as they say.
@cyril-turner wish'd i'd have thought to get hold of you about 6 months ago when out was out in amarillo shooting a title and discovered there wasn't any network coverage anywheres...?ÿ made for an impromptu static exercise- something i hadn't done in a few years...
Austin survey monument data sheets are now available online at:
https://austintexas.app.box.com/s/jxcoivasacx1kctgixkj7jyhzr6x0zkx
?ÿ
?ÿ
?ÿ
?ÿ
?ÿ
?ÿ
?ÿ
