Page 1 of 1

Sureyor data, CRM's, UTM's etc.

PostPosted: Tue May 19, 2020 8:48 pm
by Mark Bell
There's a push from contractors and their surveyors for set out measurements to be in UTM Northings and Eastings (X/Y) format (and sometimes X/Y/RL for spot heights) which only requires a reference point noted on the drawing and the corresponding coordinate table making it easier for the surveyors to do the set out compared to referencing grids with offset dimensions. Unless I've missed it, the Scale Type menu doesn't appear to offer this option?

Using an online Lat Long to UTM converter, a site's E+N can be calculated which can be cross checked against survey data. If we then need to document the E+N coordinates, particularly for hard landscaped areas in a project how does DataCAD create accurate E+N coordinates on the drawings? Can these new coordinate points also be output to say an Excel format?



Re: Sureyor data, CRM's, UTM's etc.

PostPosted: Tue Aug 11, 2020 11:19 pm
by seasdes
That doesn't seem right to me. I think UTM coords can change over time. Therefore if the project is shelved for a number of years after design then the location coordinates will change.

Therefor surveyors should be given dimensions relative to a known reference Ie property boundary etc.

A question to the surveyors out there.

Just thinking.

Re: Sureyor data, CRM's, UTM's etc.

PostPosted: Wed Aug 12, 2020 10:24 pm
by Ted B
The drawback in any modern ultra-accurate system is the Earth moves. Greenwich-Zero is no longer through the Observatory Dome at Greenwich. All of Australia was relocated by 700-ft in GPS due to Continental Drift not that long ago. I'm in a metes-and-bounds jurisdiction so closing errors still are common, especially with old surveys done with hand equipment, sliderules and longhand calculations. Old local magnetic bearings just add to the fun with local deviations and a moving Magnetic Pole over time.

One the gripping-hand it's extraordinary how repeatedly-accurate the systems have become with a local fixed-point transmitter added. My farmer friends have GPS in their machines that let them plow and plant with repeated sub-inch accuracy. That same acuracy is applied to earthmoving equipment and foundation spot-locations and elevations.

One archaic remnant I deal with is Degree-decimal Minutes. It's still used in Celestial Navigation and Nautical Almanacs instead of degrees-minutes-seconds ...and in really old surveys. The star charts and lunar tables are tabulated and positions reckoned at sea in degree-decimal minutes. As are the Verniers on my sextant. I have a brass transit of my grandfather's that's well over a hundred years old that is graduated in decimal-minutes. (Both of my grandfathers were surveyors, one became an Architect and the other was a civil engineer and artilleryist.)