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Replies
Hello! I always did this on three control points in AutoCAD (the third for control), the ALIGN command or simply by transferring the cloud of points to the original one, and then I chose the reference angle and turned the cloud of points to the second reference point, the third point shows the quality of your work! The quality depends also on the accuracy of determining the reference points from their real value (therefore the reference I use three points)! For long distances there will be inaccuracies, you yourself will see them when rotating! When importing, look at the number of decimal places at the control points and at the shooting points! Of course, you can do it in GPS immediately, but I did not have the need for it!
do you mean rotating the data in the drawing or auto-cad - find out the swing angle properties and from there you can work them out . If you are using assume coordinates or assumed bearing when you first started your topographic job then it is imperative to know what are the actual values of the datum you used .. Other wise you have to go back to field work and connect you survey stations to known points. ( working from the whole to the part)
Maybe I misinterpreted the question. I thought he said topo data? Topo data is 3 dimensional. Geodetic measurements are curved, rectilinear measurements are in a straight line. Yes you can rotate objects & lines in CAD but the coordinate values can suffer. A better solution if you are working in Autocad is to use something like Carlson. I like PROCOGO, it is relatively inexpensive & runs in Autocad. Converting geodetic elevations to a local datum could be a bit sticky as our British friends might say.
I think he meant the maps projection coordinate system ..national grid system .. every country has it own coordinates origins. they varied from one another depending to the map projection used to defined the origin....
It is not vey clear for what reason he wants to rotate it. I just wonder what kind of jobs can you do in Walterborough as a land surveyor?
https://www.youtube.com/watch?v=9FrSD5ipSMI - around minute 2:00 it starts where he uses UCSMAN command - in portugeses but it does not matter
Man try UCS command in Autocad and UCSMAN is another. THere is no need for rotating anything. Rotating has a downside in CAD as the accuracy is lost very often especially when there is lots of points. You see CAD has its downsides and this is one of them. When using UCS it works much more accurate. We are talking milimeters when rotating but still. Each time you rotate it will shift.
Above will apply to data on an area of max few kilometers wide.
For the roads or the data which covers longer distances you would have to apply corrections to cover for the curvature of earth. Mr CHARLIE B. AYCOCK, III covered it already quite well.