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Transferring points on cad drawing to total station

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  • 19-10-2012 5:04am
    #1
    memaul
    Registered Users Posts: 202 ✭✭


    Hi folks,

    Can anyone advise me of a quick way to transfer points from a cad drawing straight to a total station.

    I have heard of scripts that will write a csv file for all the nodes on a drawing that can be transferred to a total station.

    Any advice?


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    #2
    kc20010101
    Registered Users Posts: 3 ✭kc20010101


    Hi, maybe you could help me out?

    Its been a long time since I used a total station but need to help out a friend if i can. Just want to make sure of a few things. I have a Topcon 226. Basically I need to survey a simple site, set up control points and be able to set up again at a later date to set out.

    I am trying to remember but havent had a chance to try it out yet. If I set up in a random spot and call that the occ pt. say 100,100, 0. when i import that to CAD and have fixed points such as corner of an existing house of other fixed points, the co-ordinates shown on cad could be used as station co-ordinates. Would that be correct??

    Also the process for re section and occ pt for setting out would be great. Cant find a step by guide anywhere.

    Thanks in Advance for any replies.


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    #3
    Supertech
    Registered Users Posts: 597 ✭✭✭Supertech


    Firstly give yourself plenty of scope with the opening coordinates. Look at the size of the site and set it up appropriately - E500,N500,Z100 or whatever. That way you won't have negative coordinates on the drawing. Just make sure that the base coordinates for your occupied point will allow you sufficient distance to measure the entire site in positive coordinates and you'll be fine. It will make life far easier for you in manipulating the drawing.

    Secondly, give yourself at least three fixed points to set back up from - timber pegs or washered nails are best. Record these first and make note of the coordinates. This will provide the basis for your set up when you come back. Leave the pegs or nails in place, and obviously in locations where they won't be disturbed. Corners of buildings etc are not reliable for setting back up into a survey accurately unless you have very well defined points. I prefer smaller markers that I can be 100% sure of.

    I'm not familiar with the Topcon instruments, but I'm fairly sure the prinicple is the same with all total stations. You will be exporting from the instrument in csv format. There's a free software called Datalink (Google it) which will convert csv files to dxf files (and vice versa). These can then be opened in Autocad. When it comes to converting for setting out purposes, you simply allocate 'nodes' to the relevant points, strip everything else out of the drawing and go through the same process backwards, loading the converted csv file onto the instrument when it's complete. (If there's only a small number of set out points, you could, as you say, take the coordinates from the CAD drawing and input them manually to the original survey file on the instrument) PM me if you get stuck.

    As for setting back up, you've two options :

    1. Set up over one of your known markers and backsight to a second. Use the third one as a check to ensure your coordinates are correct by taking a reading onto that location once you're set up accurately.

    2. To resection, set up in a location where you can see all of your 3 pegs or nails from. Try to get an equal distance and angle from any two of them, so that a line from your location through each of these markers and back to you forms a decent triangle. You'll normally be prompted by the instrument for a height at that location. Make sure the instrument is set up accurately and then tape the height to the appropriate location on the instrument and input it accordingly. You'll normally then be prompted for a known point (one of your markers) so select that from the file on the instrument and measure to it. Then at the appropriate prompt measure to the second known point. Once the total station has two known points, and a distance to each of them, it should be capable of calculating your new position. Once you save that as your location, check back to the third marker to make sure your coordinates are correct. If they are, you're good to proceed as before. Stakeout is normally just the reverse of measurement, but obviously it takes slightly longer as you'll have multiple shots at each stake out point to get it correct. Good Luck !


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    #4
    kc20010101
    Registered Users Posts: 3 ✭kc20010101


    Thanks Supertech. It actually came back to me when I went at it. One other question for you, if I am given a cad drawing without any stations, to set out a building could I use the coordinates directly off the drawing? I can use fixed points of the layout. surely more accurate that taping?


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    #5
    Supertech
    Registered Users Posts: 597 ✭✭✭Supertech


    You would need to survey in sopme points that are common to both the site and the drawing that you have in order to establish a relationship between the two, so pick at least two sides of two buildings so you can establish their positions. once you have these, you can than overlay your drawing onto your site survey and set out accordingly.


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