Sketching and Baseline


My last few projects have been low budget, no survey team, minimum field support, and no one available to assist in field data gathering. Sometimes you have good drawings of the existing units, but often you need to sketch the whole thing.

So, here are a few hints on setting up your sketch and establishing a baseline for dimensions.

  1. Check the area for structure, be it piperack, platforms, equipment, fencing, etc., and use as your sketch baseline.
    If there is some distance between them, use colored twine to stretch between to measure to.
    Use duct tape to tape the twine to the structure to make sure it doesn't slide down or slip off.  
    You'll probably need to verify north/south line baseline.
    Also make sure that you establish the baseline at a known height of concrete pad or structure.

  2. Sketch all the item that you need in your project plan to adequately make you modification to.
    Note where drains and sewers are, power lines and boxes, manways and access points to the area, and any nozzle and tie-in points that you need.

  3. With your baseline established start pulling measurements to it.
    If you have a partner, this should go fast, with one holding the tape and one reading measurements and taking notes.
    Most of the time, I'm doing this alone, so I use magnets to hold the tape in place or have magnetic tips on my tape.
    I keep several of each in my field bag.
    Just a note, if you do use magnets, keep them in a separate bag and away from your laptop bag and portable drives.
    I usually check this bag at the airport to avoid taking it through security.
    My field bag not only has magnets, but multi-tools, stakes, d-clips, mirrors, flashlights, markers, survey tape and colored duck tape, several rolls of twine, several plumb Bob's, tennis ball, torpedo levels, line levels, dry eraser board and markers, and grease markers and Sharpies.
    I also have a tape that is for measuring diameters of pipe, so if I have a question in the piping I am looking at, I can verify with it, or measure the circumference of the pipe to get the OD.
    Yep, it weights about 35 pounds when I add my winter FRP, hard hat, FRP rain gear, and gloves.

  4. To keep your self square in measurements, pull from the object to your baseline.
    You'll notice that there are ruled marks on top and bottom of the tape.
    Slide the tape along the baseline till both side of the tape read the same or the marks line up with the baseline.
    This will so you that you have squared your tape with the object and have an accurate measurement to it.
    Take all your measurements and add them to your sketch.

  5. For elevations, use the baseline as well.
    Attach another length of twine to the object at the face of flange, top of support, etc., and pull to the baseline.
    With a line level, stretch the line till the line level bubbles boxes and take a measurement between the lines.
    If the pad is level, I just measure from the object to top of pad.
    If you have objects overhead, measure down to the baseline to establish an elevation.

  6. Always get help from unit operators.
    Your going to need to know where underground piping, conduit, and sewers are.
    You can see some of these objects above grade, and if there are several of them, you can locate them between what you see.
    But most of the time, the operators will have to help locate them.
    Add them to you sketch. Oh, while the operator is there, tell them what your project is and see if they have any suggestions on layout, operations, or maintainable clearances you need to consider.
    If these guys don't like what you're designing, you might get bad reviews.
  7. Finish up by taking photos of all you have sketched.
    Don't get to close that you can't establish what you looking at.
    If you need close pictures, use a dry eraser board, identify what your taking a photo of, and place it beside the object in the picture.
    It also helps if you go to the corners of the area and take panning photos from all sides.
    Don't forget to get overhead photos also.
    And if you can safely climb, take an overhead of the area.


Hope this helps. Be safe in the field.

Things you'll find in my field bag

Graduated Scale

The lines match on both sides of the tape, so your tape measure is square with the object.


Grease Markers


Plumb Bob

Torpedo Level

Construction Twine

Duct Tape

Line Level

Tape Measures





About the Author


{cb:Lee Smith is the Owner/Operator of Smith Design, CADWorx and AutoCAD experienced,}

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