GSSI SIR 4000, Manual

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Geophysical Survey Systems, Inc. SIR® 4000
Manual
MN72-433 Rev F 60
4.2: Setting Up a Physical 3D Grid
Collecting data for 3D processing and interpretation is easiest when following a physical guide grid. Grids
can be laid out using chalk, paint, measuring tapes, ropes, or some other method. A grid can be any size,
but data quality is better if the grid corners are square. The grid itself does not have to be a square, it can
be a rectangle, or can be irregularly shaped.
Follow the tips below to help ensure successful grid setup and
data collection.
The graphic below illustrates how to put together a square,
10×10 grid. You can use the following method to setup grids of
any size including rectangular grids. Make sure to assign the
X and Y axis.
1
Locate the origin point (0,0) and pull a tape measure 10 units
to find the point 10,0 (blue line a). This is your baseline.
2
Pull one tape measure 10 units from (0,0) (green line
b) to (0,10).
3
Pull one tape measure from (10,0) to (0,10) (green
line c).
4
Move both green tapes together so that 10 on line b
connects to 14.14 on line c. The point that they
connect is the grid corner. You will know that the
corner at (0,0) is square because this method produces
a right triangle.
5
Repeat for the corner (10,10).
6
Once the grid corners are set you’ll need to mark the
starting and ending point of each line you’re going to
collect. You could either leave the baselines on the
ground or put markers, such as pin flags, along each
baseline. In the example to the right you would put a
flag at the beginning and the end of each orange
arrow.
7
Photograph or make a sketch map of the grid. Notes to include in the sketch map:
•
X and Y axis
•
Starting corner
•
Direction of the first and second line in each direction
•
Obstacles located within the grid
•
Location of trees inside and outside of the grid
•
Features that are visible on the ground surface