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The mapping of the apple trees

 
The apple trees were mapped by the classes VT03 – VT06, who determined their location by tying them into a baseline.

How to tie objects into a baseline

 
In some respects tying-into a baseline is similar to a coordinate system, but uses only one axis rather than two. That one axis is called a “baseline”. The location of a baseline can be determined in one of three ways:

- It can be established on the basis of a known line.

- It can be established on the basis of two known points.

      - It can be established arbitrarily.

In the final analysis it really makes no difference which method is used, although the first two have the advantage of being replicable; later fieldworkers can come in and replicate or check the notes. Baselines can be "staked" with ranging-poles which can be written on if quasi-permanent and accurate mapping is needed, or with chaining pins.The tail of a tape measure is then held at one end of the baseline which can be considered a datum, and the head of the tape is taken to the point perpendicular to the first object to be tied-in. This latter point can be determined with some accuracy by means of a devise known as a right-angle prism.The distance you measure from the baseline to the object is called “offset”. The process is then repeated until each object is tied-in. Distances along the baseline are recorded in two ways:

- Relatively (from one point to the next)

- In terms of stations