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

With very long baselines, one cannot afford to go back to the beginning of your baseline and start over every time a feature is tied-in. The standard procedure in these cases is to place a stake or a chaining pin every 100 meters (or feet). These points are the stations. After measuring the distances along the baseline you have to record the distances of the offset.So every object gets coordinates and you have located its position.