A paper I did for uni back in 2013
On 2 April, 2013, a plane survey was conducted of a mixed species rainforest plantation on private property at Wollongbar, northern New South Wales. The plane survey was undertaken by walking around the perimeter of the plantation and taking measurements from one survey point tree to the next tree using a variety of instruments. The data was then taken back to a computer laboratory at Southern Cross University, entered and analysed. A conclusion was derived that it is an accurate and precise method to measure the perimeter of a forest stand, but is dependent upon observational acuity and familiarity with the instruments.
The aim of the plane survey was to accurately assess the external boundaries of the plantation and to familiarise students with the concepts of a plane survey, and in the usage of measuring instruments and recording and calculating methods. Previous surveys have been conducted at this location and the scientific environment is fairly well established. The plane survey is so named as the mapping is represented on a flat piece of paper, the plane (West, 2009).
The survey was performed on private property, “Pamplemousse Park”, located in a rural area in Wollongbar, a town approximately 13 kilometres east of the regional centre Lismore, in northern New South Wales .
The plantation was on sloped terrain, with the slope generally ascending toward the northwest. The soils appear to be of the Ferrosol variety, although no analysis was performed. Two separate tracks sub-divided the plantation into three unequal sections. A variety of sub-tropical rainforest species have been planted including Elaeocarpus grandis, Agathis robusta, Podocarpus elatus, Araucaria bidwilli, A. cunninghamii, Syzygium moorei and Argyrodendron trifoliolatum. There was a considerable amount of saprophytic fungi present amongst the ground litter, predominantly of the shelf fungi variety though there were some jelly fungi present on log and branch detritus.
The plantation has an irregular shape, and is surrounded by tracts of macadamia trees growing in orchards, with the species either Macadamia tetraphylla or M. integrifolia which are the two commercially raised for their nuts in Australia. These tracts are not a part of the plantation and do not figure any further in this report.
The students were divided into three groups. Each group, numbering from three to four members, were given a prismatic compass, a clinometer and a 100 metre measuring tape. Results were recorded on a printed pro forma. The boundary of the plantation was determined by choosing trees that were on the periphery and were clearly on the apex of a bend or at an equidistant point between two such apices. From tree to tree, the distance between was measured, and the bearing in degrees (from north) was recorded. The slope angle between the trees was measured and this was achieved by using the clinometer at the measuring tree and taking a reading of the foot of the target tree, with consideration given to the height of the measurement-taker. At each successive tree, a back bearing was recorded to the previous tree, which under ideal situations would be 180 degrees but this was not often the case in real conditions. Where the survey intersected the tracks, the points were taken from the corners of the tracks (Southern Cross University, 2013). The area within the tracks was not counted for statistical purposes .
Only live trees were considered when establishing the boundary. Dead trees on the periphery and other non-tree flora were not counted. These were surveyed around and only the actual planted area was counted (Southern Cross University, 2013). Once the initial perimeter was surveyed, the two tracks within the plantation were measured for length, width and slope angle.
In the university laboratory, the results were collated and entered into Microsoft Excel. The data were tabulated into fields thusly: survey point, forward bearing, back bearing, slope angle, and slope distance. From these data a variety of means and distances were obtained using established mensuration formulae (West, 2009).
In the laboratory, the data were analysed using a variety of published formulae (West, 2009). Microsoft Excel was used to perform all calculations and analyses and a map was constructed using the in-built scatter plot function. Figure 1 shows the derived map.
Figure 1. Map of the plantation derived from the plane survey
Each of the plotted points in the figure represent one surveyed tree. As can be seen, the beginning and end points do not intersect. There was an observational error for part of the walk around survey in which one of the students misread the compass readings. This was later amended both in situ and in the laboratory. Even with these corrections, there is still a reasonably sized error. The method used to survey the perimeter has an innate and variable lack of precision due to human error, greater than using more sophisticated methods such as laser rangefinders, global positioning systems and theodolites. However, it has been suggested that where a highly precise map is not required, the usage of handheld compasses and clinometers, etc, is acceptable (West, 2009).
The lack of precision was most obvious with the results found for the closing distance and close error. The end result for the plane survey was an error of 14 metres in 628.5 metres measured. This can be represented as being one metre away from the true figure for every 44.8 metres measured. This figure has been derived by using a formula that can be found on page 130 of Tree and Forest Measurement, 2nd Edition, by West. Future surveys would be expected to be undertaken with a greater deal of precision due to the increased familiarity with the techniques and the instruments used. Continual cross-checking for errors as the survey was being walked would also be useful.
The plane survey method to measure the perimeter of a forest stand generally gives a precise and true reckoning, however this is dependent upon observational skill and the instruments used. In the case with the plantation at Pamplemousse Park, there was a mostly accurate reading, and the fundamental principles of the plane survey were both understood in regards to utility and calculation. Further practice is required to achieve more accurate results.
Southern Cross University (2013). Practical exercise 1: Plane survey. (Lecture notes).
West, P.W. (2009). Tree and Forest Measurement (2nd ed.). Berlin, Germany: Springer-Verlag