Methods of Surveying Vegetation. 229 
for very detailed work restricted to small parcels of ground and 
giving results correct to 6 inches or even less. 
The Method of Squares. 
The basis of this method is the fact that a square pegged out 
on the ground can, with a little practice, be quickly and accurately 
mapped upon ruled sectional paper. A small square is of course 
easier to map than a large square, but it is well to avoid choosing 
too small a unit if the survey is to make reasonable progress. We 
found in the work referred to that a square with a side of 100 feet 
held the balance pretty evenly between accuracy and dispatch and 
consequentiy adopted it as the unit. 
To cover the ground to be surveyed with a continuous system 
of 100-foot squares, the following procedure is convenient 
A suitable base line (= line oc) is selected as in the case of an 
ordinary land survey. It is chained and posts planted every 
100 feet. The starting point of the base line is known as 
station 0, the 800-foot point as station 8, and so on. From certain 
selected stations on the base line perpendiculars are ranged with a 
theodolite on either side. These are chained and posts planted at 
100-ft. intervals. The stations on the perpendiculars may be con¬ 
veniently known as a, b, c, &c., in the direction above the base line, 
and z, y, x, &c., in the direction beloiv the base line. In the diagram 
{Fig. 77) perpendiculars have been raised at stations 5, 13 and 21 
and are termed the lines 5, 13 and 21. On the other hand 
parallels to the base line ranged through an, bb, &c., are distin- 
Fig. 77. Illustrates the various operations required to cover an area with a 
system of squares having 100-foot sides (see text). 
