Construction

It is a band of cloth, reinforced cloth, plastic or steel about 1.5 cm wideand of varying length and is used to measure girth of trees and logs. It is usually graduated one side in cm and mm but sometimes it is graduated on both sides to give measurements in metric system on one side and those in British system on the other. The ends of the tape are always plated some metal to prevent their tearing off but in case of longer tapes which are kept encased in some cover by winding it in or in some other cases too, the beginning of tape has a metal ring to hold it.

In western countries, tapes are often provided with hook enables one person to measure large trees with tapes lying flat in correct position on the tree.

Types

1. Cloth Tape: The tapes are made of cloth, though they may be paintedwith some paint on both sides to give better look and correct them from the influence of water. They are alsoaffected by fluctuations in length due to expansion in use.
2. Metallic Tape: The better quality of tapes are usually reinforced inside by metal wires and are, therefore called metallic tapes. They are painted with some durable paint. So, they are more durable and reliable.
3. Steel Tape: Steel tapes are used for precise work and are mostly used in forest for measurement in sample or research work.

In western countries nylon coated steel tapes and fiberglass tapes are available.

The tree measuring tapes are generally 3 m long or at the most 5 m. But land measurement tapes may be 5m, 10m, 30m or even 50 m long. In British measures, these tapes are usually 25ft, 50ft and 100ft long. Such long tapes are generally cased in some leather or plastic case with some winding arrangement so that they are secure inside the case when not in use. The tree measuring tapes, which are usually small, do not generally have cases to cover them, though some steel tapes are 2 or 3 m long are kept in cases with some spring device to wind them back when not in use.

Though trees are meant for girth measurement, some of them are so graduated as to read diameter instead of girth. As girth is equal to πd, the tape is calliberated as per the formula.

Advantages

• Tape is convenient to carry
• It does not require constant adjustment
• Only one measurement is needed even with irregular trees
• In case of logs lying on ground, it is not possible to measure two diameters at right angles to each other by callipersand diameter measurement by the tape is easiest
• The error in case of tape are always positive and systematic and so if any adjustment by tape is needed, it can be done easily
• Tape negotiates the whole circumference of the tree while calliperstouch only three points on it. So a tape measures the size of the tree better than callipers

Disadvantages

• If the tree has rough bark, the tape exaggerates the diameter or girth measurement.
• It is somewhat slower to use particularly in areas with dense shrub growth
• The observer doesn’t see the full circumference of the tree and has no knowledge of presence of knots or swellings which may affect the diameter of girth measurement
• As the tape has to be swung round the tree it is frequently not applied to in a plane right angles to the axis of the tree
• Differences in tension of the tape due to elastically affects true diameter or girth measurement

Uses of Tape

• To measure girth and diameter of the trees
• To measure length of seedlings, saplings, shrubs, deadwood, etc
• To measure distance from the base of trees to the point of measurement especially in case of vertex

Causes of Errors by Tape

• Displacement of the tape from the horizontal
• Elasticity of tape
• Expansion of tape

Precautions

• The tape should not be old and therefore stretched or possibly with the end broken off.
• It must be flat against the tree and not in twisted manner
• It must lie in a plane perpendicular to the axis of tree so that the girth and consequently the basal area is over estimated.
• After swinging the loose end of the tape round thetree, care should be taken to see that no climber or branch of nearby shrub has vitiated the girth measurement. If so they should be cut out before swinging the loose end of the tape round the tree
• The tape should be taken care of wet and twisted