Measuring along the ground:
The most accurate way to measure distance with a steel band is to measure the distance between pre-set measuring marks, rather than attempt to mark the end of each tape length. The procedure is as follows:
(1) The survey points to be measured are defined by nails in pegs and should be set flush with the ground surface. Ranging rods are then set behind each peg, in the line of measurement.
(2) Using a linen tape, arrows are aligned between the two points at intervals less than a tape length. Measuring plates are then set firmly in the ground at these points, with their measuring edge normal to the direction of taping.
(3) The steel band is then carefully laid out, in a straight line between the survey point and the first plate. One end of the tape is firmly anchored, whilst tension is slowly applied at the other end. At the exact instant of standard tension, both ends of the tape are read simultaneously against the survey station point and the measuring plate edge respectively, on command from the person applying the tension. The tension is eased and the whole process repeated at least four times or until a good set of results is obtained.
(4) When reading the tape, the metres, decimetres and centimetres should be noted as the tension is being applied; thus on the command ‘to read’, only the millimetres are required.
(5) The readings are noted by the booker and quickly subtracted from each other to give the length of the measured bay.
(6) In addition to ‘rear’ and ‘fore’ readings, the tape temperature is recorded, the value of the applied tension, which may in some instances be greater than standard, and the slope or difference in level of the tape ends are also recorded.
(7) This method requires a survey party of five; one to anchor the tape end, one to apply tension, two observers to read the tape and one booker.
(8) The process is repeated for each bay of the line being measured, care being taken not to move the first measuring plate, which is the start of the second bay, and so on.
(9) The data may be booked as follows