BS ISO 06420:2016 pdf download.Hydrometry — Position fixing equipment for hydrometric boats
1 Scope
This document specifies methods of determining the position of hydrometric boats based on satellite navigation systems and/or with respect to known points on the banks of rivers, estuaries or lakes. It applies to electronic positioning equipment and conventional surveying techniques.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 748, Hydrometry — Measurement of liquid flow in open channels using current-meters or floats
3 Terms and definitions
For the purpose of this document, the terms and definitions given in ISO 772 apply.
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4 Requirements for position fixing
The necessity of using position fixing equipment arises in two types of measurements on open channels or lakes, reservoirs and estuaries. First, it is necessary to position a boat on a measuring section in order to conduct the appropriate observations of velocity and depth for a discharge measurement (as specified in ISO 748). The use of acoustic Doppler current profilers for making discharge measurements (see ISO/TR 24578) has largely diminished the need for position fixing equipment for hydrometric boats when making discharge measurements. However, there are still some types of measurements when verticals on a cross section have to be positioned for velocity and depth determinations. Position fixing also is required for collecting suspended sediment and bedload samples at appropriate verticals. The second type of measurements requiring position fixing are morphological surveys of lakes, reservoirs and estuaries. Position fixing is required to determine the positions at which depth observations and bottom samples are obtained.
5 Position fixing equipment for streamgauging and sediment sampling
5.1 General
There are different types of position-fixing equipment. This clause describes the following: measuring tapes, tag lines, global navigation satellite systems (GNSS), a combination of targets and electronic distance measuring equipment, electronic surveying equipment, and theodolites and stadia rods.
5.2 Tapes and tag lines
Tapes and tag lines are the most frequently used means for width measurements when measuring rivers by boat or wading. Steel measuring tapes with markings at metres and 10 ths of metres (or 100 ths of meters) are used in streams and rivers less than 50 m wide. A typical tag line consists of a marked corrosion-resistant steel cable that is 2 mm to 3 mm in diameter. The diameter of the tag line depends on the width of the channel, the velocity of the water and whether or not the same tag line is used for holding the boat and for determining its position. Larger diameter tag lines may be needed if used for dual purposes. Tag lines are typically marked at intervals of 5 m to 10 m with double markings at 50 m and 100 m. Tag lines are commonly used on channels up to 300 m wide, however, the accuracy of the distance measurements depends on cable tension. Long tag lines are usually wound on a drum having a diameter of at least 0,3 m and equipped with a cranking and braking mechanism. Caution should be used when tapes and tag lines are used to position hydrometric boats on navigable rivers. An observer on the river bank should be available to alert the hydrographers of approaching boats and also alert boat operators of the tape or tag line. Other operators may be required to temporarily remove the tape or tag line to allow boat passage through the measuring section.
BS ISO 06420:2016 pdf download
