Surface weather analysis isotherms (lines of equal temperature), and isotachs (lines of equal wind speed) are drawn. The abstract weather symbols were devised to take up the least room possible on weather maps. A synoptic scale feature is one whose dimensions are large in scale, more than several hundred kilometers in length. Migratory pressure systems and frontal zones exist on this scale. Centers of surface high- and low-pressure areas that are found within closed isobars on a surface weather analysis are the absolute maxima and minima in the pressure field, and can tell a user in a glance what the general weather is
Equal pay for equal work effects, with trade unions sometimes promoting conservatism. However, following the Second World War, trade unions and the legislatures of industrialized countries gradually embraced the principle of equal pay for equal work; one example of this process is the UK's introduction of the Equal Pay Act 1970 in response both to the Treaty of Rome and the Ford sewing machinists strike of 1968. In recent years European trade unions have generally exerted pressure on states and employers for progress in this direction. In international human rights law, the statement on equal pay is the 1951 Equal Remuneration Convention, Convention 100 of