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
Smith chart Smith chart points may be joined by straight lines to create a locus. A locus of points on a Smith chart covering a range of frequencies can be used to visually represent: The accuracy of the Smith chart is reduced for problems involving a large locus of impedances or admittances, although the scaling can be magnified for individual areas to accommodate these. A transmission line with a characteristic impedance of formula_2 may be universally considered to have a characteristic admittance of formula_3 where Any impedance, formula_5 expressed in ohms, may be normalised by dividing it by the characteristic impedance, so