Interplanetary magnetic field (IMF) sector structures, such as 'toward' the sun and 'away' from the sun on each day, have been objectivly estimated from daily and monthly mean values of the horizontal component of the geomagnetic variation field at Godhavn during the period 1926--1970. The agreement between this estimation and actual satellite observations of the sector structures of the interval 1964--1970 is 88, 79, and 58% in summer, equinox, and winter, respectively. A remarkable agreement (more than 95%) is obtained for the summers of 1964, 1969, and 1970. Various types of IMF sector behavior are examined by taking this seasonal factor into consideration. Approximately 27-day recurrences of the same structure are often found, and 5- to 14-day consecutive occurrences of the same sector are frequently noted. Furthermore, the total number of occurrences for each estimated sector in each year shows an apparently good correlation with smoothed sunspot numbers and geomagnetic aa index. After a brief introduction of the production mechanism of sector effects on polar geomagnetic fields the limitations and merits of IMF sector inference from geomagnetic data are emphasized.