<P> 8 - point compass roses use the eight principal winds--that is, the four cardinal directions (N, E, S, W) plus the four "intercardinal" or "ordinal directions" (NE, SE, SW, NW), at angles of difference of 45 ° . </P> <P> 16 - point compass roses are constructed by bisecting the angles of the principal winds to come up with intermediate compass points, known as half - winds, at angles of difference of 22 ⁄ ° . The names of the half - winds are simply combinations of the principal winds to either side, principal then ordinal . E.g. North - northeast (NNE), East - northeast (ENE), etc . </P> <P> 32 - point compass roses are constructed by bisecting these angles, and coming up with quarter - winds at 11 ⁄ ° angles of difference . Quarter - wind names are constructed with the names "X by Y", which can be read as "one quarter wind from X toward Y", where X is one of the eight principal winds and Y is one of the two adjacent cardinal directions . E.g. North - by - east (NbE) is one quarter wind from North towards East, Northeast - by - north (NEbN) is one quarter wind from Northeast toward North . Naming all 32 points on the rose is called "boxing the compass". </P> <P> The 32 - point rose has the uncomfortable number of 11 ⁄ ° between points, but is easily found by halving divisions and may have been easier for those not using a 360 ° circle . Using gradians, of which there are 400 in a circle, the sixteen - point rose will have twenty - five gradians per point . </P>

In figure a-24 what part does the letter a point to