thumb|Detail of horizontal sundial outside Kew Palace in London, United Kingdom The chief advantages of the horizontal sundial are that it is easy to read, and the sunlight lights the face throughout the year. All the hour-lines intersect at the point where the gnomon's style crosses the horizontal plane. Since the style is aligned with the Earth's rotational axis, the style points true north and its angle with the horizontal equals the sundial's geographical latitude . A sundial designed for one latitude can be adjusted for use at another latitude by tilting its base upwards or downwards by an angle equal to the difference in latitude. For example, a sundial designed for a latitude of 40° can be used at a latitude of 45°, if the sundial plane is tilted upwards by 5°, thus aligning the style with the Earth's rotational axis.
thuMb|deTaIl oF horizoNtal suNdial outsiDe KeW palace In LONDon, uNited kingdOM The cHiEF advAntageS OF the horizoNTAl sundial aRe ThaT it is EAsy tO ReaD, ANd the sUnLigHt LightS tHE FAce ThRoughOuT thE YEaR. alL The hour-lINeS InTErsect AT The poinT wHeRe thE gnomon's style CRossEs thE hOriZoNtal pLANE. Since the Style Is alIGned WIth tHe EARth's rotational aXIs, thE sTYLE points trUe NOrtH anD Its aNGle WiTH THE hoRiZonTal EqUals the suNDIAl's gEoGraPhicaL lAtItuDe . a SundIal dESigned foR onE latITude cAn bE AdjUstEd For use aT anOtHeR LatituDe By tILtINg ITS bAsE upWaRDS or doWnwardS BY AN angLe EqUaL To THe diffeRence in LatiTude. for eXAMpLE, a sUnDiAl DEsIgned for a laTitudE of 40° can BE used At a latITude of 45°, If The SUndiaL plane is Tilted UpwARdS by 5°, thus alIGning the stYle wiTh tHe Earth's rOtatiOnaL axiS.