摘要
投影日晷是起源於赤道日晷，由不同投影方向將赤道日晷上24 個小時點與晷針軸線投影到一平面所構成的日晷。晷面上小時點分佈和赤緯尺（晷針軸線投影）長短與緯度、投影角度與晷面傾角三者有關。投影日晷晷針外形主要為一條平行於投影方向的直線（即晷針線），此晷針線需隨著日期在赤緯尺上移動，投影日晷晷面上沒有固定的小時線，讀取日晷時是以固定的小時點為參考來判斷。由於投影日晷起源於赤道日晷，因此也會有時差問題，需要做時間修正才能轉成鐘錶時間。本文主要目的是利用個人設計的投影日晷程式展示投影日晷相關原理。使用者可透過改變程式中的緯度、晷面傾角與投影角度等參數，模擬不同視角的投影日晷，與不同日期時間、經度的晷針線影在晷面變化情形，以建構與深化空間與時間概念。
並列摘要
Analemmatic sundial is originated in equatorial sundial, that is, 24-hour points and gnomon of equatorial sundial are projected onto a plane by a selected projection angle. The distribution of hour points and length of scale of dates (from gnomon projection) are affected by latitude, the projection angle and the inclination of the dial plane. The gnomon of analemmatic sundial is parallel to the projection direction. There are no hour lines on the dial and the time of day is read by referring to the fixed hour points. The gnomon is not fixed and must change position daily to accurately indicate time of day. Local standard time can be obtained by applying the time corrections to sundial time.The main purpose of this paper was to show how to use my sundial program to demonstrate the principles of analemmatic sundial. By changing parameters such as the latitude, projection angle, inclination of the dial plane and 3D projection parameters, the program will simulate different projections of sundial. The program also simulates the shadow change according to different date/time and longitude. Hopefully, users can use this program to promote their concept of space and time.