GeolocationCoordinates：altitude 屬性
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GeolocationCoordinates 介面的 altitude 唯讀屬性是一個 double 值，表示位置相對於 WGS84 橢球（定義名義海平面）的高度（以公尺為單位）。如果實作無法提供此數據，則此值為 null。
值
一個 double，表示位置相對於 WGS84 橢球的高度（以公尺為單位）。
規範
| Specification |
|---|
| Geolocation # altitude-and-altitudeaccuracy-attributes |
瀏覽器相容性
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