1.添加了EGM96-5的数据集和算法支持，可以正确求解GEOID Offset高度。

2.在同步时间时现在会将起飞点的海拔高度写回到配置文件/home/data/Settings/MainSettings.ini键值为WBACK/HeightOfHomePoint
3.现在的高度回调函数以及获取函数调整为了DJI_FC_SUBSCRIPTION_TOPIC_ALTITUDE_FUSED。

Source/EGM96/EGM96.h

@@ -0,0 +1,39 @@
+/*
+ * Copyright (c) 2006 D.Ineiev <ineiev@yahoo.co.uk>
+ * Copyright (c) 2020 Emeric Grange <emeric.grange@gmail.com>
+ *
+ * This software is provided 'as-is', without any express or implied warranty.
+ * In no event will the authors be held liable for any damages arising from
+ * the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not
+ *    claim that you wrote the original software. If you use this software
+ *    in a product, an acknowledgment in the product documentation would be
+ *    appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *    misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
+ */
+
+#ifndef EGM96_H
+#define EGM96_H
+/* ************************************************************************** */
+#ifdef __cplusplus
+extern "C" {
+#endif
+/*!
+ * \brief Compute the geoid undulation from the EGM96 potential coefficient model, for a given latitude and longitude.
+ * \param latitude: Latitude (in degrees).
+ * \param longitude: Longitude (in degrees).
+ * \return The geoid undulation / altitude offset (in meters).
+ */
+double egm96_compute_altitude_offset(double latitude, double longitude);
+#ifdef __cplusplus
+}
+#endif
+/* ************************************************************************** */
+#endif // EGM96_H