ADD: new track message, Entity class and Position class

libs/geographiclib/wrapper/c/CMakeLists.txt

@@ -0,0 +1,39 @@
+cmake_minimum_required (VERSION 3.13.0)
+project (geoidtest)
+
+# Set a default build type for single-configuration cmake generators if
+# no build type is set.
+if (NOT CMAKE_CONFIGURATION_TYPES AND NOT CMAKE_BUILD_TYPE)
+  set (CMAKE_BUILD_TYPE Release)
+endif ()
+
+# Make the compiler more picky.
+if (MSVC)
+  string (REGEX REPLACE "/W[0-4]" "" CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS}")
+  set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} /W4")
+  string (REGEX REPLACE "/W[0-4]" "" CMAKE_C_FLAGS "${CMAKE_C_FLAGS}")
+  set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} /W4")
+else ()
+  set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wextra")
+  set (CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall -Wextra")
+endif ()
+
+find_package (GeographicLib REQUIRED COMPONENTS SHARED)
+
+add_executable (${PROJECT_NAME} ${PROJECT_NAME}.c cgeoid.cpp)
+target_link_libraries (${PROJECT_NAME} ${GeographicLib_LIBRARIES})
+
+get_target_property (GEOGRAPHICLIB_LIB_TYPE ${GeographicLib_LIBRARIES} TYPE)
+if (GEOGRAPHICLIB_LIB_TYPE STREQUAL "SHARED_LIBRARY")
+  if (WIN32)
+    add_custom_command (TARGET ${PROJECT_NAME} POST_BUILD
+      COMMAND
+        ${CMAKE_COMMAND} -E
+        copy $<TARGET_FILE:${GeographicLib_LIBRARIES}> ${CMAKE_CFG_INTDIR}
+      COMMENT "Installing shared library in build tree")
+  else ()
+    # Set the run time path for shared libraries for non-Windows machines.
+    set_target_properties (${PROJECT_NAME}
+      PROPERTIES INSTALL_RPATH_USE_LINK_PATH TRUE)
+  endif ()
+endif ()

libs/geographiclib/wrapper/c/README.md

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+# Calling the GeographicLib C++ library from C
+
+The geodesic routines in GeographicLib have been implemented as a native
+C library.  See
+
+  https://geographiclib.sourceforge.io/C/doc/
+
+It is also possible to call the C++ version of GeographicLib directly
+from C and this directory contains a small example, which convert
+heights above the geoid to heights above the ellipsoid.  More
+information on calling C++ from C, see
+
+  https://isocpp.org/wiki/faq/mixing-c-and-cpp
+
+To build and install this interface, do
+```bash
+mkdir BUILD
+cd BUILD
+cmake ..
+make
+```
+This assumes that you have installed GeographicLib somewhere that cmake
+can find it.  If you want just to use the version of GeographicLib that
+you have built in the top-level BUILD directory, include, e.g.,
+```bash
+-D GeographicLib_DIR=../../BUILD
+```
+
+in the invocation of cmake (the directory is relative to the source
+directory, wrapper/C).  To convert 20m above the geoid at 42N 75W to a
+height above the ellipsoid, use
+```bash
+$ echo 42 -75 20 | ./geoidtest
+-10.672
+```
+
+Notes:
+
+* The geoid data (`egm2008-1`) should be installed somewhere that
+  GeographicLib knows about.
+
+* This prescription applies to Linux machines.  Similar steps can be
+  used on Windows and MacOSX machines.
+
+* It is essential that the application be linked with the C++ compiler,
+  so that the C++ runtime library is included.
+
+* In this example, the main program is compiled with the C compiler.  In
+  more complicated situations, it may be necessary to use the C++
+  compiler.  This is necessary to get static initializations of C++
+  classes performed.  (However, GeographicLib doesn't need any static
+  initialization.)

libs/geographiclib/wrapper/c/cgeoid.cpp

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+#include "cgeoid.h"
+#include "GeographicLib/Geoid.hpp"
+
+extern "C"
+double HeightAboveEllipsoid(double lat, double lon, double h) {
+  try {
+    // Declare static so that g is only constructed once
+    static const GeographicLib::Geoid g("egm2008-1");
+    return h + GeographicLib::Geoid::GEOIDTOELLIPSOID * g(lat, lon);
+  }
+  catch (...) {
+    return GeographicLib::Math::NaN();
+  }
+}

libs/geographiclib/wrapper/c/cgeoid.h

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+#if !defined(CGEOID_H)
+#define CGEOID_H 1
+
+#if defined(__cplusplus)
+extern "C"
+#endif
+double HeightAboveEllipsoid(double lat, double lon, double h);
+
+#endif  /* CGEOID_H */

libs/geographiclib/wrapper/c/geoidtest.c

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+#include <stdio.h>
+#include "cgeoid.h"
+
+#if defined(_MSC_VER)
+/* Squelch warnings about scanf */
+#  pragma warning (disable: 4996)
+#endif
+
+int main() {
+  double lat, lon, h;
+  while(scanf("%lf %lf %lf", &lat, &lon, &h) == 3)
+    printf("%.3f\n", HeightAboveEllipsoid(lat, lon, h));
+}