1 // Write the coefficient files needed for approximating the normal gravity
2 // field with a GravityModel. WARNING: this creates files, wgs84.egm.cof and
3 // grs80.egm.cof, in the current directory.
4
5 #include <cmath>
6 #include <fstream>
7 #include <iostream>
8 #include <GeographicLib/NormalGravity.hpp>
9 #include <GeographicLib/Utility.hpp>
10
11 using namespace std;
12 using namespace GeographicLib;
13
main()14 int main() {
15 try {
16 Utility::set_digits();
17 const char* filenames[] = {"wgs84.egm.cof", "grs80.egm.cof"};
18 const char* ids[] = {"WGS1984A", "GRS1980A"};
19 for (int grs80 = 0; grs80 < 2; ++grs80) {
20 ofstream file(filenames[grs80], ios::binary);
21 Utility::writearray<char, char, false>(file, ids[grs80], 8);
22 const int N = 20, M = 0,
23 cnum = (M + 1) * (2 * N - M + 2) / 2; // cnum = N + 1
24 vector<int> num(2);
25 num[0] = N; num[1] = M;
26 Utility::writearray<int, int, false>(file, num);
27 vector<Math::real> c(cnum, 0);
28 const NormalGravity& earth(grs80 ? NormalGravity::GRS80() :
29 NormalGravity::WGS84());
30 for (int n = 2; n <= N; n += 2)
31 c[n] = - earth.DynamicalFormFactor(n) / sqrt(Math::real(2*n + 1));
32 Utility::writearray<double, Math::real, false>(file, c);
33 num[0] = num[1] = -1;
34 Utility::writearray<int, int, false>(file, num);
35 }
36 }
37 catch (const exception& e) {
38 cerr << "Caught exception: " << e.what() << "\n";
39 return 1;
40 }
41 catch (...) {
42 cerr << "Caught unknown exception\n";
43 return 1;
44 }
45 }
46