diff --git a/include/sta/models/constants.hpp b/include/sta/models/constants.hpp
index b7b15c0..71b7f4b 100644
--- a/include/sta/models/constants.hpp
+++ b/include/sta/models/constants.hpp
@@ -5,8 +5,10 @@
 
 #define STA_CONSTANT_R 8.3144598 //J/(mol*K)
 
-#define STA_CONSTANT_G_0 9.80665 //m/s^2
+#define STA_CONSTANT_G_0 		9.80665 //m/s^2
+#define STA_CONSTANT_G_10KM		9.77593 //m/s^2
+#define STA_CONSTANT_G_20KM		9.74536 //m/s^2
 
 #define STA_CONSTANT_M 0.028964425278793993 //kg/mol
 
-#endif //STA_MODELS_CONSTANTS_HPP
\ No newline at end of file
+#endif //STA_MODELS_CONSTANTS_HPP