ASM, ICAO or TSA? The Standard Atmosphere was developed or chosen over time. Historically the research done around the world without the connectivity we have today, was based on different regional conditions and environments. In the modern world all the different environments were standardized and names assigned to each.
It is crucial to know which standard is used. When reporting a Mach number, one can realize the difference in result as there are 3 different speed of sound standard values that can be used. The same is applicable for all other standard values listed in this table.
ASM Army Standard Metro
ICAO International Civil Aviation Organization
TSA Traditional Standard Atmosphere
The following a listing to show the differences.
| ASM | ICAO | TSA | Unit | |
| Air Density | 1.2034 | 1.2251 | 1.205 | kg/m^3 |
| Air Temperature (T) | 15 | 15 | 15 | Celsius |
| Barometric pressure | 750 | 760 | 750 | mmHg |
| Speed of Sound | 341.458 | 340.3 | 340.83 | m/s |
| Relative Humidity RH% | 78% | 0 | 50 | % |
| Virtual Temperature | 289.6 | 288.15 | 289.08 | Kelvin |
The Standard Temperature for propellant for ASM and ICAO is 21 °C and 15 °C for TSA