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aholinch / sgp4

SGP4 implementations in multiple languages
The Unlicense
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[C language]Some questions about WGS72 and WGS84 #6

Open Revincxt opened 11 months ago

Revincxt commented 11 months ago

Hello, dear author, I have some questions I'd like to ask. In the C implementation part of your project, could you please explain the differences between WGS72 and WGS84 in the SGP4 code and why WGS72 is used in the code instead of WGS84?

aholinch commented 11 months ago

The constants are what were selected by the original authors. I am not the original author. I give credit to CSSI as the organization that published this code. However, their web links change from time-to-time. They explain their support for WGS72 and WGS84 in their paper Revisiting Spacetrack Report 3. Their purpose, and mine as well, is to focus on compatibility with the USAF (now USSF) standard implementation of SGP4. For most applications, I believe the difference between 72 and 84 will be much less than the difference between TEME and other coordinate systems. Another paper by those authors here has a section on converting between TEME and ITRF.

Revincxt commented 11 months ago

Okay, thank you for your answer. It's really helpful to me.