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Predict is a partial PHP port of theGpredict programthat allows real-time tracking and orbit prediction of satellites from two lineelement sets. It supports the SGP4 and SDP4models for prediction.

Just clone this repo and try out the tests and examples from the root of the checkout.

The tests directory includes a port of the original sgpsdp test files fromGpredict. They are pretty close.

Included in the examples directory is a sample iss.tle (with an update script, which youshould run first). There are two examples, the visible_passes.php script and the benchmark.phpscript. The former is for generating visible pass predictions of the ISS, and its output issimilar to what you might get from the Heavens-Above website, and it is heavily commented.The latter just does predictions for benchmarking with xhprof.

You can see an image of a Predict/Google Maps API mash-up I did for fun:

You can also see an example visible pass plotted from the polar view of the observer:

This port largely maintains the style and organization of the original C code, butscopes methods into classes rather than leaving everything in the global scope.The motivation for this is so that changes upstream can more easily be integrated overtime. Only the prediction routines have been ported.