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muccc / iridium-toolkit

A set of tools to parse Iridium frames
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Position of IRA #80

Closed tk240 closed 2 years ago

tk240 commented 2 years ago

Output of IRA signals pos=(+49.51/+029.99) (I assume it is in decimal degrees, please tell me if not). The position information is printed with only two decimals after '.' . Is it rounded in the software? I wonder how many decmals possible to reach? Is it possible to get 5 decimal aftter '.' ?

Sec42 commented 2 years ago

The position transmitted by the satellites is in the xyz= info. This is in the ECEF coordinate system with 4km granularity in all three axis. So no, there is not enough precision available for 5 decimals.

The lat/lon value in this line is only a quick approximation for convenience, see bitsparser.py#L1385.

For a more exact conversion check Geographic_coordinate_conversion, for example via the pyproj library as used in locator.py.

tk240 commented 2 years ago

Does this mean that the position may have +-4km error for each axis?