Isaac Adjei

GPS works by trilateration from four satellites: three for position, one to correct clock error

Each GPS satellite broadcasts its precise position and a timestamp. Your receiver calculates the time delay between broadcast and reception and converts it to a distance. Three satellites give you three spheres; the intersection narrows to two points, one of which is obviously on Earth. But your receiver's clock is not as precise as an atomic clock, so its timing error translates directly to position error (light travels ~30 cm per nanosecond). The fourth satellite resolves this: by requiring all four distance estimates to intersect at one point, the receiver can solve for its own clock offset as a fourth unknown.

25 Jul 2026

`git rebase --onto` transplants a branch from one base to another

If you branch off a feature branch and then want to rebase your commits directly onto main, skipping the feature branch commits entirely, `git rebase --onto <newbase> <upstream> <branch>` is the command. It replays only the commits between `<upstream>` and `<branch>` on top of `<newbase>`, leaving everything before `<upstream>` behind.

23 Jul 2026

Python is compiled to bytecode before it runs: the `.pyc` files are the compiled output

CPython compiles your `.py` source to bytecode (`.pyc` in `__pycache__/`) on first import. This is not machine code: it is a sequence of opcodes for the CPython stack-based virtual machine. The VM interprets these opcodes one by one. This is why CPython is slower than compiled languages: every operation goes through the interpreter loop. Tools like [Cython](https://cython.org/), [Numba](https://numba.pydata.org/) and [PyPy](https://www.pypy.org/) bypass this by compiling to actual machine code.

21 Jul 2026