← Back to context

Comment by delamon

11 hours ago

This blog post is also worth noting: https://ciechanow.ski/gps/

Yup, it was also posted in the other thread on GPS the other day and it is quite a bit better than OP's article, particularly because it doesn't give a false account of the involved relativistic effects:

> Satellites at the GPS altitude travel at the speed of about 2.4 mi/s relative to Earth, which slows the clock down, but they’re also in weaker gravity which causes the clock to run faster. The latter effect is stronger which in total results in a gain of around 4.4647 × 10−10 seconds per second, or around 38 microseconds a day.

> Unfortunately, this is where many sources make a mistake with their interpretation of that result. It’s often erroneously claimed that if GPS didn’t correct for these relativistic effects by slowing down the clocks on satellites, the system would increase its error by around 7.2 mi per day as this is the distance that light travels in those 38 microseconds.

> Those assertions are not true. If relativistic effects weren’t accounted for and we let the clocks on satellites drift, the pseudoranges would indeed increase by that amount every day. However, as we’ve seen, an incorrect clock offset doesn’t prevent us from calculating the correct position.

(Nevertheless there are of course relativistic effects to account for, which Ciechanow proceeds to mention and which are explained in more detail in the other link I shared here: https://news.ycombinator.com/item?id=47861535 )

> This blog post is also worth noting: https://ciechanow.ski/gps/

The author does note that:

> If you want to go much deeper, Bartosz Ciechanowski's interactive explainer on GPS is the gold standard. It covers signal modulation, orbital mechanics, and receiver architecture in far more detail than we do here.

Ciechanowski does a much better job explaining, I suspect the OP is just an AI ripoff.

  • You don't need to belittle someone else's work. It's a series of articles, and author has 2 more articles that aren't related to articles Ciechanowski wrote at all.