czml path

CesiumJS
1

Hi,

in the simple czml there is "leadTime":

"leadTime":[
  {
    "interval":"2012-03-15T10:00:00Z/2012-03-15T10:44:56.1031157730031Z",
    "epoch":"2012-03-15T10:00:00Z",
    "number":[
      0,5537.546684141998,
      5537.546684141998,0
    ]
  }

What is the number property stands for?
I saw somewhere that it is seconds but then I have calculated the diff in secode between 2012-03-15T10:44:56.1031157730031Z and 2012-03-15T10:00:00Z, and the result is different from 0,5537.546684141998.

Thanks
Gad

2

From the specification:

https://github.com/AnalyticalGraphicsInc/czml-writer/wiki/Path

Lead time is the time ahead of the animation time, in seconds, to show the path.

In your example the value is specified as a sampled property with two samples, so the lead time value starts at 5537 seconds and linearly interpolates to zero.

The intent here is to show a single pass of the satellite’s orbit. So the value in this case is determined by the period of the orbit.

3

I am sorry but I still don't understand.
How does it determined by the period of the orbit?

4

The satellite in the file that contains the data you copied is the ISS, which has an orbital period of roughly 92 minutes, or approximately 5520 seconds. The data in this file was calculated from real TLE information in 2012 using STK.