Recent content by Cristiano

There is no doubt, but how to calculate x/y of the atmosphere (rotating frame) in the satellite reference frame (inertial frame)? I know that the atmosphere rotates with speed (with an adequate accuracy for me): Vrot= (6378.137 + alt_satellite) * (2 * PI) / 86162 * cos(lat_satellite) [km/s]...

Consider an artificial satellite orbiting the Earth and suppose that the atmosphere co-rotates with the Earth. I need to calculate x, y and z components of the atmospheric drag. I know how to calculate the drag in a non-spinning atmosphere and I have all the data to do that, but the Earth’s...

Please, would you post the formulas?

I use several web sites to search the visible passes of the ISS over a given location. Then I calculate the Sun elevation as seen from the ISS and I get surprisingly low elevations; for example, I get ISS magnitude= -3.8 and Sun elevation at the ISS= -19.9 deg. I suppose that the atmospheric...

I realize that my post is still unclear; here's what I'm currently doing. I have a black box with the input t (time in seconds) and the output y(t) (a real number). I only know that y(t) is very well fitted by an equation of the form: y(t)= k0 + k1 * sin(t * a1 + b1) + k2 * sin(t * a2 + b2) +...

That's only an example and I know how to find the parameters only when 0 ≤ t ≤ 2π. I need a working procedure to find the parameters in the equation: y(t)= k0 + k1 * sin(t * a1 + b1) + k2 * sin(t * a2 + b2) + ... knowing only y(t) and for any t (t is a time), not just for 0 ≤ t ≤ 2π. I guess...

Suppose that a parameter y= 123. That parameter is somehow "perturbed" and its instantaneous value is: y(t)= 123 + sin(t - 50°) * 9 + sin(t * 3 + 10°) * 3 + sin(t * 20 + 60°) * 4 Suppose that I don't know the above formula, but I can calculate y(t) for any t. Hence I decide to use the...

Probably I didn't get your point; let me try an example. Suppose that we have the vector g (ground speed) = 450 and the vector w (wind) = 50. The angle gt for g is 20° and the angle wt for w is 150°. The correct result is 150 - 20 = 130. I do: x= g * cos(gt) + w * cos(wt) y= g * sin(gt) + w *...

I already do that by hand, but the problem is that I need to find a general procedure or an algorithm (few lines of C code). I need something like this: 1) calculate angle= (WD + 180) - GT 2) if angle > 360 then angle= angle - 180 3) if angle < 0 then angle ... 4) ... but it's just an example...

This is a question about the well known trigonometric problem of the wind triangle, but my problem is just the calculation of the head wind component. I don't know how to write a general procedure to find the angle between the wind and the speed of the aircraft (the so called ground speed)...

I'll calculate a test statistics for some statistical tests (K-S, A-D, ...): http://www.itl.nist.gov/div898/handbook/eda/section3/eda35g.htm and then I'll compare that statistics with the critical values obtained from the current simulation to get the corresponding p-value (I interpolate the...

Please, would you elaborate a bit those two points? No, is just to improve the program efficiency, but it is totally OT here. My question is very easy; I need to do what I asked in my first post. Rephrasing a bit: I have many real random numbers with unknown distribution and I need to...

If I use only 100,000 numbers how can I calculate the quantile 10^-7? There are no bins in my procedure. I sort 10^8 numbers to calculate the quantiles of interest. What do you mean? I calculate 3 parameters simultaneously and my program is multi-threaded, hence I need 8 x 10^8 bytes for 1...

I don't know the exact definition, but I mean something like this: https://software.intel.com/en-us/node/497936 The program would be terribly slow; all the data must reside in RAM. I prefer a "small" but reasonably good number of random numbers in RAM.

If we consider that I calculate thousands of values for each quantile (to calculate its mean) and that each quantile is obtained from 108 random numbers, I'd say that the result is only reasonably accurate; I get only 2 or 3 significant digits for the extreme quantiles and 4 or 5 for the other...