elevation and azimuth calculation

[dreambox1959]

I have been using an excel spreadsheet for years that I created with a mathematician friend, it gives me good results for a polar mount.
I wanted to calculate for an AZ/EL mount like the EGIS engine, I found several calculation websites, formulas etc. none of them give the same result, it's close but on the extremes it's almost 5° different !!!.
I'm not sure if anyone has ever done this exercise before.
Give me your experience.

 

[g host]

Some years ago i found this: Calculation of Azimuth, Elevation and Polarization for non-horizontal aligned Antennas. Algorithm Description. Technical Document
and this: Calculating Antenna Bearings for Geostationary Satellites

 

[Channel Hopper]

I have been using an excel spreadsheet for years that I created with a mathematician friend, it gives me good results for a polar mount.
I wanted to calculate for an AZ/EL mount like the EGIS engine, I found several calculation websites, formulas etc. none of them give the same result, it's close but on the extremes it's almost 5° different !!!.
I'm not sure if anyone has ever done this exercise before.
Give me your experience.

Most errors will be down to true elevation of the earth station, and the equatorial GEO.

One moment, please...

There is always some tolerance though.

 

[dreambox1959]

I found a compromise thanks to the satlex.be website:
in the CSV file generated by this site there are several data :
the first azimuth calculation corresponds to a fixed parabola orientation or to the azimuth of an egis .
and in the polarmount column the values are almost all identical to my own calculations.
for these cases i have the mathematical equation .
for the elevation and skew I don't have !!! but satlex does !
for the egis :
knowing that there are 100 changes of state of the pulse per degree of azimuth it is easy to create the file for my posi from satlex (200 pulses per degree)
and for elevation it's double (400 pulses per degree)
This precision is insane because it is far superior to the mechanical game.

 

[dreambox1959]

I studied the formulas for azimuth and elevation calculations on the satlex.be website.
I managed to put it in an Excel table to calculate the az and EL index of the Egis EPR103 engine.
In my JPC-POSI program I have provided a function to set the value of the pulse counter in the LIMITS menu. This function allows you to readjust the whole system after a technical problem or power failure without having to search for everything.
The principle is to point to an easy satellite (Astra 19.2e) and to arbitrarily assign the value of the AZ pointer to the previously known value, so that everything is reset to the correct value.
This principle applied to the EGIS engine will allow to impose a table of values previously calculated by proceeding in the same way:
You point to Astra, you know that the precalculated value is 8000 in az and 5000 in EL (examples), you go to the LIMITS menu and you enter these values, by leaving this menu all the values of the eeprom will be very close to reality.
On the other hand the management of the points of origin (AZ and EL) is present in my software but this function will have to be reworked not to destroy the procedure described before.
In the case of EGIS there is a technical peculiarity: there are 200 pulses per degree in azimuth and 400 in elevation, a simple calculation allows to predict the difference of pulses between two satellites.
On the other hand an offset (different for each engine) exists in AZ and EL and it is by the procedure described that one can bypass it.
I have also planned to stop the motor control a few moments before reaching the destination, this is configurable in the LIMITS menu.

 

[dreambox1959]

FEMI gave me a list of their EGIS positioner data.
I put his data side by side with mine calculated from SATLEX, apart from a few extreme positions I get an average difference of about 0.10 degrees in azimuth and 0.08 degrees in elevation, which is very good.
Conclusion SATLEX calculations are interesting to use.
Here is a table where in column B there are the azimuth values and column I the elevation values taken by FEMI, in column C and J the calculated value in pulses (*200 azimuth x400 elevation).
In columns E and L my values calculated from SATLEX and in columns G and N the error in degrees.

 

[rodscha]

Good morning Dreambox!
I can t open your file..;
Have a good day!

 

[dreambox1959]

it s an excel file !
but you use openoffice with calc , it s free

 

[rodscha]

thank you,I managed to open it with Calc.
Have a good day!