Hello, I did this because I noticed that the altitude of GPS is not stable. GPS coordinates are correct however.
They remain well within a radius of ten meters around the real point. But the altitude is completely crazy, it depends on the day, and even the moment of day. This is related to the position of satellites, I am in Europe, Is this the problem?.But, it's may be a problem for the stabilization of our plane in altitude. And increasingly it is not very accurate.
And with two I2C devices it works, cool.
What do you think of this approach?
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arduimu.zip
http://ardunxt.googlecode.com/files/SCP1000_D11_release_1.zip
And then it is merged with the code Arduimu.
The idea of putting a filter is interesting, there are still small variation of the order of 10 to 20 centimeters. The test is done indoors and rest on the outside it might be otherwise.There is there a model to do?
No Darren, SA has been off for a number of years now. (it was > +/- 50 metres in X and Y when it was on).
Height is the most sensitive parameter from the triangulation process, simply because of the geometry of the sats.
The low elevation sats are particularly troublesome because they are most distorted by the longer path through the atmosphere/ionosphere and most susceptible to multipath reflections.
So if you can chop them out by increasing the min horizon mask, those sats will not corrupt the solution.
These low elevation satellites bias the solution most greatly in the Z component (height) so when one drops out, there is a corresponding "step" in the computed height.
This can be up to > 5m. Of course when the aircraft resumes staright and level, the sat is re-acquired and another step occurs.
The barometric aiding is a good solution that overcomes this problem, but most baro signals need to be heavily filtered to be usable for height control.
Another solution is to raise the horizon mask in the GPS setup to 15 deg which prevents usage of the lower (most innacurate) satellites.
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