How do I calculate a xyz-position of a GPS-position relative to an other GPS-position?

I have high-precision and fairly high-accuracy GPS position data for a person walking, and I wish to derive the heading at each data point.  My data are discrete time x and y values. The trivial answer is to calculate the vector from each x,y position...

Seems that no matter how perfectly positioned these GPS satellites are they would drift out of position and that would throw off the computations of our GPS units in cars etc.

now days smart phone comes with loaded gps..if i buy 1..and use it for driving ..will it show position when i drive like a normal gps driving reciever or will it doesnt move unless i manualy update my position time to time?

I don't know why my app's GPS accuracy is lower than BingMap. I use GeoLocator and set the accuracyinmeters to 1. And I also try to set the accuracy to high. But the result is about 500 meters from where I actually am. I also try the BingMap's app, and...

I have been reading a book called Fun with GPS which mentions differences in the models being used (in 2005 and earlier) and it suddenly occurred to me that the mention of computing power varying might lead to an interesting experiment - which we might...

If I had to guess, it would be 10,000 miles.  I have no reason or evidence for this. What causes a spacecraft to vary from its planned position?

You can easily calculate the position of the sun in the sky, given lat, lon, time, and elevation.  Yet, PV tracker systems commonly use GPS systems for attitude control.  Why use a GPS-based control system at a fixed location?

The drivers of my company want to know how does a GPS tracking unit calculate speed and how accurate is it.