> p1 and p ranges: 100.000 hPa to 1200.000 hPa

You get floating point pressure values out of your pressure sensor?  (I
guess it's possible, especially if you're reading it from something like
a GPS "thing"...)

The point is that usually a pressure sensor is connected to an integer A-D
converter, and that it may make a lot more sense (performance-wise) to stay
in that integer domain as long as possible while you're doing your math,
especially since your end result is probably an integer as well (feet or
meters of altitude, right?)  Why convert your integer pressure reading to a
floating point number, plug it into a complex floating point equation, and
finally convert back to an interger readout when the PIC would rather not
do floating point?

That means manipulting the formula quite a lot, but makes things a lot
easier for the PIC.

BillW

--
http://www.piclist.com hint: The PICList is archived three different
ways.  See http://www.piclist.com/#archives for details.