I purchased this ALTIMU-10 v5 which as of now I have hooked up to an arduino uno correctly. I would like to accurate readings from ground level pressure to be approximately zero, and to be able to read up to about 15 ft in height.
At ground level I am obtaining this from the serial monitor (utilizing sample code given in your website) " p: 30.26 inHg a: -310.25 ft t: 75.19 deg F"
I estimated the pressure at 15 ft from that point to be around 30.25642880002076 inHg
How do I properly calibrate the sensor to read zero ft at the 30.26 inHg?
The simplest approach that would probably give acceptable results is to take an initial pressure reading when your program starts, convert it to an altitude estimation to use as an offset, and subtract that offset from subsequent altitude calculations. For example, after getting the values you posted, your program could then subtract -310.25 ft from (or add 310.25 ft to) the calculated altitude from then on.
Alternatively, you could provide the pressureToAltitudeFeet() function with an accurate altimeter setting so that it can compensate for the actual regional pressure and give a more accurate absolute altitude; for more information, read the description of pressureToAltitudeMeters() in the library reference. Then you could subtract your actual ground level altitude from the calculated altitude to get the height above the ground. However, I would expect the reliability of this method to be very dependent on how accurate the altimeter setting value is, and it would require you to always update your altimeter setting and ground level altitude for your location and time. If you only care about relative height above ground level, subtracting an offset like I described above is probably the best method.
