Editing Altimeter (section)

===Global Positioning System===
[[Global Positioning System]] (GPS) receivers can also determine altitude by [[trilateration]] with four or more [[satellite]]s. In aircraft, altitude determined using autonomous GPS is not reliable enough to supersede the pressure altimeter without using some method of [[GNSS Augmentation|augmentation]].<ref name="Albéri2017">{{cite journal|last1=Albéri|first1=Matteo|last2=Baldoncini|first2=Marica|last3=Bottardi|first3=Carlo|last4=Chiarelli|first4=Enrico|last5=Fiorentini|first5=Giovanni|last6=Raptis|first6=Kassandra Giulia Cristina|last7=Realini|first7=Eugenio|last8=Reguzzoni|first8=Mirko|last9=Rossi|first9=Lorenzo|last10=Sampietro|first10=Daniele|last11=Strati|first11=Virginia|last12=Mantovani|first12=Fabio|title=Accuracy of Flight Altitude Measured with Low-Cost GNSS, Radar and Barometer Sensors: Implications for Airborne Radiometric Surveys|journal=Sensors|date=16 August 2017|volume=17|issue=8|pages=1889|doi=10.3390/s17081889|pmid=28813023|pmc=5579878|arxiv=1802.00327|bibcode=2017Senso..17.1889A|doi-access=free}}</ref> In hiking and climbing, it is common to find that the altitude measured by GPS is off by as much as {{convert|400|ft|m|0|abbr=off}} depending on satellite orientation.<ref name="Garmin support">{{cite web|url=https://support.garmin.com/en-US/?faq=QPc5x3ZFUv1QyoxITW2vZ6|title=Understanding the Accuracy of the GPS Elevation Reading|website=Garmin|access-date=March 14, 2020|archive-url=https://web.archive.org/web/20200305121928/https://support.garmin.com/en-US/?faq=QPc5x3ZFUv1QyoxITW2vZ6|archive-date=March 5, 2020|url-status=dead}}</ref>