Editing Draper Laboratory (section)

===Inertial navigation===
The laboratory staff has studied ways to integrate input from [[Global Positioning System]] (GPS) into [[Inertial navigation system]]-based navigation in order to lower costs and improve reliability. Military inertial navigation systems (INS) cannot totally rely on GPS satellite availability for course correction (which is necessitated by gradual error growth or "drift"), because of the threat of hostile blocking or jamming of signal. A less accurate inertial system usually means a less costly system, but one that requires more frequent recalibration of position from another source, like GPS. Systems which integrate GPS with INS are classified as "loosely coupled" (pre-1995), "tightly coupled" (1996-2002), or "deeply integrated" (2002 onwards), depending on the degree of integration of the hardware.<ref name="Schmidt">{{cite journal| last =Schmidt| first =G.| author2 =Phillips, R.| title =INS/GPS Integration Architectures| journal =NATO RTO Lecture| volume =Advances in Navigation Sensors and Integration Technology| issue =232| pages =5-1–5-15| publisher =NATO| date =October 2003| url =http://ftp.rta.nato.int/public/PubFullText/RTO/EN/RTO-EN-SET-064/EN-SET-064-05.pdf| access-date =2013-12-28| url-status =dead| archive-url =https://web.archive.org/web/20131230234614/http://ftp.rta.nato.int/public/PubFullText/RTO/EN/RTO-EN-SET-064/EN-SET-064-05.pdf| archive-date =2013-12-30}}</ref> {{As of|2006}}, it was envisioned that many military and civilian uses would integrate GPS with INS, including the possibility of artillery shells with a deeply integrated system that can withstand 20,000 [[g-force|g]], when fired from a cannon.<ref name = "NATO"/>