Title: Global Positioning System Survey - Long Session | Geoid Slope Validation Surveys (GSVS) URL Source: https://geodesy.noaa.gov/GEOID/GSVS/global-positioning.shtml Markdown Content: [](https://www.noaa.gov/ "NOAA Home Page")[](http://www.ngs.noaa.gov/ "National Geodetic Survey Home Page") * [NGS Home](https://geodesy.noaa.gov/) * [About NGS](https://geodesy.noaa.gov/GEOID/GSVS/global-positioning.shtml#) * [What We Do](https://geodesy.noaa.gov/INFO/WhatWeDo.shtml) * [Mission and Strategic Plan](https://geodesy.noaa.gov/web/about_ngs/info/mission-strategic-planning.shtml) * [NGS Leadership](https://geodesy.noaa.gov/INFO/leadership.shtml) * [Programs and Products](https://geodesy.noaa.gov/INFO/programs-products.shtml) * [Geodetic Advisors](https://geodesy.noaa.gov/ADVISORS/index.shtml) * [NGS History](https://geodesy.noaa.gov/INFO/history/) * [Policies](https://geodesy.noaa.gov/INFO/Policy/) * [Activities in My Area](https://geodesy.noaa.gov/INFO/activities.shtml) * [Grant Opportunities](https://geodesy.noaa.gov/grant-opportunities/index.shtml) * [Contracting Opportunities](https://geodesy.noaa.gov/ContractingOpportunities/) * [Student Opportunities](https://geodesy.noaa.gov/student-opportunities/index.shtml) * [FAQ](https://geodesy.noaa.gov/faq.shtml) * [Contact Us](https://geodesy.noaa.gov/INFO/NGSinfo.shtml) * [Data & Imagery](https://geodesy.noaa.gov/GEOID/GSVS/global-positioning.shtml#) * [OPUS Share](https://geodesy.noaa.gov/OPUS/view.jsp) * [Survey Mark Datasheets](https://geodesy.noaa.gov/datasheets/) * [NGS Web Map](https://geodesy.noaa.gov/datasheets/ngs_map/) * [NOAA CORS Network (NCN)](https://geodesy.noaa.gov/CORS/) * [Antenna Calibration Data](https://geodesy.noaa.gov/ANTCAL/) * [Remote Sensing](https://geodesy.noaa.gov/RSD/rsd_home.shtml) * [Storm Imagery](https://storms.ngs.noaa.gov/) * [Coastal Imagery](https://geodesy.noaa.gov/web/APOS2/APOS.shtml) * [Shoreline Data Explorer](https://geodesy.noaa.gov/RSD/cmp_data.shtml) * [Orthomosaics](https://coast.noaa.gov/dataviewer/#/imagery/search/where:projectid=1020) * [Lidar](https://coast.noaa.gov/dataviewer/#/lidar/search/where:projectid=24) * [Aeronautical Data](https://geodesy.noaa.gov/AERO/aero.shtml) * [Gravity Data](https://geodesy.noaa.gov/GRAV-D/data_products.shtml) * [Tools](https://geodesy.noaa.gov/GEOID/GSVS/global-positioning.shtml#) * [Process GPS Data (OPUS)](https://geodesy.noaa.gov/OPUS/) * [Coordinate Conversion and Transformation Tool (NCAT)](https://geodesy.noaa.gov/NCAT/) * [Geodetic Tool Kit](https://geodesy.noaa.gov/TOOLS/) * [Geodetic Software](https://geodesy.noaa.gov/PC_PROD/) * [Web Services](https://geodesy.noaa.gov/web_services/) * [Vertical Datum Conversions (VDATUM)](http://vdatum.noaa.gov/) * [GPS Toolbox](https://geodesy.noaa.gov/gps-toolbox/) * [GEOID18 Computation](https://geodesy.noaa.gov/GEOID/GEOID18/computation.html) * [Adjust Leveling (LOCUS)](https://geodesy.noaa.gov/locus/) * [Horizontal Time-Dependent Positioning (HTDP)](https://geodesy.noaa.gov/TOOLS/Htdp/Htdp.shtml) * [Surveys](https://geodesy.noaa.gov/GEOID/GSVS/global-positioning.shtml#) * [Survey Project Proposal Form](https://geodesy.noaa.gov/SurveyProposal/) * [OPUS Share](https://geodesy.noaa.gov/OPUS/about.jsp#sharing) * [Mark Recovery](https://geodesy.noaa.gov/surveys/mark-recovery/index.shtml) * [User-submitted Survey Projects (Bluebooking)](https://geodesy.noaa.gov/FGCS/BlueBook/) * [Geoid Slope Validation Survey (GSVS)](https://geodesy.noaa.gov/GEOID/GSVS/) * [Calibration Base Lines (CBLs)](https://geodesy.noaa.gov/CBLINES/calibration.shtml) * [GPS on Bench Marks](https://geodesy.noaa.gov/GPSonBM/) * [GRAV-D](https://geodesy.noaa.gov/GRAV-D/) * [Height Modernization](https://geodesy.noaa.gov/heightmod/) * [Leveling](https://geodesy.noaa.gov/leveling/) * [Science & Education](https://geodesy.noaa.gov/GEOID/GSVS/global-positioning.shtml#) * [Datums and Reference Frames](https://geodesy.noaa.gov/datums/index.shtml) * [New Datums](https://geodesy.noaa.gov/datums/newdatums/index.shtml) * [Research](https://geodesy.noaa.gov/research/index.shtml) * [Geoid Models](https://geodesy.noaa.gov/GEOID/) * [Conferences/Training](https://geodesy.noaa.gov/web/science_edu/training/) * [Upcoming and Recent NGS Presentations](https://geodesy.noaa.gov/INFO/conferences.shtml) * [Educational Videos](https://geodesy.noaa.gov/corbin/class_description/NGS_Video_Library.shtml) * [Online Lessons](https://geodesy.noaa.gov/web/science_edu/online_lessons/index.shtml) * [Webinar Series](https://geodesy.noaa.gov/web/science_edu/webinar_series/) * [Presentation Library](https://geodesy.noaa.gov/web/science_edu/presentations_library/) * [Publication Library](https://geodesy.noaa.gov/library/) * [Commemorative Marks](https://geodesy.noaa.gov/commemorative/index.shtml) * [Applications of Geodesy](https://geodesy.noaa.gov/INFO/applications-of-geodesy.shtml) # Global Positioning System Survey - Long Session The Global Positioning System (GPS)is one example of many Global Satellite Navigation Systems (GNSS) that provide extremely precise (~1cm) positioning relative to the Earth Ellipsoid. The Earth Ellipsoid is a mathematically well defined surface that, on average, best fits the form of the Earth (approximated by an ellipsoid of rotation). In the GSVS, long session (24 hours or more) GPS results are used to precisely locate the bench marks relative to the Earth Ellipsoid, providing latitude, longitude, and ellipsoidal height (height above or below the Earth Ellipsoid). This information is used to both locate the various survey instruments (for numerous location dependent corrections) and serves to determine the distance between bench marks when calculating geoid slopes (the "run" in "rise over run"). ## Geoid Quick Links * [Geoid Home](https://geodesy.noaa.gov/GEOID/) * [Geoid Models](https://geodesy.noaa.gov/GEOID/models.shtml) * [Publications](https://geodesy.noaa.gov/GEOID/geolib.shtml) * [Geoid Research](https://geodesy.noaa.gov/GEOID/research.shtml) * [Geophysics of the Geoid](https://geodesy.noaa.gov/GEOID/geophysics.shtml) * [Geoid Slope Validation Surveys (GSVS)](https://geodesy.noaa.gov/GEOID/GSVS/) * [Research Geoids](https://geodesy.noaa.gov/research/geopotential-datums/research-geoids.shtml) ## Questions? * [Contact the Geoid Team](https://geodesy.noaa.gov/GEOID/contact.shtml) Website Owner: National Geodetic Survey/Last modified by [Gravity Webmaster](https://geodesy.noaa.gov/cgi-bin/redirectM.prl?u=bill.waickman&d=noaa.gov&s=Web%20Comments%20/GEOID/GSVS/global-positioning.shtml&b=Re:%20/GEOID/GSVS/global-positioning.shtml) Jun 03 2020 [NOS Home](https://oceanservice.noaa.gov/)![Image 1: bullet](https://geodesy.noaa.gov/ngsstandard/images/redbullet.gif)[Privacy](https://geodesy.noaa.gov/privacy.shtml)![Image 2: bullet](https://geodesy.noaa.gov/ngsstandard/images/redbullet.gif)[Feedback](https://geodesy.noaa.gov/survey.shtml)![Image 3: bullet](https://geodesy.noaa.gov/ngsstandard/images/redbullet.gif)[Disclaimer](https://geodesy.noaa.gov/disclaimer.html)![Image 4: bullet](https://geodesy.noaa.gov/ngsstandard/images/redbullet.gif)[USA.gov](https://www.usa.gov/)![Image 5: bullet](https://geodesy.noaa.gov/ngsstandard/images/redbullet.gif)[Ready.gov](https://www.ready.gov/)![Image 6: bullet](https://geodesy.noaa.gov/ngsstandard/images/redbullet.gif)[Information Quality](https://www.noaa.gov/organization/information-technology/policy-oversight/information-quality)![Image 7: bullet](https://geodesy.noaa.gov/ngsstandard/images/redbullet.gif)[Site Map](https://geodesy.noaa.gov/sitemap.xml)![Image 8: bullet](https://geodesy.noaa.gov/ngsstandard/images/redbullet.gif)[Contact Us](https://geodesy.noaa.gov/cgi-bin/redirectNOAA.prl?u=ngs.infocenter) [![Image 9: Return to Top](https://geodesy.noaa.gov/ngsstandard/images/back_to_top_btn.png)](https://geodesy.noaa.gov/GEOID/GSVS/global-positioning.shtml#)