Pub. 13 2018 Issue 1

27 Issue 1 2018 / UCLS Foresights www.ucls.org D ear Chair Perry and the Executive Board of UCLS, The American Association for Geodetic Surveying (AAGS) would like to make you aware that the National Geodetic Survey (NGS) is actively improving the accu- racyof its hybridgeoidmodel andwill replace GEOID12B with GEOID18 in early 2019. This newhybridgeoidmodel will improve theder- ivation of orthometric heights (elevations) referenced to the North American Vertical Datumof 1988 (NAVD 88) using Global Nav- igation Satellite System (GNSS) technology. The newmodel will also thereafter serve as the official means for obtaining NAVD 88 heights via GNSS. NGS will use GNSS data collected on bench marks to create the new hybrid geoid model. Recent analyses have revealed areas in your state where ad- ditional GNSS data will either confirm or update the relationships between el- lipsoid, orthometric, and geoid heights. In addition to improving the geoid model, the collection and submission of GNSS data on bench marks will also enable NGS to develop more accu- rate models for transforming survey data referenced to NAVD 88 to data referenced to the future North Amer- ican-Pacific Geopotential Datum of 2022 (NAPGD2022). Surveys starting in 2022 involving flood plain maps and so forth will require establishment of vertical control using GNSS; therefore, improving the accuracy of the geoid model is an important endeavor. NGS has developed a prioritized list of bench marks. Data collected and submit- ted on these marks prior to August 31, 2018, will be used in the development of GEOID18. NGS will also continue to accept data on marks through 2020 for the development of the transformation models for 2022. New prioritized lists to support the transformation mod- els will also be made available over the next few years as analysis of data re- quirements progresses. AAGS has obtained a prioritized list of bench marks for your state from NGS (at- tached). This priority list is also shown in a useful, online tracking map at https://geod- esy.noaa.gov/GPSonBM/webmap/. This is an opportunity for your society to help all constituents in your state in need of orthometric heights. Your state society could organize an effort using your chapters to occupy as many of these bench marks as possible. The provided list contains all of the bench marks that NGS would like to have occupied with GNSS and then shared with them. Surveyors can increase the local accuracy of the geoid model in their area by collecting GNSS data on the identified marks, and this effort will thereby help im- prove the accuracy of future GNSS surveys for deriving orthometric heights referenced to the national datum in their area. It is also in your best interest to contribute data as it CONNECTING THE GEOSPATIAL COMMUNITY BY DANIEL GILLINS, PH.D., P.L.S.,AAGS DIRECTOR GEODETIC SURVEYING— GEODETIC continued on page 28