GPS Solut DOI 10.1007/s10291-012-0255-y ORIGINAL ARTICLE

Abstract

the National Oceanic and Atmospheric Administration, recently released version 3.1 of the Horizontal Time-Dependent Positioning (HTDP) utility for transforming coordinates across time and between spatial reference frames. HTDP 3.1 introduces improved crustal velocity models for both the contiguous United States and Alaska. The new HTDP version also introduces a model for estimating displacements associated with the magnitude 7.2 El Mayor–Cucapah earthquake of April 4, 2010. In addition, HTDP 3.1 enables its users to transform coordinates between the newly adopted International Terrestrial Reference Frame of 2008 (ITRF2008) and IGS08 reference frames and other popular reference frames, including current realizations of NAD 83 and WGS84. A more convenient format to enter a list of coordinates to be transformed has been added. Users can now also enter dates in the decimal year format as well as the month-day-year format. The new HTDP utility, explanatory material and instructions are available a