# # National Water Information System # 2024/10/03 # # # Date Retrieved: USGS Water Data for the Nation Help System # gw_ref_cd gw_ref_ds 1s 58s H Accurate to + or - .01 sec (Differentially-Corrected GPS). 1 Accurate to + or - .1 sec (Differentially-Corrected GPS). 5 Accurate to + or - .5 sec (PLGR/PPS GPS). M Accurate to + or - 1 min. S Accurate to + or - 1 sec. T Accurate to + or - 10 sec. R Accurate to + or - 3 sec (SPS GPS). F Accurate to + or - 5 sec. B Level 1 survey-grade GPS C Level 2 survey-grade GPS D Level 3 survey-grade GPS E Level 4 survey-grade GPS U Unknown or unspecified.