Upload data file
Upload your vertical observation (*.hgz ) file to LOCUS to receive a least-squares adjustment of orthometric heights with all available corrections applied. The file must have no errors after being checked by Translev (v4.16.07 or later). Translev is available from the Download NGS PC Software web page.
If the file contains PIDs of published bench marks, there is the option to select one or more PIDs to constrain from a dropdown list. Constraining a single PID produces a free adjustment if the leveling data in the *.hgz file form one or more loops. Marks occupied more than once introduce redundancy, and the resulting misclosures are distributed through the loop(s) as corrected and weighted observations to obtain the most likely unique heights on all bench marks.
Constraining multiple PIDs produces a partially or fully constrained adjustment. Tools for analyzing the statistical results of a constrained adjustment are not currently available in LOCUS, but such functionality will be developed for a future version.
For a single (spur) level line with no loops, the heights are not actually adjusted (all residuals are zero), even when the line includes forward leveling and backward leveling. This occurs because in the reduction process for leveling data, the set of field observations between two bench marks are combined into a single “observation” for performing the least-squares adjustment. Thus a leveled spur line consists of only single (averaged) observations between adjacent bench marks. Because of this, such a spur has no redundancy, and in a free adjustment (constrained to a single mark), the heights will not be adjusted. However, the corrections applied to the leveled height differences can still be substantial, and the leveled height differences observed in the field typically do not equal the corrected height differences.
The default vertical datum used by LOCUS is the North American Vertical Datum of 1988 (NAVD 88), but others may be selected. The vertical datums available in LOCUS are listed below, as abbreviated in the LOCUS datum selection pull-down menu.
| 88 | NAVD 88 (North American Vertical Datum of 1988) | ||
| 29 | NGVD 29 (National Geodetic Vertical Datum of 1929) | ||
| G1 | GUVD 63 (Guam Vertical Datum of 1963) | ||
| GU | GUVD 04 (Guam Vertical Datum of 2004) | ||
| LT | LMSL (Local Tidal Datum) | ||
| NM | NMVD 03 (Northern Marianas Vertical Datum of 2003) | ||
| PR | PRVD 02 (Puerto Rico Vertical Datum of 2002) | ||
| VI | VIVD 09 (Virgin Islands Vertical Datum of 2009 |
