About LOCUS
The Leveling Online Computations User Service (LOCUS) is a Web utility developed by the National Geodetic Survey (NGS). The purpose of LOCUS is to simplify the office processing and adjustment of geodetic leveling, including, as a long-term goal, the submission of leveling projects to NGS for publication. LOCUS runs the same programs that NGS uses in-house to process and adjust submitted projects.
LOCUS version 1.0 will be limited to:
Correction of observations for systematic errors, a minimally constrained [free] and fully constrained least-squares adjustment. Network adjustment are not supported.
A correctly formatted NGS Bluebook vertical observation (*.hgz) file must be submitted (the vertical observation format is described in Chapter 6 of the NGS Bluebook). The *.hgz file must first be checked to be error-free by the NGS program Translev (v4.16.07 or later). The NGS program WinDesc must also be used to provide positions of all marks and the Permanent Identifiers (PIDs) of published bench marks into the Translev program.
If more than one published bench mark is included in the *.hgz file, users will see the list of all PIDs available to constrain, and they may choose to do a partially or fully constrained adjustment. However, the tools to analyze the results of a constrained adjustment will not be implemented in the first version of LOCUS. Naturally, the adjusted orthometric heights of new marks will vary according to which constraints are held. Thus, results obtained using LOCUS and adjusted with user-supplied constraints may differ somewhat from results adjusted using constraints determined by NGS for publication.
To the extent possible, corrections for systematic errors are made before the adjustment. Refer to NOAA Technical Memorandum NOS NGS 34, “Corrections Applied By The National Geodetic Survey To Precise Leveling Observations” and to the LOCUS Equipment & Corrections page for more information. Note that in the absence of level rod calibration and/or temperature data, certain corrections are not applied.
At present, the adjusted orthometric heights are not eligible to load from LOCUS into the NGS dababase. No PIDs are generated for new marks. The output files are compressed in a file available for download.
