Gemini  

What is Gemini Least-Squares Adjustment Software?

Gemini Least-Squares Adjustment Software is a suite of libraries and programs for adjusting surveying and geodetic data and estimating coordinates, heights, and gravity among networks of points. It is an extension of software developed by Polaris Geospatial Services (PGS) for the US National Geodetic Survey (NGS). Gemini can adjust networks of any size, and it supports free network adjustments. It also allows for the adjustment of calibration-baseline data as well as the estimation of vertical gravity-gradients.

Gemini has a modern graphical user interface that runs on both Windows and Linux computers. It was written in modern C++ language by a team of PGS geodesists and computer scientists that have expertise in least-squares adjustment theory and a combined decades of experience in scientific and commercial software development.

A free 30-day trial of Gemini is available to anyone interested in trying it out (download below). Degree seeking students can use Gemini free of charge on an annual basis. Please contact PGS for more information or for Gemini licensing prices.

Gemini features 

• Supports 3D geodetic networks, local networks, leveling networks, gravity networks, calibration baselines, vertical gravity gradients.

• Features a modern graphical user interface (GUI) for its geodetic, leveling, and local network adjustments on Windows and Linux. All adjustment types can also be run from a command line interface on Windows and Linux.

• Includes comprehensive reports and sortable tables of all outputs. Displays network maps in Google Earth and draws error ellipses for estimated coordinates and histograms for residuals.

• Suitable for networks of all sizes, from small surveying networks to large national networks.  

• Supports minimally and overly constrained adjustments, including free network adjustments.  

• Allows constrained and unconstrained a priori coordinates to be specified in Earth Centered Earth Fixed (ECEF) Cartesian, geodetic, or map projection (state plane 1983 or UTM) coordinate systems.

• Performs 3D network adjustments in 3D geodetic space for the utmost in modeling accuracy, outputting estimated coordinates in ECEF Cartesian, geodetic, and map projection (state plane or UTM) coordinate systems. 

• Allows network adjustments in local, arbitrary coordinate systems with a mix of 1D, 2D, and 3D points.

• Supports computation of Relative Positional Precision (as defined by ALTA/NSPS) between any two points within the network.

• Provides easy to create and read data formats; also supports NGS bluebook and GDX/GVX data formats. 

• Provides many computational options through program settings, including: 

• Blunder checks 

• Loop closure checks 

• Outlier detection 

• Hypothesis testing on constraints 

• Multiple variance component estimation  

• Supports units of meters and feet. 

• Supports specification of centering errors at instrument and target stations. 

• In addition to extensive reporting within the program, Gemini also outputs a plethora of files showing adjustment results, including: 

• Text files 

• CSV files that can be viewed in spreadsheets 

• KML files for viewing network maps in Google Earth and GIS programs 

• GMT script files for creating network maps, error ellipses, and residual histograms using GMT (Generic Mapping Tools)   

• Python and MATLAB scripts for observation and normal equations – useful for students and researchers 

• Includes an extensive user’s manual that describes the software and explains the theory of least-squares adjustments and associated statistics.

• Includes several YouTube videos that demonstrate how to use the program at https://www.youtube.com/@PolarisGeospatialServices.