## Least-squares network adjustment software package

JAG3D (Java·Applied·Geodesy·3D) is one of the most popular open source least-squares software package for geodetic sciences.
The application is distributed under the terms of the GNU General Public License (version 3). JAG3D is designed to combine hybrid
terrestrial observations like leveling, directions, distances or vertical angles in a uniform and rigorous mathematical model.
Moreover, GNSS baselines that are derived by Global Navigation Satellite System (GNSS) techniques are supported. Terrestrial
observations as well as GNSS baselines are combined together during a single adjustment process. The software supports pure
leveling networks, horizontal networks and spatial networks but also combined multidimensional networks. Spatial observations
will not be splitted into two parts, i.e. a height component and horizontal component. Thus, mathematical dependencies between
the coordinate components will be rigorously considered. Additional parameters like orientations, scales, zero point offsets or
integration parameters of GNSS baselines can be estimated beside the coordinates of the points. Three network designs are
supported: free network, dynamic network, and hierarchic network. The least-squares adjustment is formulated as Gauß-Markov model.
High performance algorithms and sparse techniques are used to solve the system of equations which are provided by the de facto
standard algebra packages BLAS/LAPACK.

For data analysis, JAG3D estimates several parameters to evaluate the observations and the network characteristics.
Based on the universal statistic tool box of Baarda's data snooping, F-distributed test statistics are derived for significance tests
e.g. outlier detection or point shifting. The geometrical stiffness of a network can be evaluated by principal component analysis.
Combining the original observations of two epochs, JAG3D can carry out a congruence analysis on the observation level. Special
deformation patterns are provided that allows for identification of block-shifts or strains of a part of the network. The a-priori
uncertainties of the stochastic model are validated by variance components estimation. Moreover, in the framework of network optimization,
i.e. an optimal datum (zero order design), a suitable network configuration (first order design) or an optimization of the observation
uncertainties (second order design), JAG3D supports a pre-analysis of an intended network.

JAG3D estimates deflections of the vertical, if the local spatial coordinate reference frame of the instrument is tilted w.r.t.
the global spatial reference frame. The estimation of deflection of the vertical allows for processing of measurements where the
compensation unit of the instrument must be disabled, e.g. in moving environments like floating docks. In industrial metrology,
most of the global reference frames are defined as object-based coordinate system and height-precision instruments like Laser Trackers
are not linked to the gravity field. Here, the deflections of the vertical allows for rigorous combining of the measurements on
the original observation level.

## OS-independent adjustment software

JAG3D provides a clear and easy to use graphical user interface. JAG3D’s user interface handles the complete analysis process,
i.e. data-management, administration of the least-squares adjustment as well as analyzing of the adjustment results. The full project
data and properties are stored in the relational database management system, the Hyper SQL Database (HSQLDB). JAG3D is written in the
platform-independent programming language Java and, therefore, the software is runnable at each platform and operation system that
provides Oracle's java runtime environment. JAG3D is portable - no need to install or uninstall. Just download, unpack and run.