• SEVENPAR - Helmert / Molodensky Parameter Sets
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Calculation of Parameter Sets for the Spatial Helmert or Molodensky Transformation with seven or three Parameters

SEVENPAR is a tool for the calculation of highly exact transformation parameters for the Spatial Helmert and Molodensky Transformation, which make possible precise coordinate transformations from one reference system into another. The determined transformation parameters can be entered directly into suitable transformation software, e.g. TRANSDAT Coordinate Transformations, or into the calculation software of GPS receivers to do exact coordinate transformations.

The seven or three transformation parameters are computed with a set of individual identical points. Those are points with known coordinates in both reference systems (geodetic datum). Cartesian coordinates, geographical coordinates or UTM coordinates with or wihtout ellipsoidal height using the ellipsoid dimensions are suitable. Identical measuring points of higher order can be usually inquired or referred by the official institutions for measurement. The necessary ellipsoid half-axes and flattenings are available in the program for the selection from lists.

The coordinates of the identical points are tested intensively on outliers and deviations by different statistic procedures. The quality of the computed parameters is documented by a residual matrix and by the computation of the middle, maximum and root mean square (RMS) deviations.

The seven parameters of the Spatial Helmert Transformation are calculated in the three standards "Coordinate Frame Rotation", "Position Vector Transformation" and "European Standard ISO 19111". The three parameters for Molodenky parameter sets are calculated using the "Standard Molodensky Transformation".

Calculation accuracy

All formulas used for the spatial Helmert transformation, the Molodensky transformation and for the statistic examinations are based on strict formulas. Approximations are not used.

There are to determine seven parameters of the spatial Helmert transformation, i.e. three translations, three rotations and a scale correction. The parameters are calculated by the compensation according to the method of the smallest squares (L2 norm, Helmert transformation). Therefore must be dissolved a formula system with seven equations and seven unknown quantities. The resulting parameters are calculated in the three most usual standards. Those are the Coordinate Frame Rotation, the Position Vector Transformation and the European Standard ISO 19111. Small-scale Helmert parameter sets, for example for an urban area, are very accurate and can be effective up to the centimeter range. Large-scale parameter sets, for example for an entire country, may well lie in the submeter range.

For the Molodensky transformation the program determines three parameters, i.e. three translations. The Molodensky transformation is one of the most widely used methods for transforming geodetic coordinates from one datum to another. The three parameters for Molodenky parameter sets are calculated using the Standard Molodensky Transformation. It is also one of the least accurate, due in large part to the fact that it does not account for rotation or scaling between datums. Errors on the order of meters are the norm with Molodensky transformations.

The coordinates of the identical points are tested intensively on outliers and deviations by different statistic procedures. The quality of the computed parameters is documented by a residual matrix and by the computation of the middle, maximum and root mean square (RMS) deviations.

The program SEVENPAR was tested with a reference program of the Geodetic Land Survey of the German state Mecklenburg-Vorpommern. The determined seven parameters of the spatial Helmert transformation exhibited only extremely slight deviations. With the translations dX, dY, dZ the deviation is less than 0,00001 meters; that corresponds the hundredth of a millimeter. With the rotations dRX, dRY, dRZ the deviation is less than 0,000001 seconds; that corresponds the millionth of a second. With the scale correction parameter dM the deviation is less than 0,000001 ppm.

Multilanguage support

The program SEVENPAR is equipped with a modern graphical user interface of which handling is to understand intuitively. For each window detailed help texts can be shown. The detailed electronic documentation of the program SEVENPAR is available in both English and German language. However, the user interface can be represented in many languages. For this purpose, external language files are used. When starting the program, it notes which language files are available in the calling directory. The found languages then are provided for selection in a list box. By  creating new language files, new languages can be added to the program SEVENPAR at any time.

Network ability

The program SEVENPAR can be run on most common networks. The client installations works automatically. It is possible to use Terminal Services on WINDOWS Servers like e.g. "Citrix Terminal Server".

Pricing, ordering and licensing

Pricing and ordering information can be found in the  Price list. For available licensing options have a look to the  License page. Order the program with the electronic  Order Form.

Download of the test version

The free test version of the program with a detailed user manual can be  downloaded as ZIP packed file by the Internet. For unpacking the download file you need an unzip program, which you can download  from this side.