January 17, 2024
Following the updates to Geographic Calculator 2023 SP1, the new GeoCalc v9.2 SDK includes new features and updated geodetic definitions to keep your applications on the cutting edge. The extensive datasource in version 9.2 has been updated to match EPSG v11.001, which includes new data for Denmark, France (Corsica), and Norway and a minor revision for Canada. Other updates include improved projection math to handle edge cases in world projections better and improved GeoCalc Online Update Process efficiency.
Here are additional recent GeoCalc updates of significance:
Parametric Similarity Transformation
GeoCalc now supports the “Similarity Transformation” operation defined by the IOGP’s EPSG working group. This operation is a four-parameter mathematical transformation through rotation (around the Z axis), scale (a single universal scale factor), and translation (in X and Y) in that order. For many years, Geographic Calculator has provided a similarity transformation in two jobs under the name “Helmert Four Parameter.” But whether it be the Point Database Scale and Translate job or the Vector Data Conversion job (manual transformation option), the parameters are entered manually and can only be saved within the job. The new method allows users to create and save a custom Similarity Transformation object in the Datasource for use across jobs. They can even be exported and shared with other users.
Natural Resources Canada BYN grid format
A new natively supported geoid transformation is the BYN format. Natural Resources Canada (NRCAN) uses geoid grids in this format for the CGVD vertical datum of various epochs and combinations of target systems. One of the unique things about geoid transformations, in general, is that no one standard grid format has taken over in terms of common use and popularity around the world. In the realm of horizontal transformations, there have been a few common standards used worldwide, notably the NTv2 grid file standard created by the Canadian government for transformations between NAD27 and NAD83. NTv2 grids have since become very common, with many other governments around the planet adopting the use of this format.
Presently, vertical transformations do not have a clear standard. Almost every geoid in the database has a unique grid type in which its data is stored. The formats for storing geoid grid data are chosen individually by the survey authority for the country where the data applies, and extremely few share a common data format. To implement geoid grids in GeoCalc, it was often simpler to restructure the data into an internal format that was already supported.
Then along came BYN, with several additional grid tables being published, handling many iterations of transformations for the Canadian Vertical Geoid of 2013 and the CGVD 2013a variants. Now, enough new grids are using the BYN format that it simply made sense to add support for the file format itself, such that when new grids are published in the future, GeoCalc SDK users will be able to add them without needing to update their GeoCalc SDK libraries.
New Zealand Deformation Models
Another new method in GeoCalc 9.2 is a deformation model for New Zealand. Deformation models are particularly interesting because they acknowledge that the world is moving. As Dave Doyle, a retired Chief Geodetic Surveyor for the United States, says, “Everything is in motion, all the time!”. Modern coordinate systems are beginning to acknowledge the motion of the Earth’s crust with the development of velocity models that map how the tectonic plates slowly drift around the surface of the planet. However, this slow, steady motion is not necessarily uniform. The plates and surface sometimes warp, twist, crunch together, pull apart, and generally change shape. Localized motion is a complicated factor in dynamic coordinate systems, and that’s where deformation models come in.
These models are time-based by nature and are used to calculate where things were based on the distortions of the entire control networks. Deformation models help us to figure out where things are when a sudden shift in locations occurs, such as before and after an earthquake, but they also apply to slower motions that change the shape of a plate over time. The New Zealand deformation models are one such example. It factors in changes to the New Zealand landmass in snapshots of time, helping to calculate positions at the various points in time around seismic events. This allows specific models to be chosen to reflect a period of time where data may be applied from a particular epoch, similar to how a conventional time-based transformation helps more precisely model the changing earth.
To learn more about the GeoCalc SDK and request a demo, visit bluemarblegeo.com/geocalc-sdk.
