Have you been confronted with the infamous Error crs:76 – Multiple datum transform paths are available…?
When using Petrosys in a new region, there may be a number of possible transformations between the CRS of the data sources and the target CRS of your map, or there may be no transformation method defined betweeen them. Petrosys requires that only one transformation be used for a given GeogCRS transformation in a project at one time.
All GeogCRS transformations are approximations. The more accurate transformations are generally slower to process and may be restricted to smaller geographic areas. For practical workflows it is appropriate to chose a transformation method that has a sufficiently broad regional coverage that it can be used for all the data in a project, and which is sufficiently fast that it won’t have an impact on your mapping productivity; whilst at the same time being sufficiently accurate for your business needs.
This multiple transform issue frequently arises where there is a standardization towards a WGS84 related datum such as NAD83, GDA94, NZGD2000, and SIRGAS2000.
As at year 2011 the petroleum geoscience and reservoir engineering business accepts a transformational accuracy in the order of +/- 1metre, which is often satisfied by one fast ‘Molodensky’ transformation over a region the size of the states of Texas USA, Queensland Australia, or countries such as Norway or Malaysia. However different Molodensky transforms might be required for the same GeogCRS transformation in neighbouring states and countries.
In the future, faster information technology and better geomatic engineering will enable more precise and consistent transformation of historic data. Petrosys allows you to maintain and use your historic spatial data as the raw numbers originally acquired, keeping open the opportunity to apply future technology to past data, maintaining the quality of painstakingly acquired spatial relationships that might otherwise be lost through transformation compromises.