I only have access to v8i but I have contacts that have connect edition and also bentley map so if there are files to be copied we can do that.
What I want is instructions on how to create the GDA2020 ( mga2020) zone 55 datum by export from map to be able to add it to Microstation V8i ss4 manually and be able to have msnt v8iss4 recognise the datum and use it to trans form GDA94 dgns to GDA2020.
BTW Were in Australia
We cannot use CE in our office, I dont have CE nor do I have map
in a past life I had map and was told if I didn't have a datum in v8i, I could create a custom one in map and export it for use in V8i... so why cant we do that for gda2020(mga2020(z54)?
It is possible to create custom datums and custom geographic coordinate systems in v8i SS3 and over, however to create these you need Bentley Map functionality. Once the user-defined coordinate systems are created then these can be used in any v8i SS3 and more Power Product.
In the case of the GDA2020 datum, it is quite easy to create. This datum is to be considered coincident to WGS84 over Australia (non transformation). The problem, however, is not defining this datum but rather a new version of GDA94 that will apply the correct transformation. The older GDA94 used to be considered coincident with WGS84 but after the various linear and non-linear movements of the Australian sub-continent it is not to be considered the case.
The most accurate transformation from GDA94 to GDA2020 relies on the application of a grid shift file in the NTv2 format. It is not possible to define a user-defined datum using this type of transformation. User-defined datum can only use simple transformations (Geocentric [3-parameter] or Coordinate Frame/Position Vector [7-parameter]). There exist such a 7-parameter transformation from GDA94 to GDA2020 and this particular transformation can be user-defined in v8i (with Bentley Map). Here are the parameters if this is the avenue you want to persue.
USE: 7PARAMETER DELTA_X: 0.06155 DELTA_Y: -0.01087 DELTA_Z: -0.04019 ROT_X: -0.00394924 ROT_Y: -0.0327221 ROT_Z: -0.0328979 BWSCALE: -0.009994
To use the more accurate NTv2 based transformation CONNECT edition is necessary.
Hi
Is it not possible to use an V8i NTV2 coordinate system and substitute the based *.GSB file. Seem to be a workaround. for Example:
...MicroStation V8i (SELECTseries4)\MicroStation\GeoCoordinateData\NewZealand\nzgd2kgrid0005.gsb overwrite it with the GDA2020.GSB and use the "newZealand" coordinate system. Just a Try.
Regards
Frank
since 1985: GIS, CAD, Engineering (Civil) Senior Consultant : [Autodesk Civil 3D , Esri ArcGIS, VertiGIS: in previous days : Bentley MS V4 - V8i, GeoGraphics, Bentley Map V8i, InRoads, HHK Geograf, IBr DAVID] : Dev: [C, C++, .NET, Java, SQL, FORTRAN, UML][direct quote by: http://en.wikipedia.org/wiki/Helmut_Schmidt]: "Wer Kritik übel nimmt, hat etwas zu verbergen"Wer Grammatik- und/oder Rechtschreibfehler findet, der darf sie behalten :-)