Can't select Unknown projection in MAPCSLIBRARY

[georg.grebenyuk]

Hello all,

May be problems only with me - when I try select in options  projection type = Unknown. I tried created as empty system (non edit current) - but had been got same situation. 

Programm send me first warning:

If I select it again - FATAL ERROR: Unhandled eO434352h Exception at A2DAA859h

I tried on Civil 2018 English, Civil 2021 (Rattlesnake Beta Metric), Civil 2019-2020 Russian - there is one fatal error with that code (above). 

It's strange that there are no similar posts in Forum (or may be I can't find it).

P.S. If I selected coordinate system non-Geodetic Civil crashed from first attempt

May be it's type non supported or I must use it with some conditions........

[Pointdump]

Hi Egor,
Trying to break Map 3D again, eh? I have no idea why Autodesk would include that "Unknown" Projection type. As for Datum, Geodetic is Perpendicular to Ellipsoid, Geocentric references center of Earth, and Astronomic references Gravity at a particular point. I have no idea why anyone would choose "None".

Dave

[Koesti]

Hi @georg.grebenyuk ,

thank you for reporting this issue, now we have a documented change request to remove the entry of "unknown", or at least should not result in error.

In general the definition of the transformation from user defined CS to WGS84 can be set in the coordinate system library in geodatic transformation. 

Maybe the following article help:

How to configure transformation for custom coordinate system in Map 3D or Civil 3D.

Kind Regards

[georg.grebenyuk]

Hi, Brigitte

Yeah, I read that article, but situation around "Geodetic Transformation Paths" is still unknown for me . In article there is info: "...For example, you might have two drawings: one that uses geographic coordinate system A..."

1. Then I can't use "Geodetic Transformation Paths" to calculate between PROJECTIONS systems?!
2. As I analysed avaliable "paths" in Library - all (a big part) of them are defined for WGS-84 and a lot of them (or all) require GSB files and I can't understang logic all that processes: you want say that I can't use "Geodetic Transformation Paths" wihout GSB or how? There are no examples of working that "paths" and I as usual User don't understand that info in Help's guide.

Sorry for that expressive request but I'm tired finding info how it work!

[Koesti]

Hi @georg.grebenyuk ,

the main point seems to be to figure out which transformation is used for which coordinate system - correct?

The sample from Germany might help:

We have the "old" CS Gaus Krüher (DHDN) and need to transform all data to the new ETRS.UTM-32n.

Some customers like to transform via GRIS files and others via the seven parameter method.

So we have 2 CS, which are the same but have different Datum and the transformation from Datum to Datum is set in Geodetic Transformation.

Sampel:

DHDN/3.Gauss3d-3 with Datum: DHDN/3 use 7 parameter to transformation to UTM --> geodetic transformation: DHDN/3_to_WGS84

DHDN/BeTa.Gauss3d-3 with Datum: DHDN/BeTA use GRID transformation to UTM --> geodetic transformation: DHDN/BeTa_toETRF89

The .dwg should get the correct CS assigned regarding the transformation methode.

Additional there is a third CS based on the same Gauss-Krüger: DeutscheBahn Gaus Krüger using

7 Paramter transformation with Geodetic Transformation and Geodetic Transformation path.

What I try to explain is that the Geodetic Transformation is done via Datum to Datum and the coordinate system needs to have the correct Datum assigned related to the transformation method.

I hope that makes somehow sense, it is difficult to describe in words.

Kind regards

[georg.grebenyuk]

Thank you for detail example. In your case there is conversion "DHDN/BeTA_to_WGS84" that consists of two transformations: one need GSB files and second "ETRF89_to_WGS-84" with null transformation. So for use Geodetic Transformation path is compalsory to use GSB files or you can give example of other situation in definition of "Geodetic Transformation path" where there are not GSB files?

In Russia there are no GSB files (it have "secret status" or non actual) and I have'n any ideas in Cases how transform data from one system to another. I thought that "Geodetic Transformation path" works as "summ" parameters from geodetic transformation's definition in formula of "Geodetic Transformation path". 

I agree that it difficult Topic and it's hard to write about it. 

[Pointdump]

Egor,
I thought that "Geodetic Transformation path" works as "summ" parameters from geodetic transformation's definition in formula of "Geodetic Transformation path".

My understanding (shallow and pitiable) is that a Geodetic Transformation Path is only necessary to define a "chain" of transformations. First this, then that. But I'd really like to know how to determine when a transformation must follow a "chain".
Dave