[SS10] - Various geographic coordinate Systems on same project

Question

I myself am good about checking/setting the correct geographic coordinate system in any new files when I first create them. However, I just got on a project that has been going on for a very long time and I noticed that there are many different or even no geographic coordinate systems being used in all the different dgn files, likely unknowingly to the users (see attached screenshot of some of the ones I've found to be used). Everything seems to be talking well with each other in terms of referencing and things being located where they need to be. I don't have a good understanding of the potential negatives with this scenario or if there even are any, so my question is: Is this ok like this or do I need to alert people and do something to fix? I know if you change a coordinate system in a file that already contains element and/or references it will automatically attempts to re-project them which would be bad and cause headaches. Any thoughts or advice would be welcome. 
 Thanks!

Lorys · Answer

Hi Steven 
 Yes we have experienced this too. 
 It really is an education process to make sure everyone on the team understand use the same datum or GCS and this needs to be stated and emphasised at the beginning of the project and that for the life of the project we all must use the same datum and GCS and same seed files. 
 I have an issue here Australia where we have had the new national datum MGA2020 which is now mandatory.. so I make sure this is enforced first with the Surveyors as they understand it best. Now this datum is not available in V8i SS10 so even though I set the datum in Connect in all the seed files for microstation users , V8i does not see this datum.. but now comes the important part v8i doesnt care as long as every xref is always attached as wold coincident and we all use the same seed files.. the biggest problem with this is ESRI Shape files ie shp GIS file data as it may come as a different or earlier datum ... and V8i will not recognise the current seed file datum and may not reproject the shp file correctly.. First need to open the prj file in notepad to determine what datum is used.. if its the same as seed file great no problem.. if its not and that datum is not available in v8i then you cannot use this shp file in v8i you need to use CE to open and import the data into the dgn in the same datum as your seed file then you can go back to V8i and use it ref attached world coincident.. no reprojecting ... the same problem can happen with airphotos... 
 If you dont have access to CE you will need to get a GIS program user to change your shp files to the same datum as your DGN files and also your airphotos rasters so that in v8i its still all world coincident ... ie relative to 0,0 
 We had the same problem pre v8i when we had to change over from AMG66 to MGA94 for a few years we just had to make sure everything was from surveyors and airphotos were in the current same datum and always use world coincident .. back then we could not set or read datums or GCS in plain microstation.. we had to use another program I think it was microstation GEOGRAPHICS or THEOGRAPHICS ( was free from Bentley Select as a simple GIS package) to do some of what V8i and CE does now ... 
 The only other bad thing is with no readable datum or no GCS set that V8i can read you cannot use Bing, nor use Google earth integration ( my favourite features) for that you need to have a compatible GCS or datum set and readable.. so I jump into CE for that to check stuff like missing road names and check design aligns with real world or missing photo coverage so I use Bing or google earth and also to make KMZ files of our design for Google earth users to view the design on top.. this is getting asked for more and more by clients and other project partners and managers who dont need or even have CAD.. ( KMZ great for presentations and better than pdfs ) 
 I hope this helped please reach out through private messaging if you need some specific help or better explanations.. its a big topic and my post is probably way too long and detailed for most readers here.