Hello All Firstly, thanks to those who replied. It appears by the replies that I received, that most sites are still planning to migrate, as approximately 90% of the responses were "let me know what you find out" - hence the summary to the list.
I only received one reply from a Victorian developer who is creating his own application with documentation suppled by Land Victoria, all others looking at FME for the solution. (See Steve's comments below) Secondly, by no means is this e-mail intended to "bag" SAFE's excellent product, FME (as it many more features than what I used it for, and I also want to admit I have limited experience with their product (3 months purely for GDA conversion)). I think that the issue of Australians converting MapInfo data between datums is not the major reason for the development of FME (which I appreciate and understand). However, I did want to make other Australian users aware of the issues I've previously discovered and ask if anyone has found solutions for them. Using the option in MapInfo to convert between the Australian Geodetic Datum (AGD) and the new Geocentric Datum for Australia (GDA) (File - Save As, and change the projection) does not use the State's distortion model / grid and therefore introduces varying errors of 1.73m (average) for the eastings and 0.08m (average) for the northings in our data here on the Gold Coast. Because large sums of money have been invested in collecting our data, this option is not acceptable for our user's needs. When using FME in batch mode (over 20,000 MapInfo layers with my previous employer) I discovered the following; (please note this was a build of FME from early 2001 - these may have been fixed by SAFE by now and may no longer be a concern) * Small Symbology Changes in batch mode - transparent objects lost transparency and slight changes in fill styles. * Data not in AGD (eg any other datum / projection) was not converted. The user must specify specific input and output datums in FME. A check was performed to change all the user's data to AGD first - it's surprising to see the amount of existing data not saved in the current datum in a distributed GIS environment. Not a huge issue, nor FME's fault. * Indexes disappeared after the conversion. These needed to be recreated after converting to enable searches to take place again. * Variations on Tab files crashed entire batch files (one batch per directory) - When processing through a directory, if FME finds a tab file that contains a "note", "run application" (that we inserted), seamless tables, raster tables or tabs that point to other tab files, etc, etc, it skips over the files in the rest of that directory. These "non-standard" tabs had to be stripped out then replaced after the transformation. * FME creates *.MAP files for layers that did not have one before the transformation (eg Browsers). Easy solution - delete the 1k .maps after conversion. These are not huge issues, but something I feel users should test for before they convert all their data. Also don't forget to modify your Workspaces (as they mention the map projection - change to "33") and any MBX that creates a new table (same situation). I also received an email that indicated that the AURISA conference that will be held in Melbourne in November 2001 will have a GDA94 transition workshop. I hope this helps and please let me know anything new you have discovered. Shane ~~~~~~~~~~~~~~~~~~ STEVE's COMMENTS ~~~~~~~~~~~~~~~~~~~~ I've been doing some experimenting with Grid transformation files for conversion to GDA and have developed up an application that will do this. The problem is how to handle the grid file; I've gotten round this by converting the grid file itself to a group of MapInfo tables. The node values can then be easily extracted using fetch statements. Land Victoria's site is a good place to look for info. Their GDAit program is very good and I've used their software documentation manual (which has an in depth explanation of how the interpolation process works) as the major source for my code. I also used GDAit to convert the grid file to an ASCII text file that I could then convert to a MapInfo table. Personally I wouldn't be looking at implementing any coordinate transforming process that didn't involve distortion grid transformation as I can't see how you can get sub-metre accuracy out of any other method. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -----Original Message----- From: Olivier Rey lescure [mailto:[EMAIL PROTECTED]] Sent: Wednesday, 19 September 2001 10:27 To: BARRETT Shane Cc: MI-L (E-mail) Subject: Re: MI-L Australian MapInfo Users & GDA Hi Shane, You can display your data in GDA coordinates instead of processing a shift. Simply change the projection to GDA in map/option, that's the beauty of it something that arcview users can only dream of! If still you want your data permanently shifted to GDA, save copy as new table with GDA as projection. Regards Olivier ------------------------------------------------------------------------ --------- Olivier Rey Lescure Cartographer School of Geosciences University of Newcastle Callaghan NSW 2308 tel: (02) 4921 5098 fax: (02) 4921 5877 ********************************************************************** This e-mail and its contents is confidential to Gold Coast City Council and un-authorised use is strictly prohibited. ********************************************************************** _______________________________________________________________________ List hosting provided by Directions Magazine | www.directionsmag.com | To unsubscribe, send e-mail to [EMAIL PROTECTED] and put "unsubscribe MapInfo-L" in the message body.
