23 August 2007

Dispensing with the PC

Thanks to Tony, and Thorsten Lemke from Lemkesoft GmbH (developer of Graphic Converter), you can now dispense with a Windows PC to transfer the New South Wales Department of Lands' Topoview DVD Raster 2006 NSW topographical maps to your Macintosh for use in MacGPS Pro. You will need a Macintosh computer with a DVD reader to read the DVD.

I couldn't open the maps from the DVD with anything on the Mac, no matter what I tried. Graphics Converter was supposed to open .ecw files, but I kept getting an error message. I even installed the ExpressView Browser Plug-in (MrSID) for Macintosh thinking the maps may be encoded.

The trick? Copy the .ecw files off the Topoview DVD onto your hard drive before trying to open them with Graphic Converter!

So the process (without PC) is as follows:
  1. Purchase the Topoview DVD Raster 2006.
  2. Download Graphic Converter.
  3. Pay Lemkesoft.
  4. Find the map you want: use the Topographic Key Maps for New South Wales to get the sheet number and sheet name for the map you want. The Topoview maps are stored on the DVD either by the sheet number of the map or sometimes a version of the name. For example, the file on Topoview containing the Perisher Valley 8525-2S map is 8525s.ecw, but the name for the Youngal 8525-3S map next to it is youg3s.ecw: there is a text file called mapdata.txt that contains all the information to allow you to find the correct file, I'm working on a lookup table solution but you can just open the file and find the filename for the map you want fairly easily.
  5. Copy the map file from the Topoview DVD to a writeable drive.
  6. Open the file you copied with Graphic Converter (File>>Open...). The Define ECW import area and scale window will appear. In this window you can scale the map or select a portion of the map to convert. To convert the entire map just click OK.
  7. Assign no Profile in the Assign Color Profile dialogue box.
  8. Save the file as a PICT file with the default options.
  9. In MacGPS Pro, select Import Raster Map or Chart... from the File menu. Choose the file you just saved from Graphic Converter, and click the Open button.
  10. You will be prompted to save the converted map. Choose a suitable directory and click the Save button.
  11. Since the file has no geo data associated with it, the following dialogue will appear.

  12. Click OK. Set the Geodetic Datum to GDA94, and the Map Projection to Transverse Mercator in the Set the map's Datum and Projection type dialogue.

  13. The map is a UTM Map. See http://www.werple.net.au/~gnb/gps/mapping.html for an overview of the UTM zones in Australia, and enter the appropriate Zone in the UTM Zone: text box. This is the only data you need to enter in this dialogue: the rest of the entries are auto-filled. If you don't get the Zone exactly right, MacGPS Pro will give you an error when you try and calibrate the map in later steps, telling you the coordinates entered are outside the allowed range for the projection etc. Close the file and start again from Step 9.

  14. Click the OK button. You now have to enter the latitude and longitude of a couple of known points on the map to calibrate it. I use the top left and bottom right of the maps because the latitudes and longitudes are printed on the maps for those points (among others). So click the top left of the map (make sure you have the Show Map Location tool selected: the cross-hairs on the extreme left of the tool bar).

  15. Click OK in the Click on Known (GDA94) Points to calibrate Map dialogue, navigate to the bottom right of the map window and click there with the Show Map Location tool. Enter the latitude and longitude for that point, click OK, and then click Done (also in the Click on Known (GDA94) Points to calibrate Map dialogue). Your changes will be saved automatically with the map file, so next time you open it the map will be calibrated already.
That's it!

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