25 August 2007

Calibrating NATMAP Raster Premium maps

The topographic maps on Geoscience Australia's Raster Premium DVDs are stored in .ecw zone files: one file for each of the 8 MGA (Map Grid of Australia) Zones that cover Australia.These files are very large, but you can open them in Graphic Converter on the Macintosh and excise the bit of the map you want and save it as a PICT file for MacGPS Pro. To use these maps on the Macintosh you will have to save them in a format the Mac understands, and calibrate the files.

When you import the PICT file into MacGPS Pro, you have to calibrate it manually because no calibration data is saved with the file when you convert it in Graphic Converter. There isn't any calibration data in the .ecw files, anyway, so it's hardly surprising. You will need the MGA Zone (since each of these files includes the Zone in its title, that's not hard to find), and the north-to-south subzone, represented by a letter between C and X (except I and O). This data (the MGA Zone and the subzone, eg 55J) needs to be entered in the UTM Zone text box in MacGPS Pro.

The easiest way to find this data is to use Google Earth. Google Earth is free but you need to be connected to the Internet for it to work.

In the Google Earth Preferences... 3D View pane, select the Universal Transverse Mercator option in the Show lat/long section.

Click OK, and use Google Earth to display on the screen the region where the top left of the map you want to calibrate in MacGPS Pro is. As you move the cursor over the map or image window in Google Earth, the UTM coordinates of the cursor is displayed in the bottom left of the window.

The UTM coordinates you need for MacGPS Pro are the two numbers and the letter following "Pointer": in the image above it's 55J. Note this down. The letter doesn't appear to be case sensitive.

To complete the calibration in MacGPS Pro you will also need the latitude and longitude of at least three points on the map, in degrees, minutes and seconds. Google Earth can help you out with this as well.

Go back to Google Earth Preferences..., and change the Show lat/long setting to Degrees, Minutes, Seconds. Click OK, and find three or more points in Google Earth that you can also see in the map you want to calibrate. As you move the cursor around the window, the Pointer display at the bottom left will show the latitude and longitude in the format you will need to use in MacGPS Pro.

In Google Earth, note the latitude and longitude for at least three points. Choose points spread as widely as possible throughout the map. It's a good idea to note the coordinates of an additional point or two to check the accuracy of the calibration.

Go into MacGPS Pro, import the map file you converted using Graphic Converter, and enter the zone data in the UTM Zone text box. Find the points on the map that you know the latitude and longitude for, click them with the Show Map Location Tool, and enter the data in the Calibrate Map dialogue.

When you've entered enough points (at least two), the DONE button is undimmed and you can click it to complete the calibration process. Don't forget to put a minus sign (-) in front of the latitude to show it's south of the equator.

Once the map is calibrated, choose Find Coordinates... from the Edit menu to search for another location on the map you know the coordinates for to check the accuracy of the calibration.

NATMAP Raster Premium on the Macintosh

Buoyed by the success with getting the Topoview Raster 2006 topographic maps to the Macintosh without a Windows PC, I decided to try Geoscience Australia's NATMAP Raster Premium 1:250 000 topographic maps for the whole of Australia. So I went down to the local MapWorld store in Canberra (it's in Rudd Street, not on Northbourne Avenue as the address would suggest, on the outside of the Jolimont Centre), and picked up a copy. I also picked up for free copies of the Map Index to NATMAP Topographic Maps and the New South Wales Topographic Map Catalog (West and East) to save navigating the Acrobat .pdf files of the indexes.

Unfortunately as far as I can see the maps aren't available individually on the DVD, so the same process that works for Topoview won't work for the NATMAP product to get them into MacGPS Pro. Graphic Converter does open the Zone files on DVD 2, but of course the images are huge, and geocoding the bits you can save out of the file looks like it would be tedious. More investigation required...

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!

22 August 2007

Hosting Google Maps in your web pages

Looks like I can now easily host Google Maps on my own pages by simply cutting and pasting some code.

View Larger Map

When you are looking at the map you want to include in your web page at http://maps.google.com/, click Link to this page and copy the html in the second text box. Paste it into your web page and away you go.

09 August 2007

Maps data moved to .Mac

I've moved all my tracks and photos from my old impty website to .Mac, since Apple has increased the storage available for the account, and it's simple to buy more space if I need it. The new version of iPhoto also gives a great way of showing photos, including full-size downloads of photos. With the new iWeb, I can apparently include Google Maps in iWeb pages: I'll see if the kml files can be made to work so I can integrate all the bits together in the one place.

Here are the previous tracks:
  1. Pinnacle walk 6 June 2007.
  2. Wee Jasper Hume and Hovell recce 16 June 2007.
  3. Big Hole recce 30 June 2007.
  4. Big Hole Marble Arch 22 July 2007. Tiny url: http://tinyurl.com/357phd.