TopoRama

Georeferencing the toporama images

All images are in unprojected geographic space. 1:250,000: most images are 3200 x 1600 pixels, covering 2 x 1 degree, 1 pixel 0.000625 decimal degrees. 1:50,000: most images are 3200 x 1600 pixels, covering 0.5 x 0.25 degrees, 1 pixel 0.00015625 decimal degrees ( See http://toporama.cits.rncan.gc.ca/En/coord_system.html for full details).

make-index.aml, a quick and dirty ArcInfo script to create worldfiles for toporama images:

1. ) project yt-250k and yt-50k index covers to geographic DD
2. ) extract coords for each tile (by putting each neatline to a separate cover and describing)
3. ) build worldfiles for each
4. ) build a download list file

The results: yt-toporama.zip

Notes: The worldfiles may not be correct for images north of 68 degrees. Not all of the 50k images will be available on the toporama server. The index covers used by the aml can be downloaded from GeomaticsYukon's ftp site under 'Base_Information'.

Also see DRGMapCal by Dave Patton, the program will generate tfw files for any Toporama image, and does it correctly regardless of the image's pixel size, or the latitude.

 

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13 Jan 2006 bugfix world files are oriented from top-left not bottom-left. I was reversed. Thanks to Dave Patton for reporting and diagnosing the bug. make-index.aml is fixed but the downloadable worldfiles are not. Consequently the images will load in the right place, but are flipped upside down. To fix subtract 0.7501562475 from line 6 of each file.

 

 

I	Attachment	Action	Size	Date	Who	Comment
aml	make-index.aml	manage	2.7 K	2006-01-13 - 16:15	MattWilkie	quick and dirty ArcInfo script to create worldfiles for toporama images
zip	yt-toporama.zip	manage	163.3 K	2004-05-12 - 09:51	MattWilkie	worldfiles and download list for toporama images within the Yukon