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Guest AcStark

Toporama

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Guest AcStark

I had tried for some time to calibrate the maps I downloaded from Toporama for Ozi, with only marginal sucess. Finally I emailed them and asked if they had UTM coordinates for the corners of the maps. Boy do I feel stupid, of course they do, here's the reply:

 

"Toporama web site provide the upper left corner coordinates in lat and long. The 250k maps are 2 degrees wide by 1 degree high (below the 68 degrees of latitude). 50k maps are 30 seconds wide by 15 seconds high. Toporama also provide the upper left corner coordinates in lat and long. With these parameters may you can make the georeference.

 

If it is not enough you can dowload for free ascii files which contain points coordintate wit a description (attributes). These points are extracted from our NTDB vector files. You can dowload these files from this

web site:

http://ccdi.icdg.gc.ca/

 

We have also an ftp site which contain the corner coordinates of allmost all

our data sets.

ftp://ftp.cits.nrcan.gc.ca/pub/datum/ "

 

I have downloaded and calibrated most of Vancouver Island at 50K now, and will eventually do all of BC unless there is someone out there who want to take on part ofthe job. I know these aren't as good as purchased maps, but they sure beat $850 for the province.

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Guest Goodguys

Its hard to beat Toporama's value!

 

I have most of BC downloaded and mosst of Southern BC calibrated. I've found the maps are somewhat distorted - vertically compressed, so they are not to the same scale horizontally as vertically. I've left my downloaded maps in their compressed state; they still seem to work fine with Oziexplorer. Are you expanding the maps to scale?

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Guest mrgigabyte

quote:
I've found the maps are somewhat distorted - vertically compressed, so they are not to the same scale horizontally as vertically.

 

To display the maps to scale, all you have to do is open them in any graphic app that allows you to independently scale the X and Y components (i.e. Photoshop). Because the images were created with an equal latitude and longitude value per pixel, you must simply scale the X component (longitude) by the cosine of the latitude.

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Guest AcStark

I just leave the maps in the compressed state. Because I have calibrated them that way Ozi works just fine. I have experimented with combining a number of maps into a single file to avoid the problem of running up to the edge, and just jumping to the next map in moving mode. The detail is less on Toporama maps so they are quite a bit smaller and makes the combining possible. (e.g. the 6 map sheets 92b-5,6,11,12,13 combined is only 3/4 the size of 92b11 from Spectrum Digital.)

 

Rather than re-invent the wheel, downloading from Toporama is fast, but if other people have .map files for these it would be great to share them. I can make an FTP site availabe in wanted.

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Guest Goodguys

Thanks, Mr. Gig, for the map-scaling tip.

 

AcStark, as for .map files, I have maps 1 - 16 for 082 e,f,g,j,k,l,m,n, o and 092 f,g,h,i,j and a couple of the k and l (not all 16). Since they are less than 4k each, they are email-able, if you're interested.

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Guest AcStark

Goodguys, thanks for the offer of the .map files. I actually wrote a program to read the data files of corner co-ordinates from:

ftp://ftp.cits.nrcan.gc.ca/pub/datum/ and write out .map files. SO it only took 30 seconds to calibrate the entire province. (after some debugging)

 

It would be nice to correct the shape of the images, but then I would have to manually shrink each one and manually calibrate each one. I think I'll stick with what I have for now. It's nice to know how to correct them though as I may do a few near home I use a lot.

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