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Garmin TOPO

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A few months ago I found a way to make Garmin's TOPO maps transparent so they showed up on my 60CSX at the same time as City Select. The method was posted here in the forum someplace but for the life of me I can't seem to find the topic any more.

Anyone have any ideas?

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As far as I know, The only way one could make them transparent to edit them and rebuild them. You will need GPSmapEdit and cGPSmapper installed on your computer.


YMMV, use at your own risk, check the EULA prior to proceeding, etc.


There, that should be sufficient disclaimer.


1. find the segment you are looking for. This is time consuming due to the large # of segments. What you can do is take half the files and move them to another folder, open Topo and see if the segment in question still has details. Keep doing that until you isolate the one you are looking for.


2. Open the map segment in GPSmapEdit. Go File-->map properties. In the properties box select the cGPSMapper tab, check the "Map is transparent" checkbox.


3. Next, go file-->export--> cgpsmapper and save it. Rename it the same as the original file. (you may want to have the original saved elsewhere on your computer).


Now I have not tried this myself, but I would think it would lead to ghosting--where you have the same road that is slightly off because it is drawn differently.

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Just note that Polygons are never transparent... So things like lakes and parks will not appear transparent and you will not see anything below them. ONLY the background becomes transparent. All objects are drawn on top of the other maps.

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Obviously I have not heard about such a nifty program (Obviously because of my previous post above).


Just in case you are interested what it does to your file:


It searches the file for a string "GARMIN TRE". The string is preceded by two bytes. The address of the first byte is always a multiple of 16 bytes. Thus it is easy to find with a hexeditor. Using this address as a base there is a bit field of 1 byte size at offset 0x3F.


Bit 1 (0x02) will set your map transparent.


And if you use the same base but offset 0x0D bit 7 (0x80) will mark a locked map.



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