Thread: Garmin China City Navigator NT 2012.20 CH (Official shifted+Venus non shifted)

Originally Posted by syzygy

As far as I know, there is no special chipset required. f and g are implemented in the navigation application (firmware or executable file) or plugin like 006B082300.bin today, probably to save cost. Of course, this makes it easier to reverse-engineer the f and g.

You are right. My first information seems to be a little outdated.
Can you confirm that on governemental request routing is allowed to use correction algorithms (under NDA), but mapping must be left offsetted?

Originally Posted by syzygy

May be. Each Venus release in China has the following disclaimers which I did not bother to post here.

* There is certain risk to use maps in this series. Think thrice before using it.
* There is no warranty or guarantee provided for using maps in this series. Please bear the consequences by yourself.
* Maps in this series are for research and education purposes. Please delete the files in 24 hours after downloading.
* Please consult your lawyer beforehand for all legal issues regarding the use of shift-corrected maps.

1-3 :-)
4: I did. The answer was a little bit like 1-3. He told me that in China things can be of legal issue without being explicit forbidden. So there would be a risk in doing anything not being explicit allowed. Is this interpretation right?

Originally Posted by Quarktasche10

Can you confirm that on governemental request routing is allowed to use correction algorithms (under NDA), but mapping must be left offsetted?

Not sure what do you mean by correction algorithm? The official map itself is never corrected. Instead, the coordinates received from the GPS chipset are added by the same amount of shift (i.e. the same x'=f(x, y) and y'=g(x, y) transformation) to match the shifted map. As a result it appears no shift to the user, but the recorded track will have shifted coordinates (well, newer devices provide both coordinates before and after the addition now). The code to do the transformation is written and compiled by the government then licensed to the GPS device maker.

Originally Posted by Quarktasche10

4: I did. The answer was a little bit like 1-3. He told me that in China things can be of legal issue without being explicit forbidden. So there would be a risk in doing anything not being explicit allowed. Is this interpretation right?

I am not a lawyer, but that's the common interpretation.