GPS resolution

As Randy has tried to use his new Garmin GPS in China, we have noticed that most of the time, our position was off-set. We have often been off-roading or driving right through a reservoir, according to the display and our coordinates.

We were, of course, disappointed, especially since in the US this particular system worked beautifully, and we've seen several people use Chinese GPS systems here without a problem. Randy researched Googled around and found a GPS user site that discussed this very problem. According to one poster, "The issue exists in the way the information was provided to us by the Chinese government. Due to their regulations, mapping information sent out of China must be shifted slightly compared to the actual layout of their grid mapping." Another pointed out that a .bin file was omitted from the Chinese map package.

With this information, Randy contacted Garmin directly, describing the problem (which, gaging from the one user site, must be a frequent complaint). He requested a fix for this offset problem. The first email he got back from Garmin was really strange. Instead of a fix, the customer service person emailed back offering to help us return it for a refund. Randy emailed again, irritated that instead of fixing this problem their solution was for us to return the unit. Another response came, this time with a better description of the reason why we have this offset, and the file that will correct it. According to Garmin:
Due to requirements by the government of China, City Navigator China NT mapping is shifted by several hundred meters unless you are physically located within the borders of China and your compatible Garmin device has acquired a satellite signal. While using your Garmin device within China, the unit will compensate for the shift in the mapping and will both navigate and mark waypoints correctly. In order for this "unshifting" to be done correctly, the unit relies on a .bin file located on the Garmin unit and/or datacard.

Once Randy transferred that file to his SD card with the China maps, the offset has (so far) seemed to disappear.

Comments

Anonymous said…
On the otherhand, my GPS wants me toake left turns off bridges i Pittsburgh! Aunt Snoozie
eulogos said…
This is so odd. China is trying to prevent people outside from being able to pinpoint certain targets too accurately. But do they think the other governments of the world rely on Garmin or on Google maps? The US government has satellite topo maps way more detailed than anything on the internet. China can't prevent the taking of pictures from satellites.
So this shift a few meters thing is just a knee jerk information protection reaction, as far as I can see. Maybe there is some aspect to this I haven't considered. Maybe they are thinking of two bit terrorism rather than other world governments.
Susan Peterson
globalgal said…
Did you know it is illegal to survey or make maps in China? Maps are a real problem for our flight school - the maps we were able to get were really old and out of date! We ended up creating our own using Google Maps, which is not ideal, as you can imagine!
Jen Ambrose said…
Well, Susan, in some ways it makes sense to me that any country wouldn't want you to access that level of detail of city streets, highways, and landmarks unless you are phyisically within that country's jurisdiction. Just the fix was so odd, that we had to contract Garmin ourselves, request the fix, and then our position would be correct. Of course, some of that, too, might be Garmin's way of protecting their unique IP as well.

Global Gal--I have read that, too. What makes that so wild is the level of detail you can get on Google Earth. For many places in China the detail is much better than in the US! Remember the residence of the Vice President of the US was concealed on Google Earth, and yet on some of the latest images from China you can distiguish windows on buildings!