+MattWhitney Posted February 18, 2013 Share Posted February 18, 2013 While trying to hide a cache in Shunyi, China (suburb of Beijing) tonight, I checked my coordinates multiple times. But, when I went to Geocaching.com to validate the coordinates on the map, they all turned out wrong (far to the East and a little to the North.) Yet, when I checked the same coordinates against the map view (in Google maps) and the map and satellite view (on ditu.google.cn) the coordinates plotted correctly. The satellite view on US Google maps was also wrong (same location as the Groundspeak map.) I'm worried about trying to activate the cache if the Groundspeak map is showing my coordinates in the wrong location; even though I know the coordinates are right using GPS + GLONASS and two other online map sources. While I have a request into Geocaching.com for guidance on the issue, I think it's president's day back home so they may be off. If anyone is reviewing this forum and familiar with this issue, I'm happy to know what you think. For all I know the issue of representational inaccuracies related to China has been an old topic here on the forum. If not and I'm the first, maybe I've brought up something that needs fixing. Thanks for reading. Looking forward to guidance on my next step in placing this cache. Thanks Matt Whitney Quote Link to comment
+Gitchee-Gummee Posted February 18, 2013 Share Posted February 18, 2013 One should never put (much) faith into online maps. They are nothing more than overlays. Two reasons that the guidelines say to use a GPSr to obtain coordinates for placements -- One) That first line in this post; Two) Other folks will also (supposedly) be using a GPSr to find those coordinates. Regarding reason two, why would you want to use map coordinates that do not align with the GPSr coordinates? Obviously, it wouldn't do any good for anyone. They'd never find the cache. Trust your garnered readings far more than those transferred to a bunch of overlays. That said, you really ought to check that your unit is using WGS-84 and HDD(D)° MM.MMM Datum and Format, it never hurts to check it again. Stuff happens. Quote Link to comment
+MattWhitney Posted February 18, 2013 Author Share Posted February 18, 2013 One should never put (much) faith into online maps. They are nothing more than overlays. Two reasons that the guidelines say to use a GPSr to obtain coordinates for placements -- One) That first line in this post; Two) Other folks will also (supposedly) be using a GPSr to find those coordinates. Regarding reason two, why would you want to use map coordinates that do not align with the GPSr coordinates? Obviously, it wouldn't do any good for anyone. They'd never find the cache. Trust your garnered readings far more than those transferred to a bunch of overlays. That said, you really ought to check that your unit is using WGS-84 and HDD(D)° MM.MMM Datum and Format, it never hurts to check it again. Stuff happens. Totally agree all- was just worried about proceeding if I knew the GC.com map was not registering it's overlay correctly. I'm only too happy to drive on as if the map issue was not an issue given the GPSr. Yes, the data format is correct- but thank you for helping me remember to verify that. Thanks for your insight! Matt Quote Link to comment
+Tikketiimi Posted May 19, 2013 Share Posted May 19, 2013 Came across with the same problem; the Web map overlay (or caches) is shifted, so that the caches appear about 500m west from their real location. It seems to be systematic problem at least in east Beijing area. Quote Link to comment
+ncambray Posted August 4, 2013 Share Posted August 4, 2013 Here in Shanghai, caches seem to be shown about 250m northwest of their true location. But using the offline OSF maps on my Android phone they are spot on Quote Link to comment
+Nezgar & Vana Posted August 28, 2013 Share Posted August 28, 2013 (edited) While trying to hide a cache in Shunyi, China (suburb of Beijing) tonight, I checked my coordinates multiple times. But, when I went to Geocaching.com to validate the coordinates on the map, they all turned out wrong (far to the East and a little to the North.) Yet, when I checked the same coordinates against the map view (in Google maps) and the map and satellite view (on ditu.google.cn) the coordinates plotted correctly. The satellite view on US Google maps was also wrong (same location as the Groundspeak map.) The chinese government requires unlicensed map providers to mangle their map data slightly, usually with offsets of 100-300 metres... Its not geocaching,com, its google... China has had a little bit of a war with google since 2010. Even Garmin maps of china for your GPS have this issue. If you buy a GPS unit in china, they supposedly have some code on them to 'correct' the offset maps. Many cel phones have additional software installed to 'correct' the maps, and lots of people complain about the messed up maps when they remove said software from their phones. I was in china a few years ago and also noticed this not just for geocaching, but for other online research looking at various map providers in the course of our travels. Thankfully, the satellite imagery is OK. OpenStreetMaps are also OK, as the data is user-created. I used OSM on the Garmin GPS too, which was accurate and free, although with the amount of development going on in the country, a lot of non-urban areas are incomplete. Check out the long running threads on some google forums about this too: http://productforums...aps/zVmRao1Im3w So just trust the coordinates and you should be good on the ground! Edited August 28, 2013 by Nezgar & Vana Quote Link to comment
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.