hello billy, fellow surveyors and my friends: 

when I export cad lines to google earth I am getting an offset error of 5 meter why

why rtk position not matching with google earth?

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Hi Raymond.The issue is to do with the accuracy of the Google Earth imagery. Google Earth imagery is not survey accurate and 5m difference between your RTK shot and features shown on Google Earth imagery is to be expected.



is there any way to make it to 1m accuracy...

Hello Raymond, I don't know much about google earth imagery these depends on what measuring units this is set at when dealing in large coordinates small differences become large. For example when using

U S feet then converting to international feet this is small factor,but in SPCS this can be around 15 feet when this is factor in these large coordinates. I know you work in meters but five meters is about 15 feet.

something likes this could be going on.But this is just a example. And you are dealing with GPS Data to their GPS data. Then again google earth are not in to surveying. It may be like Joel said.There is a lot involve in any kind of  photo imagery when it come to surveying the Army Corps of Engineers here in the us can tell the elevation of the Mississippi River just from satellites photo's But there system is a lot different than google earth. Google is not like a  photo"s taken for surveying .You can only see a certain size object at so many feet, this contain a error in so many feet,when using their scale.

I know it is a lot more accurate than scaling a quadrangle and i did that every time i took a Sun shot .Also in any photo the picture can have distortions because it is looking thru lens that are not flat they are round so only so much of the picture is correct these pictures have to be place like a puzzle to make up one large image Accurate interpretations then lies in a computer making all these photos work into one so it can only be accurate to a certain degree.I have seen sites with Google Earth GPS conversions also Lat. and Long., how accurate they are i do not know,it had the whole world but only conversion in North America.  Hope this help some.


The way i have done it and i am sure there is another way, import your GPS calibration into Trimble Business Center and then import your linework (making sure your TBC job has the correct scale meters or survey feet). You can then export as a KML/KMZ file.
Others have already commented on the accuracy of GE imagery, but did not mention that it varies quite a bit. In some areas I get very good matches.

The other thing to be careful about is choosing your datum and projection. Most of my work is done in NAD83-CSRS(2010) (latest version in Canada) with a UTM projection which is accurate to a few cm. But I have to ensure that I choose the correct settings in my cad program. AutoCad uses EPSG codes and I can choose between 2958 (CSRS.UTM-17N) which seems logical or the traditional UTM83-17 (code 26917). Unfortunately the CSRS version does not work properly (reasons to technical for this post) so I use 26917 and it works well enough. But if I were to choose UTM17 on NAD83 original, I would be out by over 100 metres!

yes, I agree with that. The Chinese google worse than that, more 30 meter difference.

google earth is not a scientific software simply runs a mosaic of images that do not necessarily should be a maximum degree of precision and that if it is the exact point, can the problem is in on google.
at this link there is an article that speaks something about it.



My experience with Google Earth in south america is really good, but you can not expect to much.

There ara zones that can be shifted far as 150 m (localy).

But Google don't use UTM, use Global TM with K =1 in the center meridan.


Hi Raymond

My personal experience exporting osgb36 ostn02 coordinates (UK) achieves much better accuracy than 5M, closer to 0.5M. The key thing for me is to make sure the drawing units are correct, any scale factor inherent to the original coordinate system has been reintroduced and of course to ensure the appropriate coordinate system is assigned to the drawing.

Where are you working? Perhaps the UK grid system is a better fit to the GE projection

Hi Everyone,Raymond is in Saudi Arabia ,but i think a lot of bases has been covered,but there,  is where his work is, the data i have only works for North America.

YES MY FRIEND BILLY AND ALL MY PRECIOUS FRIENDS ,MY COORDINATES ARE IN UTM 0.9996 SCALE ,ZONE IS 37Q ,I AM GETING ERROR OF 6m , I am attached here my kml file friends ,please check it.......I am double checked my data every thing is ok ,is there any way to make accuracy near to 1m ,is there any google earth map calibration like that...........

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