[OpenLayers-Users] Shifting a layer

[Eric Jarvies]

What Tyler suggests, is likely the problem.  I have the same issues  
here in Mexico.  The US, IK, etc., are al very well mapped, which is  
to say, so many third party resources utilize the maps in these  
regions, that over time Google has corrected their raster/vector  
sources.  About 2 months ago, Google implemented street level maps for  
Mexico and most of central/south america.  First they start with  
maps.google.com, and then mobile maps, and lastly they populate Google  
Earth. At this point, they have not yet included Mexico into Google  
Earth.  During this time, the Mexico street level maps have been  
changed 4 times(that I know of), which is to say I noticed the maps  
were offline for a period of time(hours, sometimes days), and also  
noticed position changes across the entire territory, as well as  
segmented changes.  These changes have resulted in sometimes the  
street-level maps being 4 meters to the east of where satellite images  
show the roads, and then 3 meters to the south/west, and so on.  Over  
time they continue making improvements, and depending on the community  
activity of the region, so depends the timeliness and accuracy of the  
improvements.

I have had to create intentionally inaccurate maps in order to adjust  
for Google's road positions, so the resulting vector overlay's would  
be in-line with Google's Satellite street locations.

Eric

On Jan 15, 2008, at 7:31 AM, Tyler Erickson wrote:

> In my neck of the woods, the current imagery displayed by Google  
> Maps and Google Earth imagery are shifted about 10-20m to the east.   
> You can see this when you compare the Google Maps streets data to  
> the satellite view (see the following URL).  I have noticed the same  
> thing when uploading GPS data that I collected on the local trails  
> that are visible in the imagery.
>
> So its possible that is nothing wrong with your WMS layers, but it  
> is that the Google Maps imagery in your area is not precisely  
> registered...
>
> Example:
> http://maps.google.com/maps?f=q&hl=en&q=ann+arbor,+mi&ie=UTF8&t=h&om=1&ll=42.307451,-83.739821&spn=0.005094,0.009656&z=17
>
> - Tyler
>
>
> Cranio wrote:
>>
>> Yes I do use that projection. I don't know if my WMS layers (that I
>> superimpose on Google) are wrong,
>> altough they shouldn't (they come from governative sources).
>>
>> Anyway, the WMS are *not* in S-Mercator, but I think they're  
>> reprojected
>> correctly.
>>
>>
>> Christopher Schmidt-4 wrote:
>>
>>> On Tue, Jan 15, 2008 at 01:42:29AM -0800, Cranio wrote:
>>>
>>>> Hi.
>>>>
>>>> another question. My google layer, when greatly zoomed, appears  
>>>> to be
>>>> lightly shifted in
>>>> respect to the WMS ones, a shift of about 10-20m in Latitude and  
>>>> 5-10m in
>>>> Longitude.
>>>>
>>>> Is there a way to put an offset somewhere to achieve a perfect
>>>> alignment?
>>>>
>>> No.
>>>
>>> Are you using Spherical Mercator? There shouldn't be any shift...
>>>
>>> Regards,
>>> -- 
>>> Christopher Schmidt
>>> MetaCarta
>>> _______________________________________________
>>> Users mailing list
>>> Users at openlayers.org
>>> http://openlayers.org/mailman/listinfo/users
>>>
>>>
>>>
>>
>
>
> -- 
> Tyler A. Erickson, Ph.D.
> Research Scientist
> Michigan Tech Research Institute
> 3600 Green Court, Suite 100
> Ann Arbor, MI 48105
> tyler.erickson at mtu.edu
> www.mtri.org
> www.michiganview.org
> _______________________________________________
> Users mailing list
> Users at openlayers.org
> http://openlayers.org/mailman/listinfo/users

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