[uf-discuss] geo - accuracy of coordinates

Chris Casciano chris at placenamehere.com
Mon Oct 2 16:37:10 PDT 2006

On Oct 2, 2006, at 7:24 PM, Kevin Marks wrote:

> On Oct 2, 2006, at 3:16 PM, Chris Casciano wrote:
>> You could outline any territory as a series of geos if the need  
>> ever arose. But I'm still not clear how we've gotten here. If I  
>> want to say something is in Ireland, or Mexico City or somewhere  
>> in the Alps I'd tag it as such. I thought the original issue of  
>> accuracy was one of precision (either via tool measurement or in  
>> human recollection).
>> Not one of being able to define a "geo" that accurately represents  
>> the floorplan of Yankee Stadium or the whole of Antarctica but of  
>> accurately reflecting if a designation was accurate enough to make  
>> a determination if a specific seat in yankee stadium, "somewhere  
>> in the bleechers", or just "near the stadium as i was walking  
>> around before the game" or "i need to mark the bronx somehow so  
>> left me zoom out and drop a marker from the 50k foot view"
> http://flickr.com/map/? 
> &tag=yankeestadium&fLat=40.828081&fLon=-73.920821&zl=7
> Notice that the yankeestadium tag shows various usages here - the  
> ambiguity between where the photo was taken from and what it was  
> taken of.
> You could probably derive a useful 'centrepoint + radius' for  
> Yankee stadium from the mean and std-dev of those geolocated,  
> tagged points.
> Notice that the URL I used above has 6 digits of latitude and  
> longitude (a supposed precision of ~ 10cm), but a zoom-level  
> parameter to express the actual display I wanted to convey.
> However, what you see is dependent on the size of your browser  
> window, as the zoom-level is defined based on pixel-size, not  
> window width.

I think its also important to note (if you weren't on IRC when this  
came up) that precision in this case isn't only a factor of zoom, but  
also one of someone marking a photo at their location or the subjects  
as well as their accuracy of remembering (or caring to place) the  
location accurately and dropping that very precise marker in the  
proper spot. Mix that with some highly precise data that may come  
from cameras with supplied GPS data and you can see where maybe  
dealing with different size blobs rather then specific points might  
better represent the data.

An interesting discussion all around I think... but do we have any  
sites actually taking any of this into account when users tag  
objects? Did I miss some examples of [at least] taking zoom factor  
into account?

[ Chris Casciano ]
[ chris at placenamehere.com ] [ http://placenamehere.com ]

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