[Talk-ca] canvec data offset

[michael bishop]

i wrote a josm plugin that does all the math and marks the border of 
every canvec tile
some of the tiles match my grid perfectly, and match eachother with no 
overlap or gap
other tiles are offset slightly and dont fit the grid or eachother

by checking the grid in my plugin, i can tell which node is in the 
'correct' spot, because the canvec edges are always a certain fraction 
of a degree


On 01/30/2012 06:36 PM, Samuel Longiaru wrote:
>
> But which is the "right"position?  When one is given to be 3 cm's off 
> the other, neither is more accurate, given the data collection 
> technique.  I think you are beyond the accuracy of the data themselves 
> at that level.  While merging and then combining a stream or a road 
> that crosses a tile boundary, trying to decide which node is more 
> "accurate" is one of those questions best asked only during periods of 
> intensive navel contemplation.  Take either one.  The precision of the 
> data exceed  their accuracy I would guess by several orders of 
> magnitude.  Is the next node along the way mapped to 3 cm accuracy?  
> Or the next, or the next?  No.  Here is an example where "good enough" 
> is TRULY "good enough".  It's all the science can bear.
>
> Sam
>
>
>
> -----Original Message-----
> *From*: michael bishop <clever at nbnet.nb.ca 
> <mailto:michael%20bishop%20%3cclever at nbnet.nb.ca%3e>>
> *To*: Talk-CA OpenStreetMap <talk-ca at openstreetmap.org 
> <mailto:Talk-CA%20OpenStreetMap%20%3ctalk-ca at openstreetmap.org%3e>>
> *Subject*: Re: [Talk-ca] canvec data offset
> *Date*: Mon, 30 Jan 2012 18:01:04 -0400
>
> yeah, thats what i had to do for every node
> but part is the issue there, is that when i merge 2 nodes, it doesnt 
> always go to the 'right' position'
> need to manualy select them in the right order to make it go in the 
> right direction, it seems more like an error in the canvec data then 
> an extra step i need to do on every tile
> almost looks like floating point rounding errors, but not sure why 
> some tiles are ok and others arent
>
>
> On 01/30/2012 05:56 PM, Samuel Longiaru wrote:
>>
>> Have you tried just zooming back a bit in JOSM and merging them?  
>> It's part of my stitching process for each tile.  I've never had a 
>> merge refused because of a 3 cm difference (but, of course I've never 
>> looked that closely to see how far apart they were actually).  We're 
>> dealing with precision here... not accuracy at that level.
>>
>> Sam
>>
>> -----Original Message-----
>> *From*: michael bishop <clever at nbnet.nb.ca 
>> <mailto:michael%20bishop%20%3cclever at nbnet.nb.ca%3e>>
>> *To*: Samuel Longiaru <longiaru at shaw.ca 
>> <mailto:Samuel%20Longiaru%20%3clongiaru at shaw.ca%3e>>
>> *Subject*: Re: [Talk-ca] canvec data offset
>> *Date*: Mon, 30 Jan 2012 17:42:42 -0400
>>
>> yeah, its not much, but its enough to screw up josm when trying to 
>> combine things between the 2 tiles
>> have to fix each node on the border one by one, no real patern to 
>> which direction they are shifted
>> even along a solid line (the edge of the tile), the nodes are going 
>> up&down and zig-zagging across the edge
>>
>>
>> On 01/30/2012 05:31 PM, Samuel Longiaru wrote:
>>>
>>> I can hardly put my finger to my nose to within .03 meters... and 
>>> that's not even drunk.  :)
>>>
>>> Sam L.
>>> Kamloops
>>>
>>>
>>>
>>> -----Original Message-----
>>> *From*: michael bishop <clever at nbnet.nb.ca 
>>> <mailto:michael%20bishop%20%3cclever at nbnet.nb.ca%3e>>
>>> *To*: Talk-CA OpenStreetMap <talk-ca at openstreetmap.org 
>>> <mailto:Talk-CA%20OpenStreetMap%20%3ctalk-ca at openstreetmap.org%3e>>
>>> *Subject*: [Talk-ca] canvec data offset
>>> *Date*: Mon, 30 Jan 2012 17:11:27 -0400
>>>
>>> ive been working with canvec for a few days now, and ive noticed some of
>>> the data is offset by 0.03 meters
>>> its not matching up with nearby tiles
>>>
>>> for example 021O10 doesnt match up with 021O07
>>>
>>> ive noticed the problem on other tiles aswell, but didnt think to write
>>> them down
>>>
>>>
>>> _______________________________________________
>>> Talk-ca mailing list
>>> Talk-ca at openstreetmap.org  <mailto:Talk-ca at openstreetmap.org>
>>> http://lists.openstreetmap.org/listinfo/talk-ca
>>>
>>
>>
>
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