[postgis-users] segmentize lines with order

[Pedro Costa]

Hi Stephen,

Thanks, I was searching some function to change draw order of lines but 
i cannot remembered the postgis function name.
Now I'm trying to do a stored procedure to put the lines in the same order.
Anybody knows some code example that do something like this? I have 
little experience with pl/pgsql and i'm facing something difficult with 
a loop...

Thanks


Em 24-02-2014 18:27, Stephen Woodbridge escreveu:
> On 2/24/2014 11:33 AM, Pedro Costa wrote:
>> Hi guys,
>>
>> I'm trying to use lines from postgis to google maps android.
>> To do that, I'm converting the lines to points with St_DumpPoints and,
>> in gmaps, I make the lines. My problem is that I cannot create a correct
>> sequence to order the points in android and so i get wrong lines (see ss
>> atached). I'm already try to use st_dumpPoints path column and generate
>> a serial but doesn't result.
>>
>> Anybody knows a solution to resolve that?
>
> You probably need to write function that re-orients you lines before 
> you dump them to points. The algorithm is like this:
>
> 1. for the first edge, if the start point match the the start or end 
> of the 2nd edge, if it does then st_reverse() the first edge.
>
> 2. for the rest of the edges, if the edge point of the current edge 
> matches the end point of the last edge, then st_reverse() the current 
> edge.
>
> You might be able to st_union all the edges into one large edge and 
> that should create a new reorder edge.
>
> No you can dump them and the order will be correct.
>
> -Steve
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