[postgis-users] Length of a line above polygon

[Matej Mailing]

Hi,

Thank you for the answer. However, I don't get the right result. For
example, when there is a line that is long 500 meters and it crosses 5
polygons (on each of them maybe just a meter or few meters, except one
where lies a majority of the line), I get the full length of the lines
for corresponding polygons - i.e. as every polygon that is crossed is
crossed by the total line length. What I want to get is the actual
length of the part of the line that crosses every specific polygon.

TIA,
Matej


2012/7/3 Denis Rouzaud <denis.rouzaud at gmail.com>:
> Hi,
>
> You can use something like
>
> SELECT areas.id, SUM( ST_Length( lines.geometry) ) FROM lines,areas WHERE
> ST_Intersects(lines.geometry,areas.geometry) GROUP BY areas.id ;
>
> Greetings,
>
> Denis
>
>
> On 07/03/2012 01:36 PM, Matej Mailing wrote:
>>
>> Hi all,
>>
>> We have a layer that contains polygons and another that contains lines
>> that lie on them. Parts of the lines are laying "inside" the polygons
>> and I would like to get a sum of all the lengths of lines that lie on
>> the polygons. What is the easiest way to achieve this?
>>
>> TIA,
>> Matej
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>
>