= Distance source =
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{{{
#!sql
alter table ccm21.riversegments add column distance_source numeric;
}}}

The distance source is calculated by the following request :
The distance sea corresponds to the distance of the downstream node of each riversegment
The distance source for a riversegments A is the maximum of the distance + length of the upstream riversegment
Note the upstream catchment function does not return the catchment upstream... so we have to use the upstream_segment function
[[Image(source:data/Docs/trac/upstream_segments_and_catchment.jpg,300)]] 

In the ccm we find the cum_length which is the cumulated length of upstream riversegments but not the distance to the farthest source
{{{
#!sql
select round(max(cum_len_sea+shape_leng) -(select cum_len_sea from ccm21.riversegments where gid =234706)) 
as dist_source from ccm21.riversegments where gid in (select ccm21.upstream_segments(234706));
}}}

The calculation in implemented as method in the ''' BaseEdaCCMRiversegments.r  ''' class and called in ''' main_CCM_France '''




[[Color(,red,Problem :)]][[BR]]
The algorithm stopped at i = 160830 (170828 lines)[[BR]]
"erreur dans if(!is.na(gid)&mtch[i]){ valeur manquante là où TRUE/FALSE est requis"[[BR]]

select cum_len_sea from ccm21.riversegments where gid =381001 --> 794987[[BR]]
select ccm21.upstream_segments(381001)  --> ne renvoie aucune ligne (correspond to a segment in the Basque country in Spain)[[BR]]
	
select round(max(cum_len_sea+shape_leng) -(select cum_len_sea from ccm21.riversegments where gid =381001))as dist_source 
	from ccm21.riversegments where gid in (select ccm21.upstream_segments(381001));  --> renvoie une ligne avec une cellule vide [[BR]]

gid=381001 appartient à zonegeo="France"[[BR]]
J'ai lancé la suite :[[BR]]
distance_source(ccm,silent=TRUE,from=160831)[[BR]]  -->idem

Avec cette requête :--> le gid n'est pas dans la liste[[BR]]
{{{
#!sql
select distinct on (rs.gid) rs.gid  from ccm21.riversegments rs 
inner JOIN ccm21.riversegments rup on rup.tonode=rs.fromnode 
where rs.wso_id in (select wso_id from france.wso where area='France')
order by gid;
}}}

Pour un segment amont, la distance à la source est la longueur du segment.

{{{
#!sql
update ccm21.riversegments set distance_source=shape_leng where gid in(
select distinct on (rs.gid) rs.gid from ccm21.riversegments rs
where rs.wso_id in (select wso_id from france.wso where area='France')
except (	
select distinct on (rs.gid) rs.gid  from ccm21.riversegments rs
	inner join ccm21.riversegments rup on rup.tonode=rs.fromnode
	where rs.wso_id in (select wso_id from france.wso where area='France'))
	order by gid)
}}}