Comparison between distances from the ccm and our calculated distances

[cedric]

Nos distances sont écrites dans la base CCM table riversegments
Ci dessous une requete pour les comparer

select cum_len_sea,len_tom from rivernodes
 inner join riversegments on riversegments.tonode=rivernodes.id 
limit 100

select count(*) from(
select cum_len_sea,len_tom from rivernodes
 inner join riversegments on riversegments.tonode=rivernodes.id 
where cum_len_sea != len_tom) as sub
-- 30384

select count(*) from(
select cum_len_sea,len_tom from rivernodes
 inner join riversegments on riversegments.tonode=rivernodes.id 
where cum_len_sea != len_tom) as sub
-- 86380

C'est vraiment curieux quand on regarde du plus près

select cum_len_sea -len_tom as diff from rivernodes
 inner join riversegments on riversegments.tonode=rivernodes.id 

select count(*),diff from(
select cum_len_sea -len_tom as diff from rivernodes
 inner join riversegments on riversegments.tonode=rivernodes.id ) as sub
group by diff

count	diff (m)
4	-87532
6	-57127
30338	-26407
36	-11560
86380	0

Table pour carte de comparaison

drop table if exists tabledistance;
CREATE TABLE tabledistance AS(
select cum_len_sea-len_tom as diff, rivernodes.the_geom from rivernodes
 inner join riversegments on riversegments.tonode=rivernodes.id 
where cum_len_sea != len_tom);
alter table tabledistance add column id serial;
drop table tabledistance;