[postgis-users] Merging Contour tables in PostGIS

[Max Bott]

Hi All,

I have 2 tables (contours1 & contours2) in my postgis database which I have
populated from shapefiles containing contours in adjacent geographic areas.
These 2 tables contain (amongst other things) the following columns

"ELEVATION" double precision,
the_geom geometry

To create my merged table covering the contours from both contours1 and
contours2 I used

SELECT a.ELEVATION,ST_LineMerge(ST_Collect(a.the_geom, b.the_geom)) AS
the_geom
INTO merged_contours
FROM
contours1 AS a,contours2 AS b
GROUP BY ELEVATION;

but that gave the result

********** Error **********

ERROR: column a.elevation does not exist
SQL state: 42703
Character: 8

Any ideas?

Cheers,
Max

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