[OSM-dev] QA, check for tag change

[Frederik Ramm]

Hi,

On 10/2/19 20:36, yves wrote:
> What would be a cheap way to find ways that once were highway=* and are
> now a piste:type=nordic but no more a highway=* ?

Define "cheap" ;)

I usually tackle issue like this with a contraption of history file,
osmium, and a script in a programming language of choice (for easy cases
even shell script works).

The first step is to have osmium convert the history file into "OPL"
format which gives you one ascii text line for every version of an
object, neatly sorted by type, ID, and version:

osmium cat somefile.osh.pbf -tway -fopl

>From there, the following Perl script would for example solve your problem:

#!/usr/bin/perl

use strict;

my $lastid;
my $was_highway;
my $lost;

while(<>)
{
    /^w(\d+) .*T(\S+)/ or next;
    my ($id, $tags) = ($1, $2);
    my $piste = ($tags =~ /piste:type=nordic/);
    if ($id eq $lastid)
    {
        $lost = ($piste && $was_highway && $tags !~ /highway=/);
    }
    else
    {
        print "way $lastid lost its highway tag\n" if ($lost);
        $lastid = $id;
        undef $was_highway;
        undef $lost;
    }
    $was_highway = $was_highway || ($tags =~ /highway=/);
}

save that in foo.pl and simply do a

osmium cat somefile.osh.pbf -tway -fopl | perl foo.pl

You will find that it is a bit rough around the edges, e.g. it doesn't
correctly handle deleted objects and disregards the very last way in the
file, but it works *in general*.

Bye
Frederik

PS: Slightly more sophisticated Perl snippets from some of my scripts
lying around include

while(<>)
{
    my $part;
    my @parts = split(/ /, $_);
    my $obj = shift(@parts);
    foreach (@parts)
    {
        $part->{substr($_,0,1)}=substr($_,1);
    }

(this splits the OPL line into a hash that you can then access with
$part->{'v'} for the version, $part->{'T'} for the tags etc.etc.) and

    my @tags = split(/,/, $part->{'T'});
    my $tag;
    foreach (@tags)
    {
        /(.*)=(.*)/;
        $tag->{$1}=$2;
    }

which further splits the "tags" part into a hash with tags so that you
can then write code like "if defined $tag->{'highway'}" etc.


-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"