Overpass API convert statement

Question

I have read Overpass API by example, but still I am unable to adapt convert statement examples to my need. What I would like to do is to get all marked routes in the area using Overpass Turbo, drop some tags and synthesize some new tags.

My query looks like this:

relation[route][route!="power"][route!="road"]({{bbox}});

out body;
>;
out skel qt;

I would like to:

• add tag color=green when osmc:symbol contains green or when tag kct_green exists
• add tag color=blue when osmc:symbol contains blue or when tag kct_blue exists
• add tag kind as a value of any tags of kct_green, kct_blue, kct_red, kct_green
• remove some tags I no longer need to reduce output file size (like kct_green)

My initial naive attempt is:

relation[route][route!="power"][route!="road"]({{bbox}});

foreach (
  convert rel ::=::,
    ::id = id(),
    color=t["osmc:symbol"]
  ;

  out;
);

out body;
>;
out skel qt;

This kind of works, but lists relations without including their nodes. Moreover, I would like to perform a bit more processing on the color value:

• I want the color to be created only osmc:symbol is present
• I want to extract some information from osmc:symbol to color
• I have no idea how to create the combined value from those kct_green... tags.

I guess I need something more complex, however I have found almost no documentation or examples about convert. Can someone point me in the right direction?

Answer 1

After some experimentation I have found at least a way to add and remove tags:

(
  relation[route][route="hiking"]({{bbox}});
  relation[route][route="foot"]({{bbox}});
  relation[route][route="mtb"]({{bbox}});
  relation[route][route="bicycle"]({{bbox}});
)->.routes;

foreach.routes (
  > -> .w;
  convert rel 
    ::id = id(),
    color=t["osmc:symbol"],
    !complete,
    !destinations,
    !type,
    ::=::
  ->.x;
  (.x;.w;);
  out;
);

out body;
>;
out skel qt;

If I will be able to achieve more, I will update the answer accordingly.