lat() and lon() fail for points outside of a convert statement

[ryanfae]

makeing a point (with pt(eval, eval)) creates a geometry with a coordinate pair inside of it. For convert statements, lat() and lon() obtains the latitude and longitude from that coordinate pair, like so: https://overpass-turbo.eu/s/1PTS

But for non-convert statements attempting to use lat() and lon() directly, like next to an around clause, it fails and instead returns (0, 0): https://overpass-turbo.eu/s/1PTU

The expected behavior is to return 40 (or a float variant) from lat() and -80 (or a float variant) from lon(), and for nwr(around:20, lat(), lon()); to find nodes, ways, and relations within 20 meters of (40, -80).

[mmd-osm]

The reason why this doesn't work is that around expects actual lat / lon values, rather than an "evaluator". Both lat() and lon() are examples of an evaluator. You can only use them in statements that explicitly support them, like the first example you've mentioned (pt(eval, eval)). Please refer to the documentation for further details.

[ryanfae]

Ah, I see.

May I ask why that's a restriction? That seems to stop any conversions between nodes and pts (and thus ways and lstrs, and relations and polys), unless I'm missing something in the docs, which could be useful in cases of drawing linestrings and polygons based on existing OSM data.

It also prevents one potential use of Overpass for geolocation of images, which is what I use it for outside of mapping. The inability to reference pts outside of a geometric context, like with around, means that additional coordinate data obtained from other sources cannot be used in supplement to the existing OSM data Overpass provides an interface for. I can provide a full example if this explanation doesn't make sense.

[mmd-osm]

Well, since you're anyway working with external data, you could easily rewrite your example as nwr(around:20, 40, -80);out geom;. There's really no need to use pt here.

[ryanfae]

That's true, but it gets really painful to work with past a point.

Let's say I wanted highways within 20 meters of a list of hundreds of coordinates—(40, -80), (50, -100), and so on. I'd need to write nwr["highway"](around:20, 40, -80);, then nwr["highway"](around:20, 50, -100);, and then again for every pair in the list. This is doable (with a few key combinations) in any modern text editor, but then if I need to change that query at all, I need to change it in every line, a task that involves cutting the text out of something like Overpass Turbo, doing some find-and-replace query, re-copying and re-pasting it, and tabbing it back in for style. It becomes really annoying when done frequently.

Being able to 'store' those values, as the ability to reference between pts in around statements would allow, makes this much easier: Just throw the pts in a set and foreach over them. The repeated text is minimal (5-6 characters), and the main query only has to be typed once for easy reading.

[mmd-osm]

Well, around also supports a lists of lat/lons, for a use case that sounds like you want to download objects along some virtual way. See https://www.openstreetmap.org/user/mmd/diary/42055 for a few examples. In general, I'd recommend to generate queries using code (like Python, Javascript or whatever works for you). Copy and pasting in overpass turbo will probably be a huge time sink. Better directly talk to Overpass API from your code.

[ryanfae]

Oh, that's amazing! Both of those solutions are useful to me and remedy the latter issue. Thank you!

(For what it's worth, I still think that node to pt conversion (and everything it implies) would be useful if it's easy to implement, but it's not something I personally use.)