feat(analysis): add a Near tool

GEOLIBRE_PARITY.md

@@ -166,8 +166,8 @@ _GeoLibre: docs/features.md › Attribute data and expressions; docs/arcgis-edit
 _GeoLibre: docs/features.md › Processing and analysis; docs/user-guide/processing.md,
 model-builder.md, segmentation.md, obia.md_
 
-- [ ] **Spatial join, intersect, union**. Partial: spatial join, clip, erase, intersect, identity
-  and union are built in; near is missing (_Roadmap: solid ground_).
+- [x] **Spatial join, intersect, union** ([#959](https://github.com/opengeos/RustGIS/issues/959)):
+  spatial join, clip, erase, intersect, identity, union and near are built in.
 - [ ] **More built-in vector tools**: attribute join, merge, extract vertices, points along lines,
   fix/check geometry, random extract, buffer options. Partial (_Roadmap: solid ground_).
 - [ ] **Routing services**: isochrones, service areas, OD matrix, multi-stop routing,

README.md

@@ -99,7 +99,7 @@ Every screenshot is RustGIS itself, rendered offscreen by `cargo run -p rustgis-
 | **Web tiles** | XYZ/TMS/WMS raster tiles, Mapbox Vector Tiles and MapLibre styles (sprites, patterns, expressions), cached and fetched in the background |
 | **Cartography** | Single symbol, unique values, graduated colours, proportional symbols; label classes with SQL queries, straight and curved line placement, installed font families, scale ranges and annotation; stacked and dashed line strokes, symbol levels, reference scales and polygons without fill; masking, display filters, aggregation bins, 2.5D extrusion; graphics and dynamic text |
 | **Editing** | Create, move, rotate, scale, merge, split and explode features; snapping, templates, elevation, traverse, topology rules; domains, subtypes, attribute rules, relationships, archiving; undo for everything |
-| **Analysis** | Selection by attributes (SQL) and location; Buffer, Clip, Erase, Intersect, Identity, Union, Dissolve, Summarize Within, Summary Statistics, Spatial Join, Zonal Statistics, A5 grids and a geometry calculator; viewshed, line of sight, IDW, ordinary kriging, shortest path, suitability modelling; ModelBuilder on a node canvas and scripts with command, parameter and value completion; 1,000+ [GeoLibre](https://github.com/opengeos/geolibre-rust) and Whitebox raster, vector, LiDAR, hydrology and terrain tools |
+| **Analysis** | Selection by attributes (SQL) and location; Buffer, Near, Clip, Erase, Intersect, Identity, Union, Dissolve, Summarize Within, Summary Statistics, Spatial Join, Zonal Statistics, A5 grids and a geometry calculator; viewshed, line of sight, IDW, ordinary kriging, shortest path, suitability modelling; ModelBuilder on a node canvas and scripts with command, parameter and value completion; 1,000+ [GeoLibre](https://github.com/opengeos/geolibre-rust) and Whitebox raster, vector, LiDAR, hydrology and terrain tools |
 | **Imagery** | Ortho and reality mapping, pixel classification (k-means, minimum distance, a trainable neural network), mensuration, hosted imagery tiles |
 | **Layouts and reports** | Page layouts with map frames, legends, scale bars, grids and map series; publication sheets and figures in one command, format panes, guides, snapping and element locks; reports with groups, statistics, charts and subreports; presentations (HTML slideshow, PDF); notebooks (Jupyter in and out) |
 | **Sharing** | PNG export at any DPI; PDF; web map pages, OGC API Features collections, MapLibre styles, glTF scenes, locators; project, map and mobile map packages; offline areas with sync |

ROADMAP.md

@@ -63,7 +63,6 @@ Correct, robust and recoverable, with the foundations other themes stand on.
   administrator can fix for a managed install (no AI Assistant, plugins or web services).
 - Extend the OS keychain secret store to service connections (database passwords, S3 keys,
   AI provider keys and the ChatGPT sign-in's tokens are already kept there).
-- A Near tool beside the overlay tools ([#959](https://github.com/opengeos/RustGIS/issues/959)).
 - Spatial Join by distance, closest, centre in and largest overlap, with merge rules (sum, mean,
   first…) for one-to-one joins ([#851](https://github.com/opengeos/RustGIS/issues/851)).
 - Vector tools, each writing a new layer: join field (a one-off attribute join), merge (append
@@ -219,11 +218,11 @@ Open questions rather than plans; discuss before building.
   templates, elevation, topology; domains, subtypes, attribute rules, contingent values,
   relationships, archiving.
 - Analysis: selection by attributes and location; polygon, lasso and radius on the map; overlay
-  (clip, erase, intersect, identity, union), proximity (buffer) and summary tools, spatial join,
-  zonal statistics, A5 grids, kriging and Calculate Geometry with metric or imperial units; guided
-  workflows (viewshed, line of sight, IDW, shortest path, suitability); ModelBuilder on a node
-  canvas, scripts with command, parameter and value completion, and history copied as code; the
-  GeoLibre and Whitebox suite (1,000+ tools) natively and in the browser.
+  (clip, erase, intersect, identity, union), proximity (buffer, near) and summary tools, spatial
+  join, zonal statistics, A5 grids, kriging and Calculate Geometry with metric or imperial units;
+  guided workflows (viewshed, line of sight, IDW, shortest path, suitability); ModelBuilder on a
+  node canvas, scripts with command, parameter and value completion, and history copied as code;
+  the GeoLibre and Whitebox suite (1,000+ tools) natively and in the browser.
 - Layouts (map frames, surrounds, map series, publication sheets and figures in one command,
   format panes, guides, snapping, element locking and PDF), reports, presentations and
   notebooks; the web app embeddable in a page (`?embed`).

crates/analysis/src/join.rs

@@ -1,6 +1,7 @@
-//! Spatial Join's measures and merge rules: the ground distance between two features, a test that
-//! rules out features too far away to matter, the overlap a feature has with a polygon, and the
-//! rules that roll the values of several matches up into one.
+//! Spatial Join's and Near's measures, and Spatial Join's merge rules: the ground distance between
+//! two features and their nearest points, a test that rules out features too far away to matter,
+//! the overlap a feature has with a polygon, and the rules that roll the values of several matches
+//! up into one.
 //!
 //! Distances are on the WGS 84 ellipsoid, as buffers' are. The nearest points of two features are
 //! found in an azimuthal equidistant plane, centred first between the features and then between
@@ -35,12 +36,18 @@ pub fn first_coord(g: &Geometry) -> Option<Coord> {
 /// in one centred between the pair found, where the plane is true near the answer however large
 /// the features are.
 pub fn distance_m(a: &Geometry, b: &Geometry) -> Option<f64> {
+    let (p, q) = nearest_points(a, b)?;
+    let d = wgs84_distance_m(p, q);
+    d.is_finite().then_some(d)
+}
+
+/// The nearest points (lon/lat) of two features that don't intersect, as [`distance_m`] finds
+/// them: a point of `a`, then one of `b`. `None` for a geometry without a finite coordinate.
+pub fn nearest_points(a: &Geometry, b: &Geometry) -> Option<(Coord, Coord)> {
     // The features' first vertices are a pair of their points: the search starts from them.
     let (fa, fb) = (first_coord(a)?, first_coord(b)?);
     let (p, q) = nearest_pair(a, b, &Aeqd::new(geodesic_interpolate(fa, fb, 0.5)), Some((fa, fb)))?;
-    let (p, q) = nearest_pair(a, b, &Aeqd::new(geodesic_interpolate(p, q, 0.5)), Some((p, q))).unwrap_or((p, q));
-    let d = wgs84_distance_m(p, q);
-    d.is_finite().then_some(d)
+    Some(nearest_pair(a, b, &Aeqd::new(geodesic_interpolate(p, q, 0.5)), Some((p, q))).unwrap_or((p, q)))
 }
 
 /// The nearest points of two geometries (lon/lat) as found in `plane`: a point of `a`, one of `b`.