feat: add semantic GIS selection metrics

frontend/README.md

@@ -29,11 +29,14 @@ them explicit. Forest therefore defaults to the official modern 2013-2025
 10 m series, while the separate 1778-1969 historical map series remains
 selectable and is never merged into the same trend.
 
-Selection results use dataset-specific PostGIS summaries. Object layers show
-intersecting counts, population shows inhabitants with partial-sector
-estimates clearly marked and land-cover sources show intersected hectares. The
-advanced workbench remains available but is not required for the primary
-choose-theme, draw-area, read-result flow.
+Selection results use dataset-specific PostGIS summaries with end-user units.
+Building footprints, forest, water surfaces and parcels show intersected
+hectares; roads and linear watercourses show kilometres; population shows
+inhabitants with partial-sector estimates clearly marked. Intersecting object
+counts remain visible as supporting source evidence instead of being the only
+result. Water explicitly explains that volume cannot be derived without a
+reliable depth or bathymetry source. The advanced workbench remains available
+but is not required for the primary choose-theme, draw-area, read-result flow.
 
 The primary workflow is deliberately short: choose a municipality or the complete region, choose a data theme, drag a rectangle on the MapLibre map and read the resulting PostGIS evidence. Releasing the drag runs the active theme query and every other available theme query for the same EPSG:4326 bbox. The result panel shows selection area, exact intersection totals, active-theme density, source identity and bounded feature properties. Map rendering remains capped at 1,000 features while `total_feature_count` reports the exact database count.
 

frontend/src/components/map/MapWorkspace.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useMemo, useState } from 'react'
 import GeoMap from '../GeoMap'
-import type { AreaRead, DatasetCreateResponse, DetectionQaResult, MapViewportState, ProjectRead, QaComparisonResult, VectorSelectionBBox, VectorSelectionResponse } from '../../types'
+import type { AreaRead, DatasetCreateResponse, DetectionQaResult, MapViewportState, ProjectRead, QaComparisonResult, VectorSelectionBBox, VectorSelectionMetric, VectorSelectionResponse } from '../../types'
 import { featureCollectionBounds } from '../../lib/geojsonBounds'
 import { useMapThemeSelectionInsights } from '../../hooks/useMapThemeSelectionInsights'
 import { useTemporalComparison } from '../../hooks/useTemporalComparison'
@@ -222,6 +222,11 @@ function resultMetricLabel(result: VectorSelectionResponse): string {
   return `${result.summary.metric_value.toLocaleString('nl-BE', { maximumFractionDigits })} ${result.summary.metric_unit}`
 }
 
+function selectionMetricLabel(metric: VectorSelectionMetric): string {
+  const maximumFractionDigits = metric.metric_unit === 'inwoners' || metric.metric_unit === 'objecten' ? 0 : 2
+  return `${metric.metric_value.toLocaleString('nl-BE', { maximumFractionDigits })} ${metric.metric_unit}`
+}
+
 function formatTemporalMetric(value: number, unit: string): string {
   const maximumFractionDigits = unit === 'inwoners' || unit === 'objecten' ? 0 : 2
   return `${value.toLocaleString('nl-BE', { maximumFractionDigits })} ${unit}`
@@ -648,6 +653,9 @@ export function MapWorkspace({
   const activeMetricValue = activeSelectionResult?.summary?.metric_value ?? selectedResultTotal
   const activeMetricUnit = activeSelectionResult?.summary?.metric_unit ?? 'objecten'
   const activeMetricLabel = activeSelectionResult?.summary?.metric_label ?? activeTheme.shortLabel
+  const activeSupportingMetrics = (activeSelectionResult?.summary?.metrics ?? []).filter(
+    (metric) => metric.metric_key !== activeSelectionResult?.summary?.primary_metric_key,
+  )
   const activeSecondaryMetric = selectedAreaSquareMetres && selectedAreaSquareMetres > 0
     ? activeMetricUnit === 'ha'
       ? `${((activeMetricValue * 10_000) / selectedAreaSquareMetres * 100).toLocaleString('nl-BE', { maximumFractionDigits: 1 })}% dekking`
@@ -1350,6 +1358,17 @@ export function MapWorkspace({
                       </div>
                     </div>
 
+                    {activeSupportingMetrics.length > 0 ? (
+                      <div className="geo-supporting-metrics" aria-label="Aanvullende gebiedsmetingen">
+                        {activeSupportingMetrics.map((metric) => (
+                          <div key={metric.metric_key}>
+                            <span>{metric.metric_label}</span>
+                            <strong>{selectionMetricLabel(metric)}</strong>
+                          </div>
+                        ))}
+                      </div>
+                    ) : null}
+
                     <div className="geo-theme-results">
                       <div className="geo-results-title-row">
                         <h4>Alle beschikbare thema’s</h4>
@@ -1376,6 +1395,9 @@ export function MapWorkspace({
                 {analysisMode === 'current' && activeSelectionResult?.truncated ? (
                   <p className="geo-data-notice">De telling is volledig; op de kaart en in de tabel worden maximaal {activeSelectionResult.limit.toLocaleString('nl-BE')} objecten getoond.</p>
                 ) : null}
+                {analysisMode === 'current' && activeSelectionResult?.summary?.warning ? (
+                  <p className="geo-data-notice">{activeSelectionResult.summary.warning}</p>
+                ) : null}
                 {mapSelectionError ? <p className="error">{mapSelectionError}</p> : null}
                 {themeResultsError ? <p className="error">{themeResultsError}</p> : null}
                 {temporalComparisonError ? <p className="error">{temporalComparisonError}</p> : null}

frontend/src/styles/app.css

@@ -6135,6 +6135,33 @@ section {
   white-space: nowrap;
 }
 
+.geo-supporting-metrics {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(8rem, 1fr));
+  gap: 0.35rem;
+}
+
+.geo-supporting-metrics > div {
+  display: flex;
+  gap: 0.4rem;
+  align-items: baseline;
+  justify-content: space-between;
+  min-width: 0;
+  border-bottom: 1px solid #e4ebe8;
+  padding: 0.3rem 0.1rem;
+}
+
+.geo-supporting-metrics span {
+  color: #687570;
+  font-size: 0.64rem;
+}
+
+.geo-supporting-metrics strong {
+  color: #263832;
+  font-size: 0.72rem;
+  white-space: nowrap;
+}
+
 .geo-temporal-metrics > div.positive {
   border-color: #b8d8c5;
   background: #f1faf4;

frontend/src/types.ts

@@ -349,9 +349,21 @@ export interface VectorSelectionSummary {
   metric_value: number
   metric_unit: string
   aggregation_method: string
+  primary_metric_key?: string | null
   feature_count: number
   is_estimate: boolean
   warning?: string | null
+  metrics?: VectorSelectionMetric[]
+}
+
+export interface VectorSelectionMetric {
+  metric_key: string
+  metric_label: string
+  metric_value: number
+  metric_unit: string
+  aggregation_method: string
+  is_estimate: boolean
+  warning?: string | null
 }
 
 export interface DatasetTemporalUpdate {