Feat/values at point for line and polygon

[NtnHgr]

Description

Extends the valuesAtPoint endpoint of the GeospatialAnalyzer to accept LineString and Polygon input geometries in addition to Points.
Previously only the value at a single point was returned. Now the values of the underlying raster topics (e.g. ´hoehe_r` of DGM/DOM) can be queried along a line or within an area.

Changes

ValuesAtPointService.handleLogicalRequest now branches by geometry type:

• Point: unchanged, returns a single value.
• LineString: returns a profile.
  • The line is sampled at equal distances (LINE_SEGMENT_LENGTH_METERS, currently 10 m) using ST_LineInterpolatePoint. The first and last point of the line are always included, so the last interval can be shorter than the segment length.
  • The value of every sample point is looked up individually. Since a line can cross several raster tiles, the matching tile is searched per sample point. To keep this fast, the tiles intersecting the whole line are pre-filtered once (candidate_tiles).
  • Output: heights: { min, max, mean, points: [{ index, height }, ...] }. index is the position of the sample point along the line (not a distance in meters). mean is rounded to 2 decimal places.
• Polygon: returns raster statistics in the new property heightStats.
  • The tiles intersecting the polygon are merged (ST_Union) and clipped to the polygon (ST_Clip, cropped to its bounding box). Pixels outside the polygon have no value and are not part of the statistics.
  • Output: heightStats: { count, min, max, sum, mean, stddev } (via ST_SummaryStats). sum and mean are rounded to 2, stddev to 3 decimal places.
  • If the polygon does not overlap the raster coverage, the statistics are empty (null) instead of causing an error.
• All other geometry types are rejected with HTTP 400 and a descriptive message.

As before, one result feature is returned per raster source of the topic (DGM and DOM for hoehe_r).

The segment length (query of LineString) is not an API parameter. It can be changed in one place, the constant LINE_SEGMENT_LENGTH_METERS in general.constants.ts.

Testing

The implementation was tested locally with the PostGIS database.

• Unit tests (values-at-point.service.spec.ts): the generated SQL for Point, LineString and Polygon, one sub-query per raster source, rejection of unsupported geometry types.
• e2e tests (values-at-point.e2e-spec.ts):
  • LineString: response structure, min <= mean <= max, points sorted by index, rounding of mean.
  • Polygon: plausible statistics for both sources, rounding of sum/mean/stddev, only pixels inside the polygon are counted (a triangle covers about half the pixels of its bounding rectangle), polygon outside the raster coverage, unsupported geometry type.
  • Point: existing response structure is unchanged and contains neither heights nor heightStats.

Impact

The existing Point functionality remains unchanged.