added export scripts for ortho and buildings

export_heightmaps.py

@@ -18,6 +18,20 @@ os.makedirs(OUT_DIR, exist_ok=True)
 gdal.UseExceptions()
 
 
+def build_dgm_vrt_if_needed():
+    """Build the DGM VRT automatically when missing."""
+    if os.path.exists(VRT_PATH):
+        return
+    tif_paths = sorted(glob.glob(os.path.join(RAW_DIR, "*.tif")))
+    if not tif_paths:
+        raise SystemExit(f"No TIFFs found in {RAW_DIR}; cannot build {VRT_PATH}.")
+    print(f"Building {VRT_PATH} from {len(tif_paths)} GeoTIFFs...")
+    try:
+        gdal.BuildVRT(VRT_PATH, tif_paths)
+    except RuntimeError as exc:
+        raise SystemExit(f"Could not build {VRT_PATH}: {exc}") from exc
+
+
 def open_dataset(path, purpose):
     """Open a dataset and fail fast with context."""
     try:
@@ -57,7 +71,8 @@ def cleanup_aux_files():
     print(f"Cleanup removed {removed} temporary files/sidecars.")
 
 
-ds = open_dataset(VRT_PATH, f"Could not open {VRT_PATH}. Did you run gdalbuildvrt?")
+build_dgm_vrt_if_needed()
+ds = open_dataset(VRT_PATH, f"Could not open {VRT_PATH} after attempting to build it.")
 
 band = ds.GetRasterBand(1)