From c5044a1237037464c17e33a898a5635225465de3 Mon Sep 17 00:00:00 2001
From: Markus Metz <markus.metz.giswork@gmail.com>
Date: Sun, 19 Apr 2026 16:09:42 +0200
Subject: [PATCH] read vrt tile only if needed

---
 lib/raster/vrt.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/lib/raster/vrt.c b/lib/raster/vrt.c
index e1bca1c192d..a2ada47495b 100644
--- a/lib/raster/vrt.c
+++ b/lib/raster/vrt.c
@@ -205,8 +205,28 @@ int Rast_get_vrt_row(int fd, void *buf, int row, RASTER_MAP_TYPE data_type)
 #pragma omp critical(raster_vrt_read)
     for (i = 0; i < vrt->tlist->n_values; i++) {
         struct tileinfo *p = &ti[vrt->tlist->value[i]];
+        double tile_west, tile_east;
 
-        if (p->cellhd.north > rows && p->cellhd.south <= rown) {
+        tile_west = p->cellhd.west;
+        tile_east = p->cellhd.east;
+
+        if (R__.rd_window.proj == PROJECTION_LL) {
+            /* longitude wrapping of the tile into the current
+             * reading window */
+            while (tile_west > rd_window->east) {
+                tile_west -= 360.0;
+                tile_east -= 360.0;
+            }
+            while (tile_east < rd_window->west) {
+                tile_west += 360.0;
+                tile_east += 360.0;
+            }
+        }
+
+        /* open the tile only if it overlaps with the current reading
+         * row and the current reading EW extents */
+        if (p->cellhd.north > rows && p->cellhd.south <= rown &&
+            tile_west < p->cellhd.east && tile_east > p->cellhd.west) {
             int tfd;
             void *p1, *p2;