--- a/gdalwarp.txt	Wed Aug 25 08:45:36 2021 -0700
+++ b/gdalwarp.txt	Thu Aug 26 08:37:46 2021 -0700
@@ -6,3 +6,10 @@
 There does not seem to be a good, easy way to tell it to preserve
 resolution.  You must play with -tr. Anything higher than 1x1 is nasty
 and coarse. Anything less gobbles disk space exponentially.
+
+Another alternative: just drop gdalwarp and for each raster layer, set
+Properties... Additional no data value to 0. Import via the following
+procedure:
+
+http://www.qgistutorials.com/en/docs/raster_mosaicing_and_clipping.html
+http://www.qgistutorials.com/en/docs/3/raster_mosaicing_and_clipping.html