Creating polygons with fixed extent based on point which represents S/W corner using QGIS
In QGIS, use "Geometry by Expression" tool (in a projected CRS). It will also add points information/attributes to polygons.
Select "Polygon" as "Output geometry type" option.
Add the following expression as "Geometry expression" value:
make_square(make_point($x, $y), make_point($x+100, $y+100))
Using a Virtual layer, you can create a polygon of the desired dimension and move it to each location of the point layer. You can then
save as the output if you want to persist the data.
Go to the menu
Layer > Add Layer > Add/Edit Virtual Layer... and enter the following query. Replace the layer name for yours.
WITH src AS ( SELECT ST_GeomFromText('POLYGON((0 0, 100 0, 100 100, 0 100, 0 0))') AS geometry ) SELECT ID, ST_Translate(src.geometry, st_x(pt.geometry), st_y(pt.geometry),0) as geometry FROM "myPointLayer" pt, src
For each point (x,y) in a projected CRS generate a string like:
polygon((x y, x+100, y, x+100, y+100, x y+100, x y))
you can then process that into a
Then save the layer as a shapefile (or better still a GeoPackage).