Describe the feature or enhancement you're looking for
A common way to create GCPs is to place points at the center of intersections in both the Sanborn image and the map in the georeferencer. Typically you place matching points at the centers of the intersections. The center is usually easy to find on the OSM map, which is schematic. But it can be less obvious on the Sanborn map, where the intersection is a correctly-scaled rectangle.
I'd like some tool to drag a rectangle on the Sanborn image, and have it place a point in the exact center of that rectangle. Finding the two corners of the intersection is easy because there's ink there. Finding the center is less easy because it's often blank.
If this request is linked to a problem, please describe.
Placing a point in the center of the intersection involves eyeballing, which can generate suboptimal fits.
Describe alternatives you've considered
If parcels are available and the same blocks still exist, it's easier to place GCPs on the corners of the parcels.
Sometimes the Sanborn map has dotted lines around the center of the intersection, I think indicating water mains. These can be used to find the center.
Additional context
For example, on Washington, D.C. 1916 Vol 2 p161, the NORTH CAPITOL intersections on the right are all large rectangles. They all have dotted lines in them, but they aren't quite in the center of the intersection:
Describe the feature or enhancement you're looking for
A common way to create GCPs is to place points at the center of intersections in both the Sanborn image and the map in the georeferencer. Typically you place matching points at the centers of the intersections. The center is usually easy to find on the OSM map, which is schematic. But it can be less obvious on the Sanborn map, where the intersection is a correctly-scaled rectangle.
I'd like some tool to drag a rectangle on the Sanborn image, and have it place a point in the exact center of that rectangle. Finding the two corners of the intersection is easy because there's ink there. Finding the center is less easy because it's often blank.
If this request is linked to a problem, please describe.
Placing a point in the center of the intersection involves eyeballing, which can generate suboptimal fits.
Describe alternatives you've considered
If parcels are available and the same blocks still exist, it's easier to place GCPs on the corners of the parcels.
Sometimes the Sanborn map has dotted lines around the center of the intersection, I think indicating water mains. These can be used to find the center.
Additional context
For example, on Washington, D.C. 1916 Vol 2 p161, the NORTH CAPITOL intersections on the right are all large rectangles. They all have dotted lines in them, but they aren't quite in the center of the intersection: