1. The Saxe Gotha overlay (Red) is scaled based on the chain measurements on the survey and the alignment is done with the pond and canal in the northern part of the survey and the outline of the Congaree river on the east side of the survey. It might be good to do another overlay whle aligning with the creeks in the south-western part of the survey.
2. The Granby map (overlay in Blue) did not have a scale. It was re-sized so that the town block matched the same size as the blocks in the Saxe survey and then aligned with the same pond and canal in the Saxe survey (after overlaying the Saxe survey). The resize appears to be a good assumption because the symbol for the fort ends up having the exact same size in both surveys. Also, notice how the old Platt Springs Road lines up exactly with the road today. I believe this was the ferry road which lines up nicely with the recently located remains of the ferry ramp.
3. Another interesting point is that the pond shown in the northern portion of the Saxe survey matches the low lying area of the Riverland Park neighborhood.
4. I was not really trying to align the fort symbols of the Saxe Survey and the Granby map but, as you can see, they end up with the exact same position and size.
5. The river front quad of the fort is located on an undeveloped lot in the Riverland Park neighborhood.

The image below is large and you may need to use the scroll bars to view the full image. Click on the "faint overlay" link (below) to lower the opacity of the overlay.
Images of the Granby map and Saxe Gotha Town survey are also include below the following overlay.