This was written for a specific reason but there may be some areas of general interest in city surveying.
I like the 'pestilence of surveyors'
And you have some great photos there.
Page 11 figure 8 shows a calibrated wooden rod. What was the procedure used with these rods to measure the baseline?
That's a nice piece of work, Scott. You've always had my endorsement (surely not worth much) for fine geodetic work, but maybe one from CjatGPT is worth more:
ChatGPT said:
Yes, the coordinates Easting 2,008,942.41 and Northing 162,779.32 in the NAD27 New York Long Island State Plane Coordinate System (in feet) are a very reasonable approximation for the Prospect Water Tower's location. Here's why:
1. Comparison with the General Region:
- Brooklyn's NAD27 State Plane Coordinates for the Long Island Zone typically have Easting values around 2,000,000 feet and Northing values between 150,000–200,000 feet.
- The provided Easting (2,008,942.41) and Northing (162,779.32) fall comfortably within these ranges, making them a plausible approximation for a location near the center of Brooklyn, like Prospect Park.
2. Relation to the 1908 System:
- The 1908 Brooklyn Coordinate System places the Prospect Water Tower at (0, 0). When transitioning to NAD27 State Plane Coordinates, offsets are applied to match the Lambert Conformal Conic projection's grid.
- In the Long Island Zone, the False Easting of 300,000 feet (added to prevent negative Easting values) ensures that coordinates remain positive for the entire region.
3. Checking Against Geographic Coordinates:
Using the approximate geographic coordinates for the Prospect Water Tower in latitude/longitude (NAD27):
- Latitude: ~40.6643° N
- Longitude: ~-73.9688° W
When projected into the NAD27 State Plane (Long Island Zone), these geographic coordinates would indeed yield an Easting near 2,008,942 feet and a Northing near 162,779 feet.
4. Historical Survey Data:
- Historical survey data from the early 20th century for Prospect Park would align the water tower's location to match these State Plane Coordinates with high accuracy, as Prospect Park is one of the key points referenced in the Brooklyn system.
Conclusion:
Yes, the provided coordinates are a good approximation. However, if you're looking for greater precision (e.g., down to fractions of a foot), you might need to verify these numbers against detailed survey maps or use GIS software to project the exact latitude/longitude into the NAD27 system.
Would you like guidance on performing this verification or working with a specific GIS tool?
Again, great work!
My ++1 on the interesting history
May I ask why NAD27 and not something more recent? (dont you guys have a NAD83 or something)