- NGS PID:
- N 40.271777° W 76.855072°
- 609.27 ft.
- Triangulation Station Disk
- Concrete Post
- Year Established:
- Established By:
- Not Found
- Unknown (Not Found) as of May 27, 2015
- Official Description: NGS Datasheet
Kristen and I were planning our trip to the CONTENTdm conference in Towson, Maryland. She suggested that I look for a few survey marks that we could search for along the way. What a great idea! (Of course, I had already planned to do just that.)
Our plans included a lunch stop along Union Deposit Road near Harrisburg, so I checked out the Harrisburg area on NGS's interactive map and found a tri-station, unsurprisingly named HARRISBURG, that appeared to be located in a park. Upon further research, though, I could see that something had changed drastically. Not only did it no longer appear to be a park, but satellite imagery showed a building right on top of the coordinates.
The building is the National Civil War Museum, and it was indeed built right on top of the tri-station's location in 1999/2000. We can only assume that the mark was destroyed during the construction. We were in desperate need of a leg stretch anyway by the time we arrived at the museum, so we wandered the grounds and can confirm that there is no sign of the station or either reference mark. The regrading and landscaping of the area between the museum building and the parking areas probably resulted in the destruction (or at least the burial) of both reference marks as well.
The strangest thing about this situation is that we found another mark, designated HARRISBURG RESET 1999, on the grounds. This disk is embedded in a set of concrete steps at the far eastern end of the field on the museum grounds. The year matches the year of museum construction, 1999, so setting a reset at that time would make sense—but this mark is a vertical control mark (a bench mark) while the original HARRISBURG is a triangulation station. We don't see how it could be a true reset/substitute for the original mark. Perhaps the vertical control was all that was needed in these days of GPS, so they took the cheaper route and set only a vertical control mark. In any case, the mark doesn't appear in the NGS database even though the disk is an NGS disk.
The original triangulation station and reference marks were not found. They are assumed destroyed by the construction of the National Civil War Museum and the associated regrading of the property. HARRISBURG RESET 1999 was recovered in accordance with the 2004 and 2008 recovery notes. It is set in the southeast end of the top step of a set of concrete steps at the eastern end of a field in Reservoir Park. The disk is a vertical control mark rather than a true reset of the original triangulation station. It does not appear to have its own entry in the NGS database. Handheld GPS coordinates for HARRISBURG RESET 1999 are 40 16 21.6(N) 076 51 12.0(W).