HARRISBURG

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.