Assumed systems...and metadata

The thread below started by Kent reminded me of something that happened when I was a rookie surveyor.

A little background first...

I was hired by the USACE as a survey technician, no experience at all in surveying, but I did know something about maps (a self taught hobby when I was young). So, I worked on a USACE crew for a couple of years, and worked my way up to instrument man pretty quickly, and then party chief for summer crews. The district would hire 5 to 7 CE students from Pitt and Penn State to work in the summer, and they needed more party chiefs when that happened. Later, when I went back to school for CE (I was an EE student before that), I came in the summer as well each year until graduation.

One of the first jobs I had as a party chief was to do some topo of an area that was being flooded regularly so that they could design a flood wall. The office guy (chief of the survey branch) took a USGS quad, scaled a state plane coordinate for a street intersection, scaled a state plane coordinate for the next intersection to get an azimuth, and told me to set points in the center of the two intersections and use that data that he had given me. At the time it seemed reasonable, get it close to SPC. Now I realize the folly of that procedure. Probably no metadata at all accompanied the map that was created, other than to say it was NAD27 PA South Zone (which it wasn't). So, no one would know that it was the results of scaling (probably ±40' at best), and the elevation was also scaled from a 20 ft contour map.

It would have been better to do 10,000/10,000. Sometimes maybe no metadata is better than incorrect metadata.

I also knew of a photo control surveyor who would regularly do photo control the same way, he would use spot elevations off of USGS quad maps for elevation. He did this for years after GPS was available because he did not want to spend the money on equipment or run that extra few miles to tie in a benchmark. So the client gets something that LOOKS like SPC and NGVD29, but in reality was shifted significantly.

A final story about metadata...this happened on two MAJOR multi hundred million dollar public projects around here. A large engineering firm created modified state plane coordinate systems by applying a combined factor to the coordinates. This shifted the coordinates by about 100 feet in the Pittsburgh area. But of course that fact was left off of all the maps. Years later, people tried to bring in control from outside and would bust by 100 feet. They would then spend a lot of time checking their data, maybe even going out and re-running it.

So, to EMPHASIZE what Kent is trying to say...ACCURATE metadata is critical, especially now that we have multiple datums and realizations (with more to come).

In the past year I have done projects referenced to NAD27, NAD83 (86), NAD83 (2007), NAD83 (2011), WGS84 (G1150) epoch 2012.667, WGS84 (G1674) epoch 2013.921, and that's just the horizontal. For the vertical...NGVD 1929, NAVD 1988, EGM08, local datum...