David,
I understand you are tired of me, as I am of you. Even that withstanding, I just have to call BS on your last post.
In this case, my “definite pronouncements” are based on my experience. I think I can know about that survey with a real degree of definiteness – no self-proclaimed and self-hyped 'expertise' necessary. If you want to harp on “window to time travel” take it up with Patrick, who acts as if he knows what folks saw from a train on a winter day.
If we want to fill in any casual readers who might not know better, it’s to tell them that in this case you are the one really full of bull. But people can believe someone who has done and used the mapping or someone who looked up the definition in a book.
At this point, I type this out for the few on this site who still want to learn something. I am not interested in your specific argument about the photo not being taken from the 6th fairway, because the lowest tech instrument available – my own eyes – tell me the features fit. How you can be analyzing distant hills to try to make a case, I just don’t have a clue.
I have no doubt that you have a rudimentary understanding of the science and geometry underlying surveying, but you got it from a book. Perhaps as I have a rudimentary idea of what a lawyer does because I have been sued, been a witness, etc. I even got a chance to play lawyer years ago in a public hearing regarding a superintendent.
With all due respect, and I have as mentioned, I have done site surveys, worked with them and understand their methods. I still keep an old transit at home “just in case” I need to go shoot a few grades. Much of this post is written just for the fun of reviewing stuff I did more of in the old days (circa 1973-1990 or so)
And having used both site topo surveys and USGS aerial quad maps for the same purpose as Crump and on the same project, I know which is more accurate.
I didn’t mention it, but I took an aerial survey class in college and actually produced a USGS type map using the same stereoscope aerial photos. If you saw that method, where you trace over “stereo” (slightly off set aerial photos) and you try to trace along a line that makes the stereoscope appear to remain on the ground, but if you go too low it looks as if it’s digging a hole or too high and it jumps off the page at you, you would realize it just isn’t as accurate as hand surveying, and really depends on the diligence of the user. And, those topo maps are made from relatively few known ground elevations.
Also, there is distortion in varying rates in any aerial photo. It varies with if the plane was truly vertical (Not always possible in high winds, but made easier with the advent of gyroscopes which stay steady)
The methods are such that the computer and photographically generated topos have much more chance of garbage in, garbage out than a survey instrument. (That phrase wasn’t even invented until computers came around!) Surveyors are trained by nature to be accurate. Aerial photo mapping can sure cover more ground, but its at the expense of detailed accuracy.
BTW, there are different levels of hand surveying. While Golf Course Architects prefer aerial topos because they are good enough for our use, housing developers nearly always prefer the hand surveyed topos to this day, because they give them the accuracy they need.
Of course, for those of you trying to re-write history to make names for yourselves are prone to believe that every darn thing done by some old guy is wrong…but in the case of surveyors, I know that 99.99% accuracy rate is probably very accurate to how they work.
As to your specific questions about what the reference elevations were, they all relate to sea level. One of the early tasks of the USGS was to establish true benchmarks related to sea level at regular intervals so other surveyors could do their work with confidence. There are numerous elevation markers around the country, generally at intervals so a surveyor doesn’t have to go very far (a few miles) to tie into the national coordinate system. If the benchmark is not visible, then they have to traverse to it, perhaps using many set ups of the instrument in locations that eventually get that benchmark back to their site.
Is it possible they failed? I know of no known instance of a USGS bench monument to be wrong. I know of only a miniscule percentage of qualified surveyors who would make such a mistake. Properly done, there is absolutely no doubt that a fine scale, hand surveyed map is more accurate than an aerially obtained USGS Map. None.
“Holding a stick” as you call it is actually very precise. It has markings to either 0.1 or 0.01 feet. Looking through the transit or level it is very easy to read at distances up to 600 feet or so. (Optics probably got better over the years, but they could surely see 300 or more feet even in 1913) If you know the level of your instrument from the benchmark, something like 184.55, then you read the stick and if it reads, say 12.22, then you subtract that and the pole is sitting at an elevation of 172.33. Voila. Taken from right on the ground, not 1000 feet in the air. Which do you think is more accurate?
Besides that, the method of surveying a grid has built in checks and balances. If I survey four grid points and they are on reasonably flat ground, but they register as elevations 180.23, 181.45, 184.56 and 122.00, do you think a conscientious surveyor would notice his one data point mistake and do it over? How would a pilot know if he was askew a bit, and how qualified/motivate is the guy running the stereoscope but never having seen the actual ground going to know if there is a mistake?
Mostly, the purpose of the USGS maps must be considered as general, and not construction specific, and they were never intended to be accurate. But if you want to hold out hope that Crump’s surveyor was one of the 0.0001% of mistaken surveys by a registered surveyor, and mistaken to the degree that their elevations were consistently off by more than the minimum accuracy of the USGS maps, then go ahead.
Unless proven otherwise by another on site survey, it is not at all unreasonable or ironic to put faith in a site survey. Builders, property buyers, courts, etc. have done it for centuries, but only on golf club atlas would someone question all that went before in favor of deciding after a few moments of thought that it was very likely that everyone else gets it wrong until we come along to prove that very fact.
LOL
BTW, I will admit that after careful review, your work on the 10th at Merion was pretty accurate. I believe I said that when I came to your way of thinking, at that time.
That is why, while I am convinced that your search for an alternate location of this photo is a bit of a herring, I wouldn’t ever discourage it. It’s not that commonly held assumptions are never wrong, but in the last few years, IMHO, just far too many of our arguments are based on such presumptions. You aren’t always wrong either, but I do believe you are wrong on your assessment of this photo, and the lengths to which you are going to attempt to prove it.
As always, just MHO.
Cheers to all.