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| Historical Question for the Strasburg Folks https://www.rypn.org/forums/viewtopic.php?f=1&t=24517 |
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| Author: | Christian S. [ Tue Dec 25, 2007 5:01 pm ] |
| Post subject: | Historical Question for the Strasburg Folks |
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| Author: | bbunge [ Tue Dec 25, 2007 7:39 pm ] |
| Post subject: | Re: Historical Question for the Strasburg Folks |
Quote: I discovered a handy little feature in Google Earth that allows you to measure the exact distance between two points on the topographical map with a simple click of the browser.
I would not trust the accuracy of this service to any less than a kilometer or worse, with amount of uncertainty varying by location. The large number of different data sources GE uses presents some difficult geospatial challenges. Where I work, we've documented a good amount of uncertainty in GE positions. This is perhaps related to how the different base geodata data sets used are related back to the various "datums" that describe the shape of the Earth. If you want to sort of see this in action, take a GPS unit outside, dig down into the menu system to find where you select different datums. Without moving the unit, select a datum, let the unit sit for 15 minutes and record the lat/lon. Repeat for each datum offered in the unit. Now plot the lat/lons on GE and use the tool mentioned above to measure the distance between the plotted points. Bob Bunge |
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| Author: | dr dodge [ Thu Dec 27, 2007 1:08 am ] |
| Post subject: | Re: Historical Question for the Strasburg Folks |
I am pretty sure that the accuracy of the readings is also gov controlled. It has to do with satelite sync's among other things (I believe I read something about it being lower uncertainty (25 meters) before the war on terror) Has to do with the ability to hit a specific target using GPS coords from an air attack Thats why GPS is not completely relyed on for air travel (even though it could be) also makes you think if they actually could find you in a city using your cell phone GPS (even though they do it on TV) another interesting observation at the beginning of this year, we were using google for business travel maps from Houston TX to Sarasota FL there was about 140 mile error come to find out, they were counting cities at the city limits, and not taking into account the distance across. Its fixed now (and cell phone time can vary by 1-8 minutes, on 2 phones, same provider service plan, side by side (and one actually was eastern time and the other central time for almost 100 miles) dr |
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| Author: | Warren [ Thu Dec 27, 2007 12:23 pm ] |
| Post subject: | Re: Historical Question for the Strasburg Folks |
I have the complete opposite experiance with GPS and I use it on a regular basis on our boat in the Atlantic Ocean and Delaware Bay. It used to be fairly inaccurate before the 'select availablity' signal scrambler was turned of by the government. When the select avilability was turned on, my GPS would show our boat moving while it was sitting in the drivewayup to 35 meters in any direction. Without it, the accuracy tightened up to about 10 meters. With the advent of WAAS it's well within the 2 meter range. I can run a set of waypoints on a route for bouys through an inlet and be right on the mark everytime, as long as the bouys haven't moved of course. I'm not saying there can't be any inaccuracies, that just I've never seen anything lately. Interesting,hmmmmm. |
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| Author: | Christian S. [ Thu Dec 27, 2007 8:31 pm ] |
| Post subject: | Re: Historical Question for the Strasburg Folks |
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| Author: | Bobharbison [ Fri Dec 28, 2007 12:46 pm ] |
| Post subject: | Re: Historical Question for the Strasburg Folks |
Christian said: Christian S. wrote: Greetings, folks:
Recently I discovered a handy little feature in Google Earth... and then most of the replies went off on a debate regarding the accuracy of GPS systems. The two are totally different systems. Google earth's measurements are fairly accurate but they can vary somewhat. I've used them for some site development work, and consider them to be "order of magnitude" type info, rather than truly accurate. If you measure a siding to be 1,000 feet in Google earth, you know that's roughly what it will be, but I wouldn't be surprised to find it to be 900 feet or 1100 feet. Still, the discrepency you mention does seem to a bit more than I'd expect. |
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| Author: | Gavin Hamilton [ Fri Dec 28, 2007 3:18 pm ] |
| Post subject: | Re: Historical Question for the Strasburg Folks |
Also don't forget that you attempting to measure something that exists in three dimensions as if it was flat.... |
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| Author: | Howard P. [ Fri Dec 28, 2007 9:38 pm ] |
| Post subject: | Re: Historical Question for the Strasburg Folks |
Speaking of "historical questions" for the SRC people, have any pre-1958 photos surfaced? I recall the first ("full-color") small-sized edition of the SRC Story, and there was only the photo of the right of way when the 1958 owners took over. Any shots from the 30-50s? Another image in that book was the shot of the PRR Harrisburg block truck and foreman, after coming over the SRC's shop to change a wheelset on 31's tender. My, how different things would be 10 years later, when the GG1s were limped into that yard for patching up!!! |
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| Author: | K.R. Bell [ Sun Dec 30, 2007 6:38 pm ] |
| Post subject: | Re: Historical Question for the Strasburg Folks |
The 4-1/2 miles actually originated with the early 1830s survey of the railroad from the Swan Hotel on the west side of Strasburg. The railroad has always stuck by this figure despite conflicting evidence that tracks were laid down Main Street as a horse drawn railroad. I think the three and a half miles may be correct - I once tried calculating the mileage using the odometer on the Reading buisness car and it seems to collaborate your figures more or less. Howard P. asked about pre-1958 images of the railroad--there are several that exist. I have been writing a comprehensive history of the Strasburg RR for the past 15 years and have collected several early images (scans and prints), though not many exist. When the book is completed you'll see most of them, plus many heretofore unpublished views of the railroad from 1958 to the present. It will be **everything** you ever wanted to know about the Strasburg RR from a historical perspective. The book will also correct many errors that have been repeated over the years in various published sources. I'm not sure when the book will be completed, but my best guess is 2-3 years. I have the research almost all done; now the fun part begins. Stay tuned. K.R. Bell Strasburg, Pa. |
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