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New Casio fx-FD10 Chinese Pro
03-30-2014, 05:44 AM
Post: #11
RE: New Casio fx-FD10 Chinese Pro
It's official, there you go:

(03-28-2014 03:31 AM)Den Belillo (Martinez Ca.) Wrote:  Manolo;

The only spirals I'm familiar with are Barnet spirals, used in railroads and some highways. Maybe these are a sub-class of your Cornu spirals? Barnets were chosen because the guys in the field in the 1800's could calculate the layout for construction without needing transcendental functions. Many things needed trig tables, but points on center line could be done with an algebraic formula and the degree of curvature. That's a plus when Indians are slinging arrows at you and bears are biting your behind.
A lot of surveying is retracement, AKA: "yes; what he said". A strange result of this is that as the land got subdivided, lots of deeds got written with calls like ".....along said line which is 40 feet easterly of the centerline of the ATSF RR...." or other nonsense like that. The result is that some of property boundaries have spiral curves in them even if the railroad is long gone. Today's surveyor has to "retrace the footsteps of the original surveyor", so he uses the same formula, which was as you know, chosen to eliminate wear and squeaking wheels.

I didn't catch the backlit screen. I don't read Congi so i was cheating by skimming the comments and replies. I guess i missed one. Night surveying - and the need to shoot Polaris, or to do very long triangulation with lighted sites to eliminate daytime heat waves - went out when GPS came in. A lot of art has died in the last 20 years.

Un-equal tangent vertical curves are only used in cases with real funkey existing conditions. Let's say you need to align a freeway offramp over a live 9ft sewer pipe but staying under an overpass, all while making a smooth transition and not leaving the driver's stomach in his throat or under his seat. I never had to do that but I have a program for the 11C for it. Aren't HP calculators wonderful? - db

Yes, they are indeed.

Den, that is fascinating. I've never thought of the effects of temperature, but it makes a lot of sense because light in an stratified medium (as density changes with temperature, hence index of refraction) doesn't follow straight paths, very nice.

In Spain, the current (2000) standard specifications for construction of roads only allow clothoids as the transition curves. That is Euler spirals - Cornu spirals... Maybe those are the same as the railroad transition spirals. I've noticed that there is an often quoted (U.S. Government Printing Office) 1938 book from Barnett that describes such spirals for highways, I haven't seen it yet.

Then there is the "railroad taper" too and so many others... It gets very interesting from here (but alas, it'll have to wait). Thank you!
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Messages In This Thread
New Casio fx-FD10 Chinese Pro - CR Haeger - 03-27-2014, 07:13 PM
RE: New Casio fx-FD10 Chinese Pro - hp41cx - 03-27-2014, 07:29 PM
RE: New Casio fx-FD10 Chinese Pro - colinh - 03-27-2014, 08:49 PM
RE: New Casio fx-FD10 Chinese Pro - d b - 03-28-2014, 12:04 AM
RE: New Casio fx-FD10 Chinese Pro - d b - 03-28-2014, 03:31 AM
RE: New Casio fx-FD10 Chinese Pro - Manolo Sobrino - 03-30-2014 05:44 AM
RE: New Casio fx-FD10 Chinese Pro - jebem - 03-30-2014, 03:46 PM

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