My wife bought me this package of five or so yellow laser devices. They throw lines that work okay if you are working in the dark, and the work doesn't have to be straight or plumb or level.
Then, there's one that measures distance. It doesn't work very well in the sunlight here in the desert southwest. But, I was playing with it today (a cloudy day here), and just wondered ..........
How accurate are they? It would be handy for some things I do, or are they just for guesstimating?
Steve
Most of the less expensive laser stuff is advertised as having an accuracy of 1mm per meter. Some of the cheaper stuff I have seen would be struggling to even reach that standard. What I do find useful, is using it as a substitute for a string line, or piano wire. The advantage of a light beam, is that it's dead nuts straight, and doesn't sag. Just remember to measure from the edge of the light, not the middle, for best results. Unless you can calibrate the bubbles, assume any spirit levels are only "moderately" aligned with the beam of light...
As for the distance measuring device, there should be some indictation somewhere how accurate it is.
These are mostly trash. I tried one out that someone gave me. It's just about useless. I do have a laser instrument that will read distances up to 3 mi. to
+/- 1 mm and reads angles, vertical & horizontal to 1 second of arc. It cost $25,000+ new. It is now obsolete, replaced by GPS. Bugs
I'm jealous. My GPS don't do dat. And I have need for sub-centimeter measurement over long distance. I presume from "obsolete" that you no longer use it?
Mike.
Sounds like high-end land surveying gear, probably made just as the military was first fielding GPS systems. IIRC Surveyors were the first to buy the equipment and mess around with GPS, and the first to get the military bypass keys around the "Selective Availability" encryption.
And they also invented "Differential GPS" - another receiver at a known fixed datum/bench point transmitting the exact 'fudge factor' needed to offset the SA accuracy degradation. But you'd still need to run the plots with the computerized laser transit to verify the figures and points.
Now that they've given up on SA, they probably allow the high- accuracy GPS systems to be the final arbiter - right?
-->--
According the Garmins website about GPS the first satellite was launched in
1978
They had gps in the late 60's. The one thing they didn't have was the miniature computers to spit out the computations. All the raw data was taken back to the lab and processed to fine the position information. It took about six minutes of data to get a reasonable position.
John
Before that it was Loran, but accuracy was nowhere near what GPS can do, and Loran's resolution is highly dependent on your location. I was working on boats around the time GPS was introduced and because of the limited number of satellites circa 1980 you could only count on getting a GPS fix something like 2-3 times per hour.
I had friends in offshore lobster fishing, and IIRC they were still relying primarily on Loran to locate their gear into at least the early 80s.
Ned Simmons
Newsgroups: rec.crafts.metalworking From: "Mike Young" - Find messages by this author Date: Sun, 25 Dec 2005 17:44:04 GMT Local: Sun, Dec 25 2005 12:44 pm Subject: Re: Laser measuring devices Reply | Reply to Author | Forward | Print | Individual Message | Show original | Report Abuse
I'm jealous. My GPS don't do dat. And I have need for sub-centimeter measurement over long distance. I presume from "obsolete" that you no longer use it?
I still get it out once in a while to do some work around the house. Can't really justify keeping it. It also has a fairly primitive data collector. It's a Nikon 1 sec. laser theodolite. Bugs
There were a couple of navigation satellite systems before GPS. One required visual sighting of a satellite, and tables of the ephemeris- a real pain to use. I believe it was based on triangulation rather than the GPS tri-lateration. Wish I could remember the name of it.
GPS was a second generation navsat.
For high precision GPS you need differential GPS. If in the sticks, you may need to create your own pseudo-satellite, but near populated areas and major airports, you may be able to use someone else's. I see many of the consumer GPS systems now say they are capable of differential GPS.
Also, even with differential, to get sub-cm precision you need to sit receiver there for a lengthy time, averaging the readings.
Transit? Actually, one used the doppler signal from the satellite as it flew by, in low orbit. It did have to be visible, which was not always true, but once in view the receiver did the work.
Joe Gwinn
If you cant find the room for it..Im sure Id put it to good use, when accompanied by a 300 Winchester Magnum. My little double image range finder isnt accurate enough out past 600 meters.
And I have some friends with .50 Barretts.....
Gunner
"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.
Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner
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