For discussing electronic tools.

12 responses total.

What does a Digital Protractor do, and how? The specs on a Accupro-Gold D.P.
are
   Range:          360 d (90 d x 4)
   Resolution:     +/- 0.1 d
   Accuracy:       +/- 0.1 d, level +/- 10 d
   Plumb:          +/- 10 d, +/- 0.2 d max. error
   Repeatability:  +/- 0.1 d

have any one experience sunraysthin client technology
hp new series with sleek processorunit

I had never head of a digital protractor before.  There are a couple of
basic types:  One has two legs, hinged at one end, that can be set at any
angle.  The angle between the two legs is displayed on a little readout.  The
other is, more or less, a torpedo level that indicates the angle it's at. 
Some will do both and some have lasers so that the angle can be project.

Both systems depend on a slotted wheel to figure out the angle.  In one case
the slotted wheel is referenced to the two legs, in the other case, it is
referenced to the device and a mass that is allowed to swing.  At least that's
the way I think they work ;-)

The picture (in a MSC catalog) looks like a chunky level. It has a LCD in
degrees, and on/off switch, a "hold" button, and a "alt zero" button.
No laser. This certainly sounds like "other". Perhaps the "alt zero"
zeroes it at a initial angle and then reads the difference from that? The
specs seem to imply that it is most accurate when level or plumb (+/- 10 d),
but will measure 360 d. 

I want to do a detailed contour map of several acres with a resolution of
one foot or so, and am looking for ways to conveniently and rapidly set
the level grid. I guess I need one of these with a laser. 

Yes, I would suspect that alt zero does exactly as you suggest.  You could
also use a transit.  Basicly just a telescope with cross hairs.  Set it up
level on a high spot and have a second person walk around with a long ruler.
Sight the ruler and take a reading and then move it to your next grid point.
I've never surveyed anything but I suspect I'm close.  Modern surveyors
seem to be one-man operations.  The transit reads the measurement and
records it along with the location of the digital ruler being measured
(Via corrected GPS)  The data is then dumped into a 3-D program that
models the measured terrain on a computer screen.

I have surveyed caves, but not with a transit - you can't *fit* a transit
into some caves I have surveyed. What I don't know is how accurately one
can level a transit: that+/- 0.1 d of the digital protractor is still +/-
17 cm at 100 meters. I'll look into it - though if a manual transit will
do it - it will have to continue in a different item. 8^}

Really modern transits record not only azimuth and elevation, but measure
the distance based on the return time of a light pulse - don't think I can
afford one of those. 

Here's a cheap idea:  Take a turntable of some sort, along with a loser
pointer, a level, and a long measuring stick.  Find the high point and put
the turntable there.  Level it very carefull, then attach the laser pointer.
Then walk around seeing where the beam hits the measuring stick.  

OK, you'ad probably have to do it at night, and it would be tricky to make
the laser pointer nice and level.

A cheap laser pointer spreads quite a bit - more than that 17 cm at 100
meters. 

In caves I have used the water-filled tube system for leveling, and it
can of course be used outdoors for setting up stakes on a very large grid,
and then using them to reduce the grid. So, what is the electronic version
of that? (I'm looking for ways to reduce labor - which electronics are
allegedly good for - yes?)

I just borrowed a cheap laser transit from the builder next door to identify
our property line from two survey stakes.  The distance was about 100 meters
but the spread of the laser beam was only about 6 cm.  It was pretty easy to
guess the center of the beam at the far end.  We did, however, have to do it
at dusk and dealing with the mosquitoes was no fun!  Vegetation also gets in
the way of any optical means.

I wonder if one could rent one of those fancy transits?

Scott, I was just thinking of doing what you suggested.  I'm in the process
of  building a pole barn and I thought that scheme would be great for drawing
a flat, level line for cutting posts and nailing boards around the
circumference so they would be horizontal and their ends would meet when I
complete the circle.

The water tube would be excellent for that, Klaus. Accurate to a mm or two.

There is a laser device that floats in a tub of water used by construction
people.

As for accuracy, the British survey team got the height of Mt. Everest to
within 24 feet of modern estimates, as I remember.  That was over one hundred
years ago.  With redundant measurements and trig, you can correct for errors.

I have a commercial water level that I got at the hardware store.  It has a
little sensor that beeps so that one person can use it.  Over time, grunge
grew in the water tube and effected its accuracy.  If I over filled the tube
and held the tubes such that one meniscus was right next to the other, the
one would be about 3 mm higher than the other!  Perpetual motion machine,
thought I!  (Till I figure out it was the grunge on the wall of the tubing
effecting things.)

I used it a lot while building my house.  It's slow to use and the range is
limited to the length of the tube.  When it was cold outside, the tube became
stiff.  When it was hot outside, the tube was so limp that it took quite a
while the water in it to settle down.  Even the slightest movement of the
water filled tube would upset the water in it.  A rotating laser level would
have been much faster.  Yeah, I'll use the water level for the pole barn.

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