How reliable is the mini prism? I've always avoided using one as I have just always used a 1.5' rod for detail work. I don't feel confident that I could hold a mini level, it just looks uncomfortable at best.
> How reliable is the mini prism? I've always avoided using one as I have just always used a 1.5' rod for detail work. I don't feel confident that I could hold a mini level, it just looks uncomfortable at best.
Works pretty good for me.
Although I have now gone to one of these setups.
What I find is that a lot of people choose to measure short distances with these on concrete. I've always found that if you can properly pull a tape you'll always be more accurate.
Ralph
sorry to be confusing (lack of sleep...)
i mean just a prism with a point on the bottom.
i like the setup you have ralph. i've used a similar rod and just use the hammer as a prop for just about always.
They have worked out well for me but I prefer a mini on the bracket used to mount on string, which I have not qualms about doing. If you can see down that far I do not really see the point of adding a level bubble to the mix. A sticky target on a site card works well also.
I have three different types.
2 0mm and 30mm offset with no bubble adjustments
1 0mm fixed offset with bubble adjustments
I do not trust any of my mini prism bubbles on top of a 4ft pole
At 0.2+ ft HI it is acceptable and as good as any other prism setup.
0.02
> How reliable is the mini prism? I've always avoided using one as I have just always used a 1.5' rod for detail work. I don't feel confident that I could hold a mini level, it just looks uncomfortable at best.
I recently began using a mini-tripod to brace my hand (see the [msg=194895]Mini Tripod thread[/msg]), and I've been getting excellent results using it with the Leica mini-prism and a Leica TCRA1102 robot. I think the Leica prism has an 8' bubble; it seems to be very sensitive.
The typical situation I've been dealing with involves tying out an existing land net monument in a rural road intersection. I set a control point in each of two quadrants of the intersection, and a backsight point a couple of hundred feet away that's visible from both control points. I set up on one control point, tie the backsight, the other control point, and the monument, then set points in the other two quadrants on the calculated line between each control point and the monument. Then I set up on the other control point and tie the backsight and all 4 other points. (See diagram below).
I check the double-tied points in the data collector while in field, and rarely miss by more than 0.004', with most of the checks coming in around 0.002' or 0.003'. Back in the office I load everything into Star*Net and adjust. The resulting standard errors within each site are typically less than 0.01', with 95% errors in the 0.015' to 0.020' range. Sometimes (I've gotten kind of complacent) I'll use the gun to visually check the alignment from control point to monument to online point, and have always landed on the nail head, often right on the punch mark.
It's overkill for what I'm doing, but I'm having fun.
> sorry to be confusing (lack of sleep...)
>
> i mean just a prism with a point on the bottom.
>
>
>
> i like the setup you have ralph. i've used a similar rod and just use the hammer as a prop for just about always.
Sorry Spledeus,
Here's a picture of mine (mounted on a column bracket)
I find they work pretty well, mine is .32' high. The main issue I've had with the type you show (I have 2 of them) is that the housing tends to get out of whack if it's bumped around too much.
Ralph
I have used them for years and keep one on my belt most of the time. I like the plumb bob bracket that came with it also. I carry the 1 foot prism pole in my hammer holder on my bibs.
> What I find is that a lot of people choose to measure short distances with these on concrete. I've always found that if you can properly pull a tape you'll always be more accurate.
Using a tape for distance less than 20 or so has proven to be more accurate in my experience when preforming layout. If you don't have the prism tilted exactly at the gun it adds a little error. Also, even the latest and greatest guns still lose a little accuracy while plunging the barrel. My 0.04'
I'm using that exact same SECO mini with the robot. I have smart target settings for a 2m fixed rod with 360 prism and one for the mini. I use the fixed 2m to track the robot to the structure I want to shoot. The I crown royal bag the 360 prism and "steal" the robot with the mini and then reverse. Works pretty good.
What range can you get with these mini-prisms and a modern gun? Must be far more than you need for most layout work?
Why aren't micro-prisms common, say a couple millimeters diameter? Something so small, still having a range of hundreds of meters, could sit so close to the point that leveling would be trivial, without several tenths or more of height.
> What range can you get with these mini-prisms and a modern gun?
The Leica 1100 -- which can't really be called a "modern gun" anymore -- is spec'd at 2,000 meters to a mini-prism under ideal conditions, 800 meters with severe heat shimmer.
I've never seen a micro-prism, but it's an interesting idea.
If I can see right down on a point the preferred option is a retro-reflective target mounted vertically on something. I have few stuck on different little pressed metal L pieces I have found around site. The 8m tape measure is a favourite as it is always in your pocket and you're unlikely to forget to pick it up as you will be looking for it quite quickly if you do leave it.
These do require a non prism (DR) measurement once you are further than about 20m away.
Micro prisms are a real "thinking out of the box" idea but they would have to be cheap enough to sprinkle round the place like fairy dust! I can't see them being practical to pick up and put down. Maybe if they are mounted in something?
my pic was some stock picture, but our mini is similar
i have just always felt there is more reliability with the prism on a short rod
so i have avoided the mini all by itself
just seems uncomfortable unless you have one of those fancy tripods jim made... perhaps if he added a little cushion i'd be convinced.
> my pic was some stock picture, but our mini is similar
>
> i have just always felt there is more reliability with the prism on a short rod
> so i have avoided the mini all by itself
> just seems uncomfortable unless you have one of those fancy tripods jim made... perhaps if he added a little cushion i'd be convinced.
I thought about you today and gave this a shot
