Laser Rangefinder

[Bill93]

A year or two ago we discussed "laser" rangefinders, which at the time if affordable were mostly ultrasonic measurements with a laser pointer to help aim. Now it looks like there is a true laser distance measurement for $100 to $150.

Link to one of them

That is still a lot of bucks for a hobby, but if you can justify it for your work, it seems like it would make a great tool for checking the distance between reference marks and tri stations, or from other reference objects as well.

 

What I haven't seen discussed yet is how reflective the surface has to be to get that range.

 

Does anybody have experience?

[+Black Dog Trackers]

Looks very interesting.

I just saw one with free shipping on ebay for $109.

 

The round-the-corner pythagorean mode looks like fun although how do your make sure you have a right angle?

[+GEO*Trailblazer 1]

With prisms.

 

If I remember there are right angle.

 

There are also some on the Satts up there.

I will do some research.

Sattelite retroprism

 

You could use the EDM Baseline Measurment Stations in your area for calibration and see how far the reflectivity of the unit is.

400 meters to 1200 meters.

Edited November 18, 2008 by GEO*Trailblazer 1

[Wintertime]

A year or two ago we discussed "laser" rangefinders, which at the time if affordable were mostly ultrasonic measurements with a laser pointer to help aim. Now it looks like there is a true laser distance measurement for $100 to $150.

Hmmm, does that mean the Stanley FatMax I bought for $99 a couple of years ago is not a true laser measuring tool? I don't recall ever seeing a mention of ultrasonic technology in the manual. How can I tell whether it's really using the laser to measure?

 

What I haven't seen discussed yet is how reflective the surface has to be to get that range.

I generally bounce mine off of people.

 

Patty

[68-eldo]

Thanks for bringing this up this is a topic I was thinking of bringing it up.

 

I was looking at the laser(?) measuring tapes in Sears and noticed they were good for only about 50 feet. Then I noticed one that sold for over $200 that had a greater range (about 1000 ft. IIRC).

 

Then a guy showed me a pin from a golf course. It had corner reflectors on the top. Now I thought that the rangefinders for golfers was based on the height of the pin. But with corner reflectors that implies the golfers are using laser rangefinders. I don’t expect them to be very accurate but it would be interesting to look into.

[Bill93]

I think the Stanley TLM series is "true laser measurement." I didn't know they could be had at that low a price two years ago.

 

The way to test it is to measure the distance to two things at different distances and about the same angle, for instance the front of a counter and then the backsplash, or a door jamb and then the wall across the room. If it was ultrasonic, you wouldn't get nice distinct accurate readings.

 

The discussion I vaguely recall was for stuff in a lower bracket, maybe the $29.95 range.

[Wintertime]

Coincidentally, I just noticed that Habitat for Humanity Silicon Valley has two FatMax TLM100 units (same one I have) for sale for only $65 each. Details here:

 

http://www.doubleknot.com/openrosters/View...amp;orgkey=1651

 

I don't know whether they ship, but you could ask.

 

Patty

[+Black Dog Trackers]

The old topic is here.

 

Here's a description of the TLM 100 FatMax Tru-Laser distance measurer. Is that what you have, Patty? It's available at amazon.com, I see.

 

Trimble makes one too.

[+jwahl]

Leica Disto is I think a brand that is marketed to surveyors. Things you should look at besides range, are accuracy.

 

Also I am pretty sure, but not positive, that none of these gadgets will correct a slope measurement to a horizontal measurement, which is what most lines in surveys are reported in. So you would also need some kind of reasonably accurate clinometer and maybe an inexpensive scientific calculator to reduce the measured distance to horizontal..

 

There are a wide variety on ebay at any one given time. Reflective tape will probably help considerably and is a lot less expensive that a retro prism for hard shots.

 

- jlw

[+pgrig]

I have used both the Bosch and the Stanley TLM 300 in the field, and have found them to be a mixed bag.

 

Here is an example of the more expensive Stanley unit (about $400) at work. As I recall, it has about twice the range of the Bosch unit (say 75' as against 30'-40', unaided by a reflective tape target), and also has a simple internal sighting prism, which makes it much easier to point at a distance. My sample pix had it shooting at a white-painted porch pillar and a tree trunk.

 

I haven't used mine in a while, since I have been mostly out after ledge-emplaced marks, but I remember that I was having trouble with the Stanley being too sensitive when aimed at a reflective tape target. It would return an error code telling me that it had been "overwhelmed" by a too-strong reflection.

 

This is because I sometimes use a traffic cone with 3M-type reflective tape as a target and sometimes a cookie sheet that I have covered with reflective tape on one side. (I "nail" the cookie sheet to a tree or a telephone pole with an awl, or hang it from a hook on the cone. This provides a bigger target, needed at distances of about 75' or more too "catch" the laser beam.)

 

If it didn't freak out, I seem to remember that I could get accurate measurements in open shade (or at dusk) up to 125' or so. Bright sunshine often renders it ineffective, as do low-reflectance surfaces (e.g., dark tree trunks). It worked great off of rusty RR rails, however!

 

If folks are interested, I would be happy to run some additional tests and report the results here.

 

-Paul

[Bill93]

Most of the $100 category devices advertise a "typical accuracy" of +/- 1/16 inch. That's probably as good as a hardware store tape for 100 ft measurements, considering that you probably won't do temperature correction and don't know the sag constant.

 

Is the distance readout strictly limited by software regardless of target, or will a good target give you readings beyond the advertised range?

 

I found with my semi-antique surveyor's semi-total station (GTS-2B) that I could get distance readings from the red safety reflectors that look like a tail light. This machine doesn't like any of the few reflective tapes I tried. Some brands of safety reflector worked better than others. They are not perfect corner reflector arrays, but have a slightly skewed angle for dispersion to make them more visible when headlights and a driver are at different angles. The 3 inch ones were pretty good. The best ones (Hillman, sold by Home Depot) had about 8% of the range of a high quality 3 inch prism. The approx 1 inch diameter Cole safety reflectors didn't work as well as their relative size would predict. The near-end range was also limited because the reflections were not diffuse enough and sometimes the beam would hit the reflector and not come back at exactly the right angle.

[+pgrig]

Bill93--

 

I found that my reflective traffic cone target would extend the effective range of the tool a lot--like another 40-50%, if I remember correctly (subject to "overwhelming" the tool as mentioned above). I also found that the "spec'd" range of either the Bosch or the Stanley must have been measured indoors off of a white surface. No way could I get the "spec'd" distance measured outdoors in normal daylight (read partial sun) conditions, or with a target that was at all absorptive (as most "real" ones often are).

[timz2]

One big problem using a laser rangefinder outdoors is seeing the red laser dot-- at 100 ft it's fairly invisible unless you know just where to look, which you probably don't. Additional problem: holding it steady on the thing you're trying to measure to.

 

Those golf-course rangefinders are completely different-- they don't use a visible laser. You get a 6x view with a crosshair that you put on your target and it gives you the yardage, hopefully correct to a yard. It's surprising how often it can pick a flag out against the background, but it doesn't always succeed.

[+pgrig]

Thanks, timz2.

 

That's why the reflective tape target becomes important. It blazes like a lit flare when hit by the laser beam, even at distances of over 150 ft. (Stanley tool), but it takes a fairly big surface area (say 10x20 in.) so that you can hit the reflective target hand-held. [Of course you sometimes get the "overload problem".] And you're right--the dot dances around a lot hand-held at 150 ft. Still, I have learned to do it. The sight on the Stanley helps a lot to get you close. (The Bosch is much harder to use in this respect; you have to sight over a nib on the top edge of the tool and key a button that you then can't see...)