Well, these might not look like much. But I needed 'em and the LS and J-tip found 'em. I also found a piece of buried barbed wire to the left of the nail in the top photo. This was the shake-down cruise with the J-tip out of the office. I left the Schonestedt in the truck and stuck the J-tip in my front shirt pocket. I didn't even know it was there. Nice not having to carry the Schonestedt around, especially as I was marking line and just checking into the nails to make sure all was good at each end of the line.
A couple of days ago I was surveying a small lot from a small subdivision done in 2011. I didn't know it when I started, but apparently the front of the lots were originally "ditch-to-drain". Sometime after the subdivision was developed, the ditch was filled in. Fortunately for me, when the fill was added, it did not disturb the front stakes, only covered them. The first one that I found was a 1/2" iron rod with ID cap, 16" deep. The second was a 1/2" iron rod with ID cap, 22" deep. I found both using the J-Tip.
I use the digital readout quite a bit to see the polarity and the strength of the signal. Unlike other detectors, the tones are used to alert the user to a magnetic signal and are scaled based on the current highest magnetic signal. This is to help with pinpointing an isolated signal. In areas of multiple signals, the tones are less useful and the digital readout on the LS becomes more significant. The digital scale "zeros" at an arbitrary value of 100. The sensors have a noise of about 1. So you might see 99 or 101 without changing the magnetic field surrounding the J-Tip. When the signal dips below 100, the polarity is negative. When the signal is above 100, the polarity is positive.
The 5PLS Team has done a lot of testing of the J-Tip with a lot of materials at various depths over the last several months. One thing I can share is experience that isn't just based on the J-Tip, but also on experience with other manufacturers as well. The magnetic field of two identical objects may not be aligned in the same way. I've seen 1/2" rebar give a strong signal and I've seen it give a very poor signal, or no signal at all. Sometimes, with a Schonstedt, I found rebar when the sound would go dead. There would be a slight hum around the rebar, but when I would be right over the rebar, the hum would go silent. For this reason, it's important for a surveyor to use a locator as a guide, but not the final authority on whether a stake is in the ground or not (a shovel still reigns supreme here). I grabbed 4 rebar from a bundle early in testing. Some were showing 200 or more while one was 4. The strength may indicate the size or depth of the object, but not always.
Back to the J-Tip, using our arbitrary scale, I've seen the values reach 200-700 when the J-Tip was on top of the rebar. The scale isn't linear. Close to 100 (neutral) any change is very big, but as the values change much from 100, the changes are less significant. A change in 200-300 isn't much change, where a change from 5 to 20 is very big. In the case of these two rebar, the 16" rebar showed a change of +4. The 22" rebar showed a change of +3. To the uninitiated, it might be that a signal like that would go unnoticed, but it is important for J-Tip users to become students of these values. You've likely never been presented with anything like it before. Small changes in values at the lower end of the scale represent big signals.
One more note. The scale for negative polarity is different from the scale for positive polarity. A -10 (which would be a 90) is much stronger than a +10 (which would be a 110). Sometimes a monument may have the negative end up, so you shouldn't dismiss all negative signals. Sometimes, when working along a fence, you may notice that the fence has a negative polarity, which makes it a little easier to ignore (but again, you can't always ignore it). The PLS team has also noticed that objects that are laying on their side in the search area can be identified by a strong positive signal with a strong negative signal a few inches away (or whatever length the object is). A screwdriver will give a positive signal at one end and a negative signal at the other. The two signals with be separated by the length of the screwdriver.
Oh wow, I just read that thread, I am not active on that forum. I just finished up a retracement survey where I found an older 1/2" bent iron pipe. Dug it out to where I could spin it and located it with the LS. But the pipe wasn't plumb after the bent section so I was hesitant to use this located position. I pulled the pipe and scanned again with the pin finder... still a signal there. Kept digging to find the bottom of the pipe, which was plumb. So the top had been bent and it had been snapped off 1.5' below grade. The horizontal distance between the undisturbed bottom and the spun location was about 0.20'. I considered setting a new monument at grade but I decided to leave the bottom of the pipe as is, with ribbon tied on and coming up to the surface. The broken top section was not put back in the hole. All of this will be noted on my survey plat, which will be recorded. I think this is the most important thing - to document what you did so that others can see as well. At another corner I found a very mangled 5/8" rebar right next to a newer fence post. I knew the post had been set after the existing pin due to landowner parol evidence, so I was hesitant to hold the location of this pin since it was most likely disturbed when they put the fence post in. The base of this pin wasn't plumb either, nevertheless, I located the disturbed position of this pin. After resolving the boundary, the disturbed location was within 0.10' of my calculated corner. Here I pulled the mangled pin and set a new rebar and cap. In my opinion, leaving a monument in a mangled state doesn't do anybody any favors, not the landowner, not the next Surveyor. This also will be fully noted on my plat.
Of course I got off topic a little as I do not have a JTip...not yet anyway!
Right on, Joe. That's the one bad thing about pipes. When they get old and bent they tend to twist off... somewhere. Good on you for digging until you got to the bottom of it (no pun intended). I also agree about mangled rods. I generally try to straighten them if I find them bent, but pipe is hard to repair as it tends to get brittle and some rods are so mangled that repairing them just isn't practical, so setting a new one in place and documenting this is the best choice.
In my example, this survey has zero chance of being recorded, so I set the 60d nails so that at least the next guy would have some notice that a corner is there (whether the next guy is the land owner or the next surveyors). I was barely able to detect these deep iron rods, I don't know if just anyone following me would have found them. Others mentioned setting pvc over the rods and cutting it at or near ground flush. That's a great idea that I may look to adopt in the future.
That's a little concerning -- an axle down a foot and a half usually gives off a good signal on a Schonstedt. Did you try another locator for comparison?
My understanding of magnetic locators is pretty shaky, but I'm under the impression that distance between the two sensors on a Schonstedt corresponds to sensitivity, which is the reason the extendable GA-92XTd isn't as sensitive as the clunky old GA-52Cx. Does the J-Tip use the LS mag sensor for comparison, or does it rely only on its internal sensor(s)? If the former, I'm wondering if the mag sensor in the LS isn't as effective as the purpose-built sensors on a Schonstedt.
There are two modes of operation for the J-Tip.
A: Single Sensor
B: Differential Sensors
Single sensor mode has no problem detecting a 5/8" iron bar at a depth of 3 feet. My old GA-52Cx could detect it also, but not nearly so obvious.
Differential Mode on the J-Tip has much less range, and is used when you are in a magnetically noisy area. It can differentiate a bar that is right next to a steel fence post.
You are correct that the distance between the sensors is important. Considering that the J-Tip is small...we had to get around that problem with sheer genius. Javad has said... "a magnetic sensor outputs signals...we are the best in the world at signal processing". That is the end of story regarding needing far sensor separation.
FWIW... I loaned my old Schoenstedt GA-52Cx to my good neighbor so he can clean fence post out of old fence rows of the farm. It would not really matter to me if he kept it. I prefer my J-Tip for its performance, and then there is that little issue of convenience
I found this one today a foot from a utility pole with several conduits running down it. Very noisy area. Notice the ground wire stapled to this side of the pole.
Following up on John's post, I used the differential and z axis to pin point the iron.