Some Helpful Engineers Notes for Viewers: (1) The two peg test here is correct but the 1 mm error in 16 meters is really is about hidden in the noise of the readings. The rod reads to 5mm and you can read it easy to 1mm since the Auto level is typically 24 X in power. You have two rod readings at 8 meters, one at 16 meters and one at a few meters. If you Root Mean Square/RMS the errors you probably have 1 to 2 mm total. So the instrument is like really off 1 mm +/- 1.5mm in 16 meters. So an instrument that is "off" say 10 to 20 mm in 16 meters make a better example! (2) An auto level like that is typically 24X. They do make 20, 22, 24, 26, 30 ,32 etc but 24 to 26X instruments are most common. (3) In the USA a typical box store 24X Auto level is usually aligned to about 1/8 inch in 100 ft when built in China. 3.18mm in 100ft . That is one part in 9600 parts. ie 1 mm in 9.60 meters. All the shipping and bumps sometimes makes a low end instrument be like 1/4 inch error in 100 ft, ie 6.35 mm in 100ft. That is one part in 4800 parts. ie 1 mm error in 4.80 meters, (4) If Joe Good contractor takes care of the level the instrument will stay aligned for years and decades. Think cellphones, cameras, etc they often get dropped too. (5) If John Rough Contractor throws the level around like a shovel in his pickup after awhile the compensator hanging tapes in the auto level will stretch or even break. Then you have a real error of say 0.1 or 0.2 ft in 100 ft . ( 10 mm or 20 mm in 10 meters). If he drops the instrument hard you might get an gross huge error of 1 to 2 ft in 100 ft. (100 to 200mm in 10 meters) (6) With a BIG bump the instrument's compensator will no long hang down correctly and the instrument cannot be aligned unless the compensator is replaced or restrung. It is like if a 50 stone man sits on the children's swing set and the chains break or something gets stretched and the swing does not hang properly. (7) Most auto levels get out of alignment by being abused. ie dropped or bumped hard. Lending one out is risky , folks often do not care. (8) Auto levels used around concrete work often get concrete dust all over them. Sometimes the compensator gets stuck. Tilt the instrument slightly with a leveling screw towards you object to make sure the line of sight still is true. The "compensator" is the prism or mirror suspended inside that makes the level "shoot level" . It does this over a narrow range, when the bullseye vial bubble is sort of aligned. Many instruments will read true once the compensator is not stuck, ie you tap the instrument lightly. (9) You can check you instrument by moving it and taking the same readings again. Lets say a buildings slab to be poured is is 10 meters by 20 meters. Put the instrument in the center and measure the 4 corners heights to the corner boards. Let say they all are 1.50 meters . They all are the same distance from the level so any collimation/ slope error of the level does not matter. Then move the instrument close to one corner, the same distance to the next two, and farthest for the last one. You might get 1.498, 1.500 1,500 and 1.502. Or you might get 1.45, 1.50, 1.55 meters if your instruments is way off.
Its easy to calibrate level yourself.. do not trust a calibration shop.. I did it once and they screwed it up bad. The way to calibrate is pick two points 50 to 100 feet apart. Set the level within ten feet of one point-- shoot to the far point-- and then spin 180 to the close point-- measure the difference-- Than move the level to the far point in the same manner.. the differences should be the same.. To adjust-- turn the calibration screws one half the difference and check again.. Keep doing it until you get it so there is no error . I was a carpenter for 35 years. Never tighten down the levels adjustments to tight or you will bend or warp the table. Do not trust laser levels either until you check in the same manner.. Yes i have used bad lasers and level/transits. Also when you set up a level spin in 180 and 90 degrees to make sure it is level in all directions. Never assume any level tool is calibrated.. IT WILL COST YOU IF YOU DO SOONER OR LATTER.
I was wonder why he added the two backside readings and then the foreside. Why did he add instead of subtracting the first two readings and then the second two and subtracting the results? But the arithmetic comes out the same. Abs-Bfs-[Bbs-Afs] is what I would have intuitively done, but that comes out to Abs-Bfs-Bbs+Afs=Abs+Afs-[Bfs+Bbs] same as he did. The answer for me was solved by realizing that his 1st reading he calls a backsight this is toward the camera and at A, the second reading to point B he is calling a foresight (away from the camera). After he moves the tripod and takes a reading towards the camera at B which he called a backsight. The same direction now toward the camera and toward A is now called a Foresight (which I don't get why). Either way, if you subtract the first two reading A bs=1.148 and B fs=1.268 you get the true difference in height=0.120mm=absolute value|1.148-1.268|. If there is an error in level it would be some angle theta Up towards A say, but opposite down toward B or vice versa. If the distance from the tripod to A is the same as the distance to B, call it D, then the magnitude of the error would be D(tan(theta)). But one up, the other down so they cancel each other out. So you have the true difference in height 0.120mm. He moves the tripod and measures the height relative the tripod again. This time both in the same direction, toward the camera. Now the errors don't cancel. He gets a difference now of 0.119mm=absolute value|1.284-1.165|. That is different from the true difference by 0.001mm=0.120-0.119mm. I don't know where the 16meters comes from that he uses for the average error over 16m but I suspect it's the distance from the second position of the tripod to A. Wish that was shown, however.
that 1 mm error is not coming from the instrument itself but from the readings taken. reading a 1.148 on a leveling rod means that third digit is just an approximation of the surveyor.. you should send your engineer's automatic level to a calibrating shop.
That calculation was very confusing, it wasn't explained what backsight and foresight are. Why can't you just say that the height differences measured from the two locations should be the same and if they aren't then the amount by which they differ is the error.
I do realize that the metric system is superior, I suppose, however, that rod is confusing as heck to me. I'm going to go to my grave reading feet, tenths, and hundredths and do just fine.
you first recorded the point A on backsight and then point B on backsight when the station was moved beyond point B from the centre, and how is that waving the staff helpful for getting correct reading?
as u have moved the level to other position now doing this will change the height of instrument and this will affect the new levels?? taking levels from two different locations and adding them up? how can this be compared?/
Adedeji Oludayo what's important is the pegs don't move. Pound them in so they don't move. Same as the steaks. If the ground is hard, use a tool, frost pin or cribbing pin to make a hole in the ground first to get your steak in. If you're Stakes blow over in the wind after you leave the site, you haven't done your job well and the people on that site won't want to have your Surveying Company back.
At 5:06 you say "2mm over 16m is quite acceptable", yet at 4:50 you said "0.001mm over 16m". Really? You didn't pick up these confusing mistakes in editing? Unless I'm wrong, isn't it an error of 1mm (or 0.001m, not 0.001mm) over 16m? With an error of 2mm over 30m? Also, could you please fix up the play list order? No wonder students, including myself, are confused.
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Some Helpful Engineers Notes for Viewers:
(1) The two peg test here is correct but the 1 mm error in 16 meters is really is about hidden in the noise of the readings. The rod reads to 5mm and you can read it easy to 1mm since the Auto level is typically 24 X in power. You have two rod readings at 8 meters, one at 16 meters and one at a few meters. If you Root Mean Square/RMS the errors you probably have 1 to 2 mm total. So the instrument is like really off 1 mm +/- 1.5mm in 16 meters.
So an instrument that is "off" say 10 to 20 mm in 16 meters make a better example!
(2) An auto level like that is typically 24X. They do make 20, 22, 24, 26, 30 ,32 etc but 24 to 26X instruments are most common.
(3) In the USA a typical box store 24X Auto level is usually aligned to about 1/8 inch in 100 ft when built in China. 3.18mm in 100ft . That is one part in 9600 parts. ie 1 mm in 9.60 meters. All the shipping and bumps sometimes makes a low end instrument be like 1/4 inch error in 100 ft, ie 6.35 mm in 100ft. That is one part in 4800 parts. ie 1 mm error in 4.80 meters,
(4) If Joe Good contractor takes care of the level the instrument will stay aligned for years and decades. Think cellphones, cameras, etc they often get dropped too.
(5) If John Rough Contractor throws the level around like a shovel in his pickup after awhile the compensator hanging tapes in the auto level will stretch or even break. Then you have a real error of say 0.1 or 0.2 ft in 100 ft . ( 10 mm or 20 mm in 10 meters). If he drops the instrument hard you might get an gross huge error of 1 to 2 ft in 100 ft. (100 to 200mm in 10 meters)
(6) With a BIG bump the instrument's compensator will no long hang down correctly and the instrument cannot be aligned unless the compensator is replaced or restrung.
It is like if a 50 stone man sits on the children's swing set and the chains break or something gets stretched and the swing does not hang properly.
(7) Most auto levels get out of alignment by being abused. ie dropped or bumped hard. Lending one out is risky , folks often do not care.
(8) Auto levels used around concrete work often get concrete dust all over them. Sometimes the compensator gets stuck. Tilt the instrument slightly with a leveling screw towards you object to make sure the line of sight still is true. The "compensator" is the prism or mirror suspended inside that makes the level "shoot level" . It does this over a narrow range, when the bullseye vial bubble is sort of aligned. Many instruments will read true once the compensator is not stuck, ie you tap the instrument lightly.
(9) You can check you instrument by moving it and taking the same readings again. Lets say a buildings slab to be poured is is 10 meters by 20 meters.
Put the instrument in the center and measure the 4 corners heights to the corner boards. Let say they all are 1.50 meters . They all are the same distance from the level so any collimation/ slope error of the level does not matter.
Then move the instrument close to one corner, the same distance to the next two, and farthest for the last one.
You might get 1.498, 1.500 1,500 and 1.502.
Or you might get 1.45, 1.50, 1.55 meters if your instruments is way off.
thanks
More about survey and related. I love this vdo. This is amazing. Because I am an engineering student so this Vedio help me to improve my knowledge
Really great video, Jason.
thank you!! just had a class and was super lost. this cleared things up.
Its easy to calibrate level yourself.. do not trust a calibration shop.. I did it once and they screwed it up bad. The way to calibrate is pick two points 50 to 100 feet apart. Set the level within ten feet of one point-- shoot to the far point-- and then spin 180 to the close point-- measure the difference-- Than move the level to the far point in the same manner.. the differences should be the same.. To adjust-- turn the calibration screws one half the difference and check again.. Keep doing it until you get it so there is no error . I was a carpenter for 35 years. Never tighten down the levels adjustments to tight or you will bend or warp the table. Do not trust laser levels either until you check in the same manner.. Yes i have used bad lasers and level/transits. Also when you set up a level spin in 180 and 90 degrees to make sure it is level in all directions. Never assume any level tool is calibrated.. IT WILL COST YOU IF YOU DO SOONER OR LATTER.
Thank you for your insight!
The lectures have provided us full information on surveying so keep on giving us more
cool, thanks guys...i have an experiment tmrw..just like this one, the lecture was so boring but i got the whole concept in here.........thanks again
I'm reading the comments, wondering if they will be answered?
Helped me to recap the knowledge. Thanks
good work professor
How do one measure a distance between two points using the automatic level?
very hepfull
wondering if you can use height of collimation method given the reduced level of the last point.
Buenos tutoriales
He stated .001mm when I do believe it is .001 meters which is 1mm. He was measuring in meters to begin with.
Worse than that I only see graduation to the nearest .05 meters. The millimeter accuracy was on the back of the rod!!
Exactly... its actually 0.001m.
Can you do an experiment on fly leveling please 🙏
I was wonder why he added the two backside readings and then the foreside. Why did he add instead of subtracting the first two readings and then the second two and subtracting the results? But the arithmetic comes out the same. Abs-Bfs-[Bbs-Afs] is what I would have intuitively done, but that comes out to Abs-Bfs-Bbs+Afs=Abs+Afs-[Bfs+Bbs] same as he did.
The answer for me was solved by realizing that his 1st reading he calls a backsight this is toward the camera and at A, the second reading to point B he is calling a foresight (away from the camera). After he moves the tripod and takes a reading towards the camera at B which he called a backsight. The same direction now toward the camera and toward A is now called a Foresight (which I don't get why). Either way, if you subtract the first two reading A bs=1.148 and B fs=1.268 you get the true difference in height=0.120mm=absolute value|1.148-1.268|. If there is an error in level it would be some angle theta Up towards A say, but opposite down toward B or vice versa. If the distance from the tripod to A is the same as the distance to B, call it D, then the magnitude of the error would be D(tan(theta)). But one up, the other down so they cancel each other out.
So you have the true difference in height 0.120mm. He moves the tripod and measures the height relative the tripod again. This time both in the same direction, toward the camera. Now the errors don't cancel. He gets a difference now of 0.119mm=absolute value|1.284-1.165|.
That is different from the true difference by 0.001mm=0.120-0.119mm.
I don't know where the 16meters comes from that he uses for the average error over 16m but I suspect it's the distance from the second position of the tripod to A. Wish that was shown, however.
ua-cam.com/video/s4H0kJfbPAg/v-deo.html
Thank for this education.
Good on ya dave.
It was a lesson clean.. tks a lot!
that 1 mm error is not coming from the instrument itself but from the readings taken.
reading a 1.148 on a leveling rod means that third digit is just an approximation of the surveyor.. you should send your engineer's automatic level to a calibrating shop.
What is the acceptable error? Is there some official standard that define the acceptable error?
That calculation was very confusing, it wasn't explained what backsight and foresight are. Why can't you just say that the height differences measured from the two locations should be the same and if they aren't then the amount by which they differ is the error.
nice really helpful
Very helpful
I do realize that the metric system is superior, I suppose, however, that rod is confusing as heck to me. I'm going to go to my grave reading feet, tenths, and hundredths and do just fine.
How do we know the distance midpoint of two points
Clear as mud!
Hi .how can calibrate this camra?? Please guidance
you first recorded the point A on backsight and then point B on backsight when the station was moved beyond point B from the centre, and how is that waving the staff helpful for getting correct reading?
as u have moved the level to other position now doing this will change the height of instrument and this will affect the new levels?? taking levels from two different locations and adding them up? how can this be compared?/
+Har Oon yes he have already taked the reading he will substract the new from the old
I was wonder the same, I think, form what you saying. Why did he add instead of substract ?
Thank you sir❤
Thanks guys, very easy to remember, Jason needs more training though 😂
good video
What is the height of the instrument?
Why was Jason waving the levelling staff?
I supposed the levelling staff is to be held vertically for accuracy
nice
WhT position you should hold the staff for reading
I want to know also
I have a question. Must the pegs be of equal distance deep into the soil and out of it?
Adedeji Oludayo what's important is the pegs don't move. Pound them in so they don't move. Same as the steaks. If the ground is hard, use a tool, frost pin or cribbing pin to make a hole in the ground first to get your steak in. If you're Stakes blow over in the wind after you leave the site, you haven't done your job well and the people on that site won't want to have your Surveying Company back.
Wave the staff jason wave it boy 🤠🤠😎
😊😊
At 5:06 you say "2mm over 16m is quite acceptable", yet at 4:50 you said "0.001mm over 16m". Really? You didn't pick up these confusing mistakes in editing?
Unless I'm wrong, isn't it an error of 1mm (or 0.001m, not 0.001mm) over 16m? With an error of 2mm over 30m?
Also, could you please fix up the play list order? No wonder students, including myself, are confused.
The error is 0.001 meter
"In the middle of these two pigs ..."
Sure it is 0.001mm and not 0.001m error?
It should be 0.001m.
Least count of staff is 0.005m
Point ayeeeeee point boeeeeee
Point Buayeeeeeu
With respect, I ask permission to use this video clip as learning media, this video will be taught to students, used as a video to support education I hope you allow it, please reply to my request for permission
atay rag oten HAHAHAHA
who else came to the comments for "point buuuheeeee" ? lol
They call me nim kyyylleeee
The accuracy calculation should have been 0.001 metres (M) not 0.001 millimeters ( mm )
bui
0:41 for the point buuuhee jokes
A 8 metros y sin nivel para la mira, buena comprobación va a hacer, jajaja.
OTEN in our language means penis fyi.