 Hello friends. Let me introduce myself first. Mr. SK Kulkarni, assistant professor at WIT Sholapur. Topic of our today's discussion is leveling need for inverted staff readings and precautions in calculation of reduced levels. Learning outcomes of today's session. At the end of this lecture, students will be able to explain need for inverted staff reading and precautions in calculations of reduced levels. Compute levels of required points using inverted staff readings and take arithmetic check. Introduction to inverted staff reading. When reduced a level of such a point is required, whose collimation plane table is at a higher position than the instrument position, then we have to go for inverted staff reading. Friends, that means what is done, staff is kept inverted in inverted manner. The bottom position of the staff is held touching to the point and this is called inverted staff reading, which are such points above the collimation plane level of instrument. These are soffits of a bridge, balcony, slab, chadja or beam. Now, here we can see inverted staff reading being taken in this particular image. This is a building whose canopy is projecting its RL. If you want to find, there is no alternative but to keep the staff in inverted manner like this. See here is the instrument collimation plane level. So, staff is held in what zero position of the staff will be touching to the point whose RL is required and the reading is taken. So, this is inverted staff reading. Now, what is the necessity of this inverted staff reading? Just we have discussed. When RLs of such points is required, which are at higher position than the collimation plane level of the instrument, then we have to take inverted staff reading and also we have discussed such points are RLs of soffits, beams, shafts and such judge. Instruments used for this purpose. There are different types of leveling instruments like dumpy level, tilting level, theodolite, total station and so many. We are using dumpy level for this particular part of the study and leveling staff is used to take the readings. It is a member whose height is generally 4 meters and readings are marked on it. It is held at the position whose RL is to be found and reading is recorded. Precautions to be taken during inverted staff readings. Inverted staff readings are treated as negative quantities remember and recorded accordingly because staff is held inverted and how it is held? Zero reading of the staff is kept touching to the point on the soffit remember. And one more thing is that through the telescope or through the telescope of the instrument inverted image of the part of the staff which is visible is available. So, what is done? Reading is taken from bottom to top so that we will get the correct reading. Here we can see inverted staff reading being taken. See here this is the slab its soffit is there and here inverted staff is held and reading is taken it is treated as negative reading. Here also we can see inverted reading negative. Now, let us see one example which will make many things clear to you. During the construction work the bottom of RCC beam was taken as a beam of RL 90.00 and the following notes were recorded. These are the notes reading first reading is on benchmark we know and it is inverted staff reading in this case. Then second reading is on page A on ground this is the reading and instrument is shifted now it is given. So, this is a change point then one more reading on the same staff position we know from the new instrument position we have to take one more reading on the same staff this is because change point this is again a backside reading and this is last reading at cornice B and you have to find RLs of all these points. So, first step will be preparing a level page of or level book page in this particular fashion remember the first column will be backside then second intermediate side third four side collimation plane level RL of particular point and then remarks this is the standard level page of a book. Now, first reading is always taken on a benchmark we know point whose RL is known. So, it is called benchmark. So, in remarks it will be written that the benchmark on beam sopidity in this case it is a beam sopita and it is given that staff was held inverted. And so, first reading is written in the backside column and it is treated as negative reading we can see and RL of point RL of benchmark is given as 90.00 it is recorded here. Now, the next reading which is the last reading from this instrument position remember. So, it will come in four side column you know four side reading will be the last reading in all intermediate readings will be intermediate side readings there is no intermediate side readings reading in this case it means. So, write down in four side column the next reading and write down here change point because here after the instrument position is changed and after changing position of the instrument one more reading from the same staff is to be taken from the changed instrument position. So, it is written in the same row as it is a backside it is written under backside. Now, last reading from this new instrument position is taken on cornice at B it is given and staff is held inverted it is also written. So, it will be negative reading and because last reading it will be written in the four side column. In this fashion the readings are recorded friends. Now, next step will be we have to set up here collimation plane level. Collimation plane level how to find collimation plane level RL of benchmark plus backside reading on benchmark will give you collimation plane level. So, here the calculations are done you can see here 90 plus it is negative reading. So, minus 2.87.765 is the collimation plane level here it is written here you can see. Now, how to find RL of next position next station collimation plane level minus subsequent reading will give you RL of that particular station. So, it is done and RL's are found here we can see RL of next station is 86.730 how the calculation is done 87.76 this is collimation plane level RL minus next reading 86.73 here it is written and now see here new instrument position is there. So, one more collimation plane level will have to be set because instrument position is changed. So, again same procedure RL of this station plus backside reading on that station will give you new collimation plane RL and here it is shown calculation is there 88.065. So, write down new collimation plane level. Now, here after this collimation plane level will be used to find RL of next point. So, 88.065 plus minus this is negative reading. So, it will be finally, 88.065 minus of minus plus 91.8 because subsequent reading is to be deducted you know right. So, addition of these two finally, becomes this much stop is inverted in the remarks column. Now, let us pause the file students here here are two questions for you solve them. First is why inverted stop reading is required to be taken? Second is how is inverted stop reading recorded in a level page book? These are the two questions you can solve them from the discussions which we have held up till now come on write your answers. So, why inverted stop reading is taken? Because when RL of such points is required which are at a higher position than the instrument position there is no alternative, but to take inverted stop reading right. And what is the method of recording these inverted stop readings? Inverted stop reading is recorded always as a negative reading because stop is inverted and which are such points RL of soffits of bridge beam slabs etc. Now, let us see one more important part that of arithmetic check. We have to check whether our calculations are correct or not by using this particular check. Remember this arithmetic check only gives idea about correctness of your calculations. It does not give any idea about correctness of your readings remember. So, for that purpose the arithmetic check which is there which is like this sigma back side minus sigma 4 side must be equal to last RL minus first RL. So, you have to check this and if check is not satisfied you have to revise the calculations remember right. If check is calculate satisfied no problem now here arithmetic check is taken summation of all the back sides minus summation of all the four sides comes to be plus 1.18 and last RL minus first RL comes to be again plus 1.18. So, this equation is satisfied that means arithmetic check is obtained and our calculations are correct no need of any revision here. These are the references of today's session please go through this. Thank you.