This is a descriptive article on stable and unstable gravimeters. The article is mainly focused on LaCoste-Romberg and Worden gravimeters. Also, it includes marine gravity survey shortly.
Ambiguity in Geophysics,Gravity,Magnetic,EM,MT
Error reduction by Available applications
Geosoft,Euler,Anaylitical,Equpotential,Spectral, Principal Components
Definition
Geophysics is the application of method of physics to the
study of the earth.
On the other sense, it is a subject of natural science
concerned with the physical processes and the physical
properties of the earth and its surrounding space
environment and the use of co-ordinate methods for the
analysis.
It involves the application of physical theories and
measurements to discover the properties and processes of the
earth.
It covers seismic method, gravity method, electromagnetic method, magnetic method and radiometric method. all these methods help in mineral exploration
Ambiguity in Geophysics,Gravity,Magnetic,EM,MT
Error reduction by Available applications
Geosoft,Euler,Anaylitical,Equpotential,Spectral, Principal Components
Definition
Geophysics is the application of method of physics to the
study of the earth.
On the other sense, it is a subject of natural science
concerned with the physical processes and the physical
properties of the earth and its surrounding space
environment and the use of co-ordinate methods for the
analysis.
It involves the application of physical theories and
measurements to discover the properties and processes of the
earth.
It covers seismic method, gravity method, electromagnetic method, magnetic method and radiometric method. all these methods help in mineral exploration
Gravity and magnetic methods are an essential part of oil exploration. They do not replace seismic. Rather, they add to it. Despite being comparatively low-resolution, they have some very big advantages.
These geophysical methods passively measure natural variations in the earth’s gravity and magnetic fields over a map area and then try to relate these variations to geologic features in the subsurface. Lacking a controlled source, such surveys are usually environmentally unobjectionable.
The presentation comprises the Gravity Method, It's anomaly, reduction, and its applications. The Gravity method is commonly used in Geology specifically in Geophysics.
Gravity and magnetic methods are an essential part of oil exploration. They do not replace seismic. Rather, they add to it. Despite being comparatively low-resolution, they have some very big advantages.
These geophysical methods passively measure natural variations in the earth’s gravity and magnetic fields over a map area and then try to relate these variations to geologic features in the subsurface. Lacking a controlled source, such surveys are usually environmentally unobjectionable.
The presentation comprises the Gravity Method, It's anomaly, reduction, and its applications. The Gravity method is commonly used in Geology specifically in Geophysics.
A Possible Relationship between Gravitational Variations and Earthquakes in C...inventionjournals
An earthquake is not simply a sudden movement of the earth's crust, but the final product of a process that may have begun much earlier. In an area subject to tectonic stress, there can be precursory phenomena since this is where crustal deformation accumulates. A variation in gravity, measured instrumentally to the sixth decimal place, is one of the possible candidates to analyse measurable signals that precede, accompany and follow a seismic tremor. To verify the relationship between the number of earthquakes, the energy released, and the variations in gravity, the sequence in Central Italy was examined, above all that of January 2017. Data from a gravimeter located about 270 kilometres from the epicentral areas have been modelled as Standard Deviation, obtained from gravity measurements (400) carried out on the respective days. This indicator, of a statistical and mathematical nature, indicates the degree of dispersion with respect to its mean value, taken as the average value of these gravity measurements, and shows a positive correlation with the number of daily earthquakes and the energy released by the seismic sequence of January 2017.
Accelerometers
Accelerometers are devices that produce voltage signals proportional to the acceleration experienced. There are several techniques for converting acceleration to an electrical signal. The most general technique is described first and more recent techniques will be considered later.
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Cosmetic shop management system project report.pdfKamal Acharya
Buying new cosmetic products is difficult. It can even be scary for those who have sensitive skin and are prone to skin trouble. The information needed to alleviate this problem is on the back of each product, but it's thought to interpret those ingredient lists unless you have a background in chemistry.
Instead of buying and hoping for the best, we can use data science to help us predict which products may be good fits for us. It includes various function programs to do the above mentioned tasks.
Data file handling has been effectively used in the program.
The automated cosmetic shop management system should deal with the automation of general workflow and administration process of the shop. The main processes of the system focus on customer's request where the system is able to search the most appropriate products and deliver it to the customers. It should help the employees to quickly identify the list of cosmetic product that have reached the minimum quantity and also keep a track of expired date for each cosmetic product. It should help the employees to find the rack number in which the product is placed.It is also Faster and more efficient way.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
Learn about the cost savings, reduced environmental impact, and minimal disruption associated with trenchless technology. Discover detailed explanations of popular techniques such as pipe bursting, cured-in-place pipe (CIPP) lining, and directional drilling. Understand how these methods can be applied to various types of infrastructure, from residential plumbing to large-scale municipal systems.
Ideal for homeowners, contractors, engineers, and anyone interested in modern plumbing solutions, this guide provides valuable insights into why trenchless pipe repair is becoming the preferred choice for pipe rehabilitation. Stay informed about the latest advancements and best practices in the field.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
TECHNICAL TRAINING MANUAL GENERAL FAMILIARIZATION COURSEDuvanRamosGarzon1
AIRCRAFT GENERAL
The Single Aisle is the most advanced family aircraft in service today, with fly-by-wire flight controls.
The A318, A319, A320 and A321 are twin-engine subsonic medium range aircraft.
The family offers a choice of engines
COLLEGE BUS MANAGEMENT SYSTEM PROJECT REPORT.pdfKamal Acharya
The College Bus Management system is completely developed by Visual Basic .NET Version. The application is connect with most secured database language MS SQL Server. The application is develop by using best combination of front-end and back-end languages. The application is totally design like flat user interface. This flat user interface is more attractive user interface in 2017. The application is gives more important to the system functionality. The application is to manage the student’s details, driver’s details, bus details, bus route details, bus fees details and more. The application has only one unit for admin. The admin can manage the entire application. The admin can login into the application by using username and password of the admin. The application is develop for big and small colleges. It is more user friendly for non-computer person. Even they can easily learn how to manage the application within hours. The application is more secure by the admin. The system will give an effective output for the VB.Net and SQL Server given as input to the system. The compiled java program given as input to the system, after scanning the program will generate different reports. The application generates the report for users. The admin can view and download the report of the data. The application deliver the excel format reports. Because, excel formatted reports is very easy to understand the income and expense of the college bus. This application is mainly develop for windows operating system users. In 2017, 73% of people enterprises are using windows operating system. So the application will easily install for all the windows operating system users. The application-developed size is very low. The application consumes very low space in disk. Therefore, the user can allocate very minimum local disk space for this application.
Unstable/Astatic Gravimeters and Marine Gravity Survey
1. Unstable (astatic) Gravimeters
Description:
These instruments have an additional negative restoring force operating against the restoring
spring force, that is, in the same sense as Gravity. Since the 1930s, unstable gravimeters have
been used far more extensively than their stable counterparts. In a stable device, once the
system has been disturbed it will return to its original position, whereas an unstable device will
move further away from its original position. For example, if a pencil lying flat on a table is lifted
at one end and then allowed to drop, the pencil will return to being flat on the table. However,
if the pencil starts by being balanced on its end, once disturbed, it will fall over; i.e. it becomes
unstable, rather than returning to its rest position. The main point of the instability is to
exaggerate any movement, so making it easier to measure, and it is this principle on which the
unstable gravimeter is based. Various models of gravimeter use different devices to achieve the
instability.
The Principleof An Astatic Gravimeter:
An almost horizontal beam hinged at one end supports a mass at the other. The beam is
attached to a main spring which is connected at its upper end to a support above the hinge. The
spring attempts to pull the beam up anticlockwise by its turning moment, which is equal to the
restoring force in the spring multiplied by the perpendicular distance from the hinge (d). This
turning moment is balanced by the gravitational turning moment which attempts to rotate the
beam in a clockwise manner about the hinge and is equal to the weight of the mass (mg) times
the length of the beam (I) multiplied by the cosine of the angle of the beam from the horizontal
(i.e. mgl cos….). If gravity changes, the beam will move in response but will be maintained in its
new position because the main spring is a 'zero-length' spring. One virtue of such a spring is
that it is pretensioned during manufacture so that the tension in the spring is proportional to its
length. This means that if all forces were removed from the spring it would collapse to zero
length, something which is impossible in practice. Another virtue of the zero-length spring is
that it results in an instrument which is linear and very responsive over a wide range of gravity
values. Astatic gravimeters do not measure the movement of the mass in terms of changes in
gravity but require the displaced mass to be restored to a null position by the use of a
micrometer. The micrometer reading is multiplied by an instrumental calibration factor to give
values of gravity, normally to an accuracy within 0.1 g.u. 10.01 mGal) and in some specialist
devices to within 0.01 g.u. (0.001 mGal ).
2. Types:
There are many types of unstable gravimeter used for relative gravity measurement. Such as-
LaCoste and Romberg Gravimeter
Thyssen Gravimeter
Worden Gravimeter
Sodin Gravimeter
Vibrating String Gravimeter
Figure 1: Unstable or Astatic Gravimeter
3. LaCoste and Romberg Gravimeter
Description:
LaCoste and Romberg gravity meters were for a long time the state-of-the-art survey tool for
measuring the acceleration due to gravity. They are ‘relative’ meters (rather than ‘absolute’
meters) and are small enough for a single operator to manage.
The mechanism involves a beam, supported by a ‘zero-length’ spring at an angle of 45 degrees.
The meter is read by nulling the mass position, i.e., adding or subtracting a small amount of
force to restore it to a set position. This is achieved by rotating the large metal knob until the
beam is level. The reading is then simply read off the counter. It is a highly precise instrument;
the unit measures in milligals: one milligal is equivalent to 0.00001 meters per second squared.
Geophysicists use gravity surveys to investigate subsurface variations in density. Changes in
density due to different lithologies allow scientists to understand what is happening
underground. Gravity surveys are used for mineral, oil and gas exploration, civil engineering
applications, as well as a variety of environmental purposes.
The Principleof an LaCoste and Romberg Gravimeter:
A zero-length spring is one in which the tension is proportional to the actual length of the
spring, that is, if all external forces were removed the spring would collapse to zero length. The
advantage of the zero-length spring is that if it supports the beam and mass M (figure 2b) in the
horizontal position, it will support them in any position. Zero-length-springs are built with initial
tension so that a thresh-old force is required before spring extension begins(as with a door
spring).
To derive the expression for the sensitivity of this gravimeter, we write k(s-c) for the tension in
the spring when its length is s; thus, c is a small correction for the fact that the spring is not
truly zero length. Taking moments about the pivot in Figure 2b, we get
Mga cos 𝜃= k (s-c) b sin 𝛼
=k(s-c) b (y cos 𝜃)/s
Using the law of sines. Thus
g= (k/M) (b/a) (1-c/s) y
when g increases by δ g, the spring length increases by δ s where
δ g= (k/M) (b/a) (c/s) (y/s) δ s
4. For a given change in gravity δ g, we can make δ s as large as we wish by decreasing one or
more of the factors on the right-hand side; moreover, the closer the spring is to the zero-
length spring, the smaller c is and the larger δ s becomes.
In operation this is a null instrument, a second spring being used, which can be adjusted to
restore the beam to the horizontal position. The sensitivity of gravimeters in use in surface
exploration is generally 0.01 mGal. The instrument requires a constant temperature
environment, usually achieved by keeping it at a constant temperature that is higher than
the surroundings.
Figure 2: LaCoste and Romberg Gravimeter
(a) (b)
5. Worden Gravimeter
Gravimeters are extremely precise instruments that measure the earth’s gravity at a specific
location. Gravimeters are often used by prospectors to locate subterranean deposits of
valuable natural resources (mainly petroleum) as well as by geodesists to study the shape of the
earth and its gravitational field. Differences in topography, latitude, or elevation—as well as
differences in subterranean density—all affect the force of gravity. Commonly, gravimeters are
composed of a weight hanging on a zero-length spring inside a metal housing to negate the
influence of temperature and wind. Gravity is then measured by how much the weight
stretches the spring. Texas Instruments introduced the Pioneer gravimeter in 1960, describing it
as a Worden instrument "ideally suited for gravity programs in areas of limited latitude and
temperature variations." Its design is covered by three patents, all assigned to Texas
Instruments. One (#2,674,887), granted to Sam P. Worden in 1954, described an instrument
"which is of very simple construction and which, at the same time, will permit very delicate
measurements, and is smaller in size and of less weight and more rugged than conventional
types of gravity meters now in use." The patent went on to say that this instrument "is of such
construction and size that the working parts may be more efficiently insulated," and that it
incorporated "a compensating device which dispenses with the necessity of a thermostatic
control." The second patent (#2,738,676), granted to Worden and Boyd Cornelison in 1956,
described a "Large Range Gravity Sensitive Instrument." The third (#2,732,718) was granted to
Cornelison in 1956. Texas Instruments donated this example to the Smithsonian in 1963.
The Principleof Worden Gravimeter:
A simplified schematic is shown in figure 3.2. The moving system is similar to the LaCoste-
Romberg meter. The arm OP’ and beam OM are rigidly connected and pivot about O, changing
the length of the main spring P’C, which is fixed at C. We have the following relations:
∠OCP’= ∠OP’C = 𝜋/2 – ( 𝛼+ 𝜃/2)
RP ⊥ CP ; P’P ⊥ OP
So
RPP’ = 𝜋/2 – 𝛼
s=CP ; δ s= CP’-CP ≈ b𝜃 sin ( 𝜋/2 – 𝛼)
∴ 𝜃 ≈δ s/ (b cos 𝛼)
The correction factor c that appeared in the treatment of the LaCoste-Romberg meter is
negligible for the Worden meter. Taking moments about the pivot for the case where 𝜃 =0, we
get
6. Mga = ksb cos 𝛼
When g increases to (g+δ g), P movesalongthe circle toP’ and
M(g+ 𝛿g) a cos 𝜃= kb (s+ 𝛿s) cos ( 𝛼+ 𝜃/2)
When 𝜃=0, to the firstapproximationthisbecomes
M (g+ 𝛿g) = kb (s+ 𝛿s) {cos𝛼- ( 𝜃/2) sin 𝛼}
= kb (s+ 𝛿s) {cos𝛼- ( 𝛿s/2b) tan 𝛼}
= kb {s cos𝛼- 𝛿s(s/2b) tan 𝛼+ 𝛿s cos𝛼}
Subtracting the first moment equation to eliminate g, we get
Ma 𝛿g= kb {cos𝛼-(s/2b) tan 𝛼} 𝛿s
Using the relation sin 𝛼=(s/2b), we finally get
𝛿g = (k/m) (b/a) (cos2 𝛼/ cos 𝛼) 𝛿s
As in the LaCoste-Romberg meter, the sensitivity can be increased by decreasing the factors
(k/M) and (b/a); in addition, the factor (cos2𝛼/ cos𝛼) approaches zero when 𝛼 approaches 45
degree, thus furnishing another method of obtaining high sensitivity. In practice, the sensitivity
is about 0.01 mGal.
7. Figure 3.1: Worden Gravimeter
(a) (b)
Figure 3.2: Basic Principle of Worden Gravimeter
8. Marine Gravity Survey
Description:
Marine gravity measurements allow scientists to better understand the Earth's crust by
providing quantitative constraints on the structure of the crust and, in combination with other
co-registered data sets and forward models, improve our ability to interpret the geological
processes occurring within oceanic crust.
There are differentmethodsof surveyingmarine gravity.3typesof methodwill be discussedbelow to
overviewthe marine gravitysurveysystem
a) Locating marine stations: Considerable gravity has been done on the surface of water-
covered areas and also on the sea floor. Locating the marine station is usually done by using a
radio-navigation system such as Shoran, Raydist or RPS.
b) Remote control systems: Standard gravimeters have been adapted for operation on the sea
floor to depths of 200 m. this method of measurement is suitable for most unland waters and
coastal areas.
although the high sensitivity of this equipment is an advantage, operation in deep water is slow
because the assembly must be raised to the surface between stations.
c) Shipboard operations: Shipboard gravimeters are used for most gravity measurements at
sea. These meters are mounted on an elaborate gyro-stabilized platform located in the part on
a ship where there is minimum movement to roll and pitch.
Figure 4: Marine Gravity Survey
9. References:
1. Australian society of exploration geophysicists
2. https://www.aseg.org.au/equipment-museum/lacoste-and-romberg-
gravity-model-g-meter
3. "Worden" Gravity Meter Operating Instruction Manual No. 81537-4
(Houston: Texas Instruments, 1961)
4. https://learninglab.si.edu/resources/view/46222#more-info
5. National Museum of American History, Smithsonian Institution.
(2015, October 31). Smithsonian Learning Lab Resource: Worden
Gravimeter. Retrieved July 29, 2019.
6. An Introduction to Applied and Environmental Geophysics book,
copyright by John M. Reynolds in 1997, published by John wiley & sons
in 1997.
7. Applied Geophysics second edition published by the press syndicate of
the University of Cambridge.