RU2781761C1 - Method for controlling the accuracy of areal gravity survey - Google Patents

Abstract

FIELD: measuring technology.

SUBSTANCE: invention relates to methods for controlling the accuracy of areal gravity surveys. Essence: a sequential measurement of gravity is performed from a movable base using a gravimeter on parallel survey lines arranged with a uniform pitch. On the same area, model profiles oriented perpendicular to the survey lines are created with a pitch smaller than on the survey lines. The coordinates of the intersection points of each survey line with model profiles are found. Catalogs of gravimetric points of model profiles are formed, containing the coordinates of the intersection points of the survey lines with the model profiles and the magnitude of the gravity anomaly measured on the survey lines. High-frequency interference in gravity anomalies on model profiles are filtered. The difference between the measured anomaly value on the survey line and its filtered value on the line is determined at each intersection point, followed by the calculation of their variance. The accuracy of measurements on survey profiles is controlled by the value of the square root of the variance. The corrections are determined by calculating the average value of the differences on each survey line, followed by their introduction with the reverse sign into the measured gravity anomalies on each corresponding survey line. The variance of all differences over the entire area is calculated, followed by improved control of the accuracy of the square root of the variance.

EFFECT: improved control efficiency and accuracy of areal gravity surveys.

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Description

The invention relates to the field of geophysics and can be used to study the gravitational field of the Earth in order to solve scientific and practical problems.

A method for processing gravity survey data is known, comprising inputting measured potential field data from an aerial or marine survey of a potential field into a processor, said measured potential field data containing data defining a plurality of potential field measurements, each with a respective measurement position and measurement time; and determining by the processor said array of mapping field parameters by fitting said model to said measured potential field data, the model comprising a combination of a spatial part representing spatial variation of said potential field and a temporal part representing temporal noise in said measured potential field data (see Patent No. 2486549, 2008).

The disadvantage of this method is low efficiency due to the lack of control over the operation of devices in the process of shooting and the complexity of execution.

где Kgg, Kgz, Kzz - ковариационные матрицы значений ускорений силы тяжести, ускорения силы тяжести и глубины акватории, глубины акватории;The closest in technical essence to the proposed invention is a method of gravimetric survey of the water area, including driving the survey vessel along the planned tacks, while measuring the acceleration of gravity on the survey vessel with a gravimeter at points located along the survey tacks, determining the latitude ϕ and longitude λ of the place, the path P and absolute speed ν, calculation of the obtained data of the desired acceleration of gravity g _true , driving the ship along the planned tacks, the beginning and end of each of the tacks of which are closed to a reference hydrographic point or to two reference hydrographic points: the beginning of each tack - to one point, and the end of each tack - to another given point, an additional measurement on a moving vessel at points located along the survey lines, together with a measurement of the acceleration of gravity g _meas the depth of the water area Z _meas and the determination of geodetic rectangular coordinates x _i y _i , calculation of the true value of the acceleration of gravity g _true according to the formula:

where Kgg, Kgz, Kzz - covariance matrices of values of gravity accelerations, gravity accelerations and water area depth, water area depth;

где N - число пунктов, расположенных на расстоянии, равном радиусу корреляции значений

g_искi и Z_искi - искомые значения ускорения силы тяжести и глубины акватории соответственно в пунктах i-го галса с координатами x_i; Δg_этв - значения поправки за эффект Этвеша в пункте i:

и

- алгебраические полиномы, вычисление за эффект Этвеша Δg_этв по формуле:

если Земля представлена в виде шара, или по формуле:

если Земля представлена в виде земного эллипсоида, где:|G| - column vector of the original data

where N is the number of points located at a distance equal to the radius of correlation of values

g _isci and Z _isci are the desired values of the acceleration of gravity and the depth of the water area, respectively, at the points of the i-th tack with coordinates x _i ; Δg _etv - correction values for the Eötvös effect at point i:

and

- algebraic polynomials, calculation for the Eötvös effect Δg _etv by the formula:

if the Earth is represented as a sphere, or by the formula:

if the Earth is represented as an earth ellipsoid, where:

ω is the angular velocity of the Earth's rotation;

- абсолютная скорость движения съемочного судна; α - путь съемочного судна; R - радиус Земли; α и l - большая полуось и эксцентриситет земного эллипсоида;

и

- северная и восточная составляющие ϑH соответственно,

- absolute speed of the filming vessel; α - the path of the filming vessel; R is the radius of the Earth; α and l - semi-major axis and eccentricity of the earth's ellipsoid;

and

- northern and eastern components ϑH, respectively,

где i=1, 2, …, n - порядковый номер измеренных значений выбранных ускорений силы тяжести g_измi и глубин акватории Z_измi в чистых пунктах, расположенных на съемочном галсе;determination of the desired values of the acceleration of gravity g _isi and the depth of the water area Z _isi at the points of the i-th tack, free from constants, the calculation of systematic and periodically systematic errors with coordinates x _i , according to the formulas:

where i=1, 2, …, n is the serial number of the measured values of the selected accelerations of gravity g _meas and depths of the water area Z _meas in clean points located on the survey tack;

g _oA , g _oB and Z _oA , Z _oB - reference values of the acceleration of gravity and reference values of the depth of the water area at the locations of reference hydrographic points A and B, respectively;

k, n - the number of selected values of the acceleration of gravity and the depth of the water area on the segment of the survey line, limited by the reference hydrographic points A or B and the place E to the reference hydrographic points A and B, respectively (see RF patent No. 2575316, 2014).

The disadvantages of this method are the low accuracy of measuring the gravitational field of the Earth, because the measurement errors of the reference values of gravity at reference hydrographic points are not taken into account.

The technical result is to increase the efficiency of control and accuracy of areal gravimetric surveys by identifying and accounting for systematic and random errors due to the features of the device, the effects of disturbing physical factors and environmental conditions, increasing the reliability and productivity of gravimetric surveys while reducing additional costs.

, определение поправок путем вычисления среднего значения разностей δ_0i на каждом съемочном профиле i с последующим введением их с обратным знаком в измеренные аномалии силы тяжести на каждом соответствующем съемочном профиле i, вычисление дисперсии σ₁ всех разностей δ_ij - δ_0i по всей площади с последующим уточненным контролем точности по величине квадратного корня из дисперсии

.The technical result is achieved in a method for controlling the accuracy of an areal gravimetric survey, including successive measurement of gravity from a movable base by means of a gravimeter on survey parallel profiles i, located with a uniform step, followed by calculation of gravity anomalies, creation of model profiles oriented perpendicular to the survey profiles i on the same area. profiles j with a step less than on survey profiles i, finding the coordinates of the points of intersection of each survey profile i with model profiles j, the formation of catalogs of gravimetric points of model profiles j containing the coordinates of the points of intersection of survey profiles i with model j and the value measured on the survey profiles i gravity anomalies, filtering high-frequency interference in gravity anomalies on model profiles j, determining at each intersection point the difference δ _ij between the measured value of the anomaly on the survey profile i and its filtered value on profile j, with subsequent calculation of their variance σ, control of measurement accuracy on survey profiles i by the value of the square root of the variance

, determination of corrections by calculating the average value of the differences δ _0i on each survey profile i, followed by their introduction with the opposite sign into the measured gravity anomalies on each corresponding survey profile i, calculation of the variance σ _{1 of} all differences δ _ij - δ _0i over the entire area, followed by refined control of accuracy by the value of the square root of the variance

.

Creation of model profiles j oriented perpendicularly to survey profiles i with a step smaller than on survey profiles i allows performing areal gravimetric survey without performing additional measurements on secant survey profiles.

Finding the coordinates of the intersection points of each survey profile i with model profiles j, the formation of a catalog of gravimetric points of model profiles j, including the measurement time, the coordinates of the points of intersection of survey profiles i with model j and the magnitude of the anomaly obtained during measurements on survey profiles i allows you to build a special data configuration about anomalies of the gravitational field for their subsequent filtering.

Filtering high-frequency noise in gravity anomalies on model profiles j makes it possible to exclude high-frequency noise, into which the long-period noise of survey profiles i is converted.

позволяет получить величину погрешности измерений, включающую систематическую и случайную составляющие и, таким образом, произвести контроль точности выполненной площадной гравиметрической съемки.Determination at each intersection point of the difference δ _ij between the measured value of the anomaly on the survey profile i and its filtered value on the profile j, with subsequent calculation of their variance σ, control of the measurement accuracy on the survey profiles i by the value of the square root of the variance

allows you to get the measurement error, including systematic and random components and, thus, to control the accuracy of the performed areal gravimetric survey.

Determining the corrections by calculating the average value of the differences δ _0i on each survey profile i and then introducing them with the opposite sign into the measured gravity anomalies on each corresponding survey profile i allows taking into account the magnitude of the systematic error of each survey profile i.

позволяет получить величину остаточной случайной погрешности и произвести дополнительный контроль точности площадной гравиметрической съемки после уравнивания.Calculation of the variance σ _{1 of} all differences δ _ij - δ _0i over the entire area, followed by refined accuracy control by the value of the square root of the variance

allows you to get the value of the residual random error and perform additional control of the accuracy of the areal gravimetric survey after adjustment.

The way to control the accuracy of areal gravimetric survey is carried out as follows.

. Затем определяют поправки путем вычисления среднего значения разностей δ_0i на каждом съемочном профиле i и вводят их с обратным знаком в измеренные аномалии силы тяжести на каждом соответствующем съемочном профиле i. После чего вычисляют дисперсию σ₁ всех разностей δ_ij - δ_0i по всей площади и осуществляют уточненный контроль точности по величине квадратного корня из дисперсии

.Gravity is sequentially measured from the movable base of a sea or aircraft by means of a gravimeter on shooting parallel profiles i, arranged with a uniform step, and gravity anomalies are calculated. Model profiles j are built on the same area, oriented perpendicular to the shooting profiles i, with a step smaller than on the shooting profiles i. Find the coordinates of the points of intersection of each shooting profile i with model profiles j. Then catalogs of gravimetric points of model profiles j are formed, containing the coordinates of the points of intersection of survey profiles i with model j and the magnitude of the gravity anomaly measured on survey profiles i. After that, high-frequency noise is filtered in gravity anomalies on the model profiles j. The differences δ _ij between the measured value of the anomaly on the survey profile i and its filtered value on the profile j are determined at each intersection point, and the dispersion σ is calculated. Measurement accuracy control on survey profiles i is carried out by the value of the square root of the dispersion

. Corrections are then determined by calculating the average of the differences δ _0i on each survey profile i and inverting them into the measured gravity anomalies on each respective survey profile i. After that, the variance σ _{1 of} all differences δ _ij - δ _0i is calculated over the entire area and an accurate control of the accuracy is carried out by the value of the square root of the variance

.

A specific example of the implementation of the method for monitoring the accuracy of areal gravimetric survey.

A geophysical vessel with a displacement of 2500 tons performed an areal gravimetric survey along survey parallel profiles i in accordance with the accepted methodology by the aero-marine gravimetric complex "Chekan-AM". This gravimetric complex has the following characteristics:

- RMS measurement error 0.4 mGal.

- Disturbing acceleration range up to 100 Gal.

- Operating temperature range 10 - 25°С.

- Power consumption 270 W.

- Weight 78 kg.

As part of the areal gravimetric survey, measurements were made on 34 survey profiles parallel to each other i with a step of 4 km. The coordinate support was carried out by the GPS satellite navigation system. The time of work at the landfill was 24 days without interruption. According to inertial accelerations, the polygon can be divided into two almost equal parts. In the first half, they varied from 10 to 25 Gal, and in the second, due to weather changes, they reached 150 Gal. Regardless of the weather, the measurement conditions differed on the opposite courses of the ship's movement along the wave and against the wave.

182 model profiles j were created with a step smaller than the step of survey profiles i, equal to 1 km, oriented at right angles to survey profiles i. For each of the model profiles j, the coordinates and values of gravity anomalies at the points of intersection with all survey profiles i were determined. As a result, a network of model profiles j was obtained and catalogs of profiles j were formed, containing the coordinates of the points of intersection of survey profiles i with model profiles j, and the values of gravity anomalies measured on survey profiles i.

The noise frequency on the model profiles j is determined by the discreteness of the data, that is, the step of the survey profiles i, in this case, a step equal to 4 km, which is the basis for filtering gravity anomalies on the model profiles j. A moving average over five points was chosen as a filter. At the edges of the model profiles j, the value of the first or last approximating parabola was used.

Further, at all points of intersection of the survey i and model profiles j, the differences δ _ij were calculated between the values of the anomalies measured on the survey profiles i and the values of the anomalies filtered on the model profiles j. On survey profiles i, the difference δ _ij fluctuates around a certain level. This means that the weather conditions did not change during the measurements on each profile i and that this level can be taken into account as a constant correction for the entire profile i.

всех разностей δ_ij на полигоне представляет общую предварительную погрешность съемки до уравнивания. Полученная таким образом оценка погрешности съемки составила 0.705 мГал.Then the statistical characteristics of the differences δ_ij for all survey profiles i and for the polygon as a whole. As a result of filtering the model profiles j, the systematic errors in direct measurements are significantly suppressed, the average values of the differences δ_0ifor survey profiles i are their systematic errors, and the value of the square root of the variance

all differences δ_ij on the polygon represents the total preliminary survey error before adjustment. The estimate of the survey error thus obtained was 0.705 mGal.

According to the results of statistical processing of the differences δ _ij , the values of gravity anomalies on survey profiles i were equalized. It consists in the fact that a correction was introduced into all measurements of each survey profile i, equal to its systematic component (the average value of the differences) with the opposite sign δ _0i . As a result of such an adjustment, the systematic components on each survey profile i are excluded, which are random in the overall assessment of the survey as a whole.

. Полученная таким образом оценка погрешности съемки после введения поправок составила 0. 296 мГал.Next, the variance σ _{1 of} all differences δ _ij - δ _0i was calculated over the entire area of the polygon and an accurate control of the accuracy was performed by the value of the square root of the variance

. The estimate of the survey error obtained in this way after the introduction of corrections was 0.296 mGal.

Comparison of the results of this method with the results of standard processing using additional secant survey profiles i showed that for the areal survey of this polygon, the estimates obtained by the standard and proposed methods are 0.901 and 0.705 mGal, respectively, before the introduction of corrections, and after the introduction of corrections, 0.243 and 0.296 mGal, respectively. Therefore, the use of model profiles j in areal surveys makes it possible to evaluate the accuracy of measurements and control the execution of the survey, as well as to improve the accuracy only by taking into account the errors of individual profiles i without performing additional measurements on secant survey profiles, for example, if they are impossible to perform.

The proposed method allows to significantly improve the accuracy, reliability and productivity of areal gravimetric surveys and expand the geography of their production while reducing additional costs for their implementation. The proposed method can be useful for the rapid evaluation of measurements in the case when the control secant profiles are not performed for unforeseen reasons or will be performed much later.

Claims (1)

A method for controlling the accuracy of an areal gravimetric survey, including sequential measurement of gravity from a movable base by means of a gravimeter on survey parallel profiles

, located with a uniform step, followed by the calculation of gravity anomalies, the creation of survey profiles oriented perpendicular to the same area

model profiles

with a step smaller than on survey profiles

, finding the coordinates of the points of intersection of each survey profile

with model profiles

, formation of catalogs of gravimetric points of model profiles

, containing the coordinates of the intersection points of survey profiles

with model

and the value measured on survey profiles

gravity anomalies, filtering high-frequency noise in gravity anomalies on model profiles

, the definition at each point of intersection of the difference

between the measured value of the anomaly on the survey profile

and its filtered value on the profile

with subsequent calculation of their variance

, measurement accuracy control on survey profiles

by the square root of the variance

, determination of corrections by calculating the average value of the differences

on each shooting profile

with their subsequent introduction with the opposite sign into the measured gravity anomalies on each corresponding survey profile

, calculation of variance

all kinds

over the entire area, followed by a refined accuracy control by the square root of the variance

.