CN104457901A - Water depth determining method and system - Google Patents

Abstract

The invention provides a water depth determining method and system. The water depth determining method comprises the steps that the initial water depth is obtained; a first pressure sum caused by the sea surface atmospheric pressure and unit area sea water above the sea bottom at the initial moment, the initial pressure of a measurement instrument at the initial water depth position, a second pressure sum caused by the sea surface atmospheric pressure and the unit area sea water above the seat bottom at the terminal moment, and the terminal pressure of the measurement instrument at the terminal water depth position are obtained respectively; a difference value between the first pressure sum and the initial pressure is determined to obtain a first numerical value, and a difference value between the second pressure sum and the terminal pressure is determined to obtain a second numerical value; a difference value between the second numerical value and the first numerical value is determined to obtain a third numerical value; the ratio of the third numerical value to the product of the taken reference sea water density and the gravity acceleration parameter is determined to obtain vertical displacement; a difference value between the initial water depth and vertical displacement is determined to obtain the terminal water depth. By the adoption of the water depth determining method and system, errors produced during water depth determining are eliminated, and the depth of the measurement instrument relative to the mean sea level is directly obtained.

Description

A kind of method and system determining the depth of water

Technical field

The present invention relates to ocean dynamics technical field, more particularly, relate to a kind of method and system determining the depth of water.

Background technology

Oceanographic survey directly or indirectly carries out Investigational means to the physics of ocean, chemistry, biology, geology, geomorphology, meteorology i.e. other oceanic conditions with respective surveying instrument.In oceanographic survey, the accurate depth of water position of surveying instrument in ocean is that researchist conducts a research work, obtains the prerequisite of high-quality observation data.

On ocean circle, the conversion pressure generally by being measured by surveying instrument in ocean becomes the depth of water to come the exact position of computation and measurement instrument in ocean.The method of traditional marine bottom conversion pressure depth of water is the experimental formula of deriving based on hydrostatic equation and sea water state equation.Utilize the experimental formula of deriving, the pressure obtained the most at last is converted to the gained depth of water, the degree of depth that namely surveying instrument is surperficial to freely sea.

But existing method needs in derivation to consider that acceleration of gravity is along with the change of the depth of water and latitude and ocean temperature, salinity are on the impact of density of sea water.Because latitude does not change in time, latitude does not also just change in time on the impact of acceleration of gravity, but the temperature of seawater and salinity are larger over time, density of sea water also will change in time, namely all can there is error in each moment in the method for the existing pressure conversion depth of water, and this error changes over time.In actual measurement process, the Marine Environment Factors such as wave, tide and ocean current all can have an impact to the measurement of seawater pressure, and the depth of water that in existing method, pressure changes gained arrives the degree of depth on freely surface, sea into surveying instrument, the error therefore caused by these factors will directly affect last transformation result.

Summary of the invention

In view of this, the object of this invention is to provide and a kind ofly determine that the method and system of the depth of water are in order to obtain the degree of depth of accurate surveying instrument relative to surface, average sea.

To achieve these goals, the invention provides following technical scheme:

Determine a method for the depth of water, described method comprises:

Obtain the initial depth of water;

Obtain extra large the second pressure sum that the above unit area seawater of atmospheric pressure and seabed causes and the surveying instrument shown of the first pressure sum that initial time sea table atmospheric pressure and seabed above unit area seawater cause, the original pressure of surveying instrument in described initial water depths, end time respectively in the termination pressure stopping depth of water place;

Determine the difference of described first pressure sum and described original pressure respectively, obtain the first numerical value, the difference of described second pressure sum and described termination pressure, obtain second value;

Determine the difference of described second value and described first numerical value, obtain third value;

Determine the ratio of described third value and the reference density of sea water transferred and acceleration of gravity parameter multiplied result, obtain perpendicular displacement;

Determine the difference of the described initial depth of water and described perpendicular displacement, obtain the depth of water at described termination depth of water place.

Preferably, determine the difference of described second value and described first numerical value, obtain described third value according to the following equation:

$\begin{array}{c}\mathrm{\ΔP}\left(t\right)-\mathrm{\ΔP}\left(t_0\right)=({\∫}_{-D\left(t\right)}^{-h\left(t_0\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}-{\∫}_{-D\left(t_0\right)}^{-h\left(t_0\right)}\mathrm{\ρ}(t_0,z)g\left(z\right)\mathrm{dz})\\ +{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}\end{array}$

Wherein ,-D (t) is the depth of water, and ρ (t, z) is density of sea water, and g (z) is acceleration of gravity.

Preferably, be far smaller than a layer time scale relation for density of sea water change according to the time span that surveying instrument is measured, obtain the first discreet value of described third value according to the following equation:

$\begin{array}{c}\mathrm{\ΔP}\left(t\right)-\mathrm{\ΔP}\left(t_0\right)\≈{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}\\ \≈\mathrm{\ρ}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\Δh}\left(t\right)\\ +{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t_0,h\left(t_0\right))\mathrm{\Δg}\left(z\right)\mathrm{dz}+{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t,z)g\left(h\left(t_0\right)\right)\mathrm{dz}\\ +{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\Δ\ρ}(t,z)\mathrm{\Δg}\left(z\right)\mathrm{dz}\end{array}$

Wherein, the function that △ g (z) is the depth of water, △ ρ (t, z) is ocean temperature, the function of salinity and density.

Preferably, according to the variation relation of described perpendicular displacement △ h (t) scope and described △ g (z) and △ ρ (t, z), and the first discreet value of described third value, obtain described second discreet value according to the following equation:

$\mathrm{\ΔP}\left(t\right)-\mathrm{\ΔP}\left(t_0\right)\≈{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}\≈\mathrm{\ρ}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\Δh}\left(t\right).$

Preferably, described perpendicular displacement is obtained according to described second discreet value and following formula:

$\mathrm{\Δh}\left(t\right)\≈\frac{\mathrm{\ΔP}\left(t\right)-\mathrm{\ΔP}\left(t_0\right)}{\mathrm{\ρ}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}.$

Preferably, described method also comprises:

Obtain the 3rd discreet value, described 3rd discreet value is for determining the discreet value of described perpendicular displacement.

Preferably, described 3rd discreet value of described acquisition comprises:

Determine one with the ratio of the expression formula multiplied result of described density of sea water and described acceleration of gravity;

Described reciprocal value is carried out first order Taylor expansion, obtains the 3rd discreet value of described inverse according to the following equation:

$\begin{array}{c}\frac{1}{\mathrm{\ρ}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}=\frac{1}{({\mathrm{\ρ}}_0+\mathrm{\Δ\ρ}(t_0,h\left(t_0\right)))(g_0+\mathrm{\Δg}\left(h\left(t_0\right)\right))}\\ \≈(\frac{1}{{\mathrm{\ρ}}_0}-\frac{\mathrm{\Δ\ρ}(t_0,h\left(t_0\right))}{{{\mathrm{\ρ}}_0}^2}+O\left({\mathrm{\Δ\ρ}}^2(t_0,h\left(t_0\right))\right))\×(\frac{1}{g_0}-\frac{\mathrm{\Δg}\left(h\left(t_0\right)\right)}{{g_0}^2}+O\left({\mathrm{\Δg}}^2\left(h\left(t_0\right)\right)\right))\\ \≈(\frac{1}{{\mathrm{\ρ}}_0{g}_0}-\frac{\mathrm{\Δ\ρ}(t_0,h\left(t_0\right))}{{{\mathrm{\ρ}}_0}^2{g}_0}-\frac{\mathrm{\Δg}\left(h\left(t_0\right)\right)}{{\mathrm{\ρ}}_0{g_0}^2}+\frac{\mathrm{\Δ\ρ}(t_0,h\left(t_0\right))\mathrm{\Δg}\left(h\left(t_0\right)\right)}{{{\mathrm{\ρ}}_0}^2{g_0}^2})\\ +O({\mathrm{\Δ\ρ}}^2(t_0,h\left(t_0\right)),{\mathrm{\Δg}}^2\left(h\left(t_0\right)\right))\\ \≈\frac{1}{{\mathrm{\ρ}}_0{g}_0}\end{array}.$

Determine a system for the depth of water, described system comprises:

First acquiring unit, for obtaining the initial depth of water;

Second acquisition unit, for obtaining extra large the second pressure sum that the above unit area seawater of atmospheric pressure and seabed causes and the surveying instrument shown of the first pressure sum that initial time sea table atmospheric pressure and seabed above unit area seawater cause, the original pressure of surveying instrument in described initial water depths, end time respectively in the termination pressure stopping depth of water place;

First determining unit, for determining the difference of described first pressure sum and described original pressure respectively, obtains the first numerical value, determines the difference of described second pressure sum and described termination pressure, obtains second value;

Second determining unit, for determining the difference of described second value and described first numerical value, obtains third value;

4th acquiring unit, for determining the ratio of described third value and the reference density of sea water transferred and acceleration of gravity parameter multiplied result, obtains perpendicular displacement;

3rd determining unit, for determining the difference of the described initial depth of water and described perpendicular displacement, obtains the depth of water at described termination depth of water place.

Preferably, described system also comprises:

First estimates unit, is far smaller than the time scale relation of density of sea water change, obtains the first discreet value of described third value according to the following equation according to the time span of surveying instrument measurement:

$\begin{array}{c}\mathrm{\ΔP}\left(t\right)-\mathrm{\ΔP}\left(t_0\right)\≈{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}\\ \≈{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}(\mathrm{\ρ}(t_0,h\left(t_0\right))+\mathrm{\Δ\ρ}(t,z))(g\left(h\left(t_0\right)\right)+\mathrm{\Δg}\left(z\right))\mathrm{dz}\\ \≈{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}(\mathrm{\ρ}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)+\mathrm{\ρ}(t_0,h\left(t_0\right))\mathrm{\Δg}\left(z\right)+\mathrm{\Δ\ρ}(t,z)g\left(h\left(t_0\right)\right)+\mathrm{\Δ\ρ}(t,z)\mathrm{\Δg}\left(z\right))\mathrm{dz}\\ \≈\mathrm{\ρ}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\Δh}\left(t\right)\\ +{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t_0,h\left(t_0\right))\mathrm{\Δg}\left(z\right)\mathrm{dz}+{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\Δ\ρ}(t,z)g\left(h\left(t_0\right)\right)\mathrm{dz}\\ +{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\Δ\ρ}(t,z)\mathrm{\Δg}\left(z\right)\mathrm{dz}\end{array}$

Wherein, the function that △ g (z) is the depth of water, the function of △ ρ (t, z) position ocean temperature, salinity and density;

Second estimates unit, for according to described perpendicular displacement △ h (t) scope and described △ g (z) and △ ρ (t, z) variation relation, and the first discreet value of described third value, obtain described second discreet value according to the following equation:

$\mathrm{\ΔP}\left(t\right)-\mathrm{\ΔP}\left(t_0\right)\≈{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}\≈\mathrm{\ρ}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\Δh}\left(t\right);$

3rd estimates unit, for determining the discreet value of described perpendicular displacement.

Preferably, the described 3rd estimate unit and comprise:

First computing unit, for determining the inverse of the expression formula multiplied result of density of sea water and acceleration of gravity;

Second computing unit, for described reciprocal value is carried out first order Taylor expansion, obtains the 3rd discreet value of described inverse according to the following equation:

$\begin{array}{c}\frac{1}{\mathrm{\ρ}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}=\frac{1}{({\mathrm{\ρ}}_0+\mathrm{\Δ\ρ}(t_0,h\left(t_0\right)))(g_0+\mathrm{\Δg}\left(h\left(t_0\right)\right))}\\ \≈(\frac{1}{{\mathrm{\ρ}}_0}-\frac{\mathrm{\Δ\ρ}(t_0,h\left(t_0\right))}{{{\mathrm{\ρ}}_0}^2}+O\left({\mathrm{\Δ\ρ}}^2(t_0,h\left(t_0\right))\right))\×(\frac{1}{g_0}-\frac{\mathrm{\Δg}\left(h\left(t_0\right)\right)}{{g_0}^2}+O\left({\mathrm{\Δg}}^2\left(h\left(t_0\right)\right)\right))\\ \≈(\frac{1}{{\mathrm{\ρ}}_0{g}_0}-\frac{\mathrm{\Δ\ρ}(t_0,h\left(t_0\right))}{{{\mathrm{\ρ}}_0}^2{g}_0}-\frac{\mathrm{\Δg}\left(h\left(t_0\right)\right)}{{\mathrm{\ρ}}_0{g_0}^2}+\frac{\mathrm{\Δ\ρ}(t_0,h\left(t_0\right))\mathrm{\Δg}\left(h\left(t_0\right)\right)}{{{\mathrm{\ρ}}_0}^2{g_0}^2})\\ +O({\mathrm{\Δ\ρ}}^2(t_0,h\left(t_0\right)),{\mathrm{\Δg}}^2\left(h\left(t_0\right)\right))\\ \≈\frac{1}{{\mathrm{\ρ}}_0{g}_0}\end{array};$

4th determining unit, the discreet value of described perpendicular displacement is determined according to described 3rd discreet value and following formula:

$\mathrm{\Δh}\left(t\right)\≈\frac{\mathrm{\ΔP}\left(t\right)-\mathrm{\ΔP}\left(t_0\right)}{{\mathrm{\ρ}}_0{g}_0}.$

Compared with prior art, advantage of the present invention is as follows:

Provided by the inventionly determine that the method for the depth of water simply and easily realizes, by the initial depth of water and initial time and in the termination time perpendicular displacement subtract each other, eliminate and to determine in depth of water process, due to the error that the environmental factors such as wave, tide and ocean current cause, directly to obtain the degree of depth of surveying instrument relative to mean sea level.Determine the error in depth of water method not along with the change of time changes due to provided by the invention, therefore this error is foreseeable.

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only embodiments of the invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to the accompanying drawing provided.

A kind of a kind of process flow diagram determining the method for the depth of water that Fig. 1 provides for the embodiment of the present invention;

A kind of another kind of process flow diagram determining the method for the depth of water that Fig. 2 provides for the embodiment of the present invention;

A kind of a kind of structural representation determining the system of the depth of water that Fig. 3 provides for the embodiment of the present invention;

A kind of another kind of structural representation determining the system of the depth of water that Fig. 4 provides for the embodiment of the present invention;

A kind of kernel texture schematic diagram determining the system of the depth of water that Fig. 5 provides for the embodiment of the present invention.

Embodiment

Below in conjunction with the accompanying drawing in the embodiment of the present invention, be clearly and completely described the technical scheme in the embodiment of the present invention, obviously, described embodiment is only the present invention's part embodiment, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

Please refer to Fig. 1, embodiments provide a kind of a kind of process flow diagram determining the method for the depth of water, can comprise the following steps:

Step 100: obtain the initial depth of water.

Step 101: obtain extra large the second pressure sum that the above unit area seawater of atmospheric pressure and seabed causes and the surveying instrument shown of the first pressure sum that initial time sea table atmospheric pressure and seabed above unit area seawater cause, the original pressure of surveying instrument in initial water depths, end time respectively in the termination pressure stopping depth of water place.

Step 102: the difference determining the first pressure sum and original pressure respectively, obtains the first numerical value, determines the difference of the second pressure sum and termination pressure, obtains second value.

Step 103: the difference determining second value and the first numerical value, obtains third value.

Step 104: the ratio determining third value and the reference density of sea water transferred and acceleration of gravity parameter multiplied result, obtains perpendicular displacement.

Step 105: the difference determining the initial depth of water and perpendicular displacement, obtains the depth of water stopping depth of water place.

The method determining the depth of water provided by the invention, by the initial depth of water and initial time and method that in the termination time, perpendicular displacement is subtracted each other, eliminates and is determining the error in depth of water process, directly obtain the degree of depth of surveying instrument relative to mean sea level.Determine the error in depth of water method not along with the change of time changes due to provided by the invention, therefore this error is foreseeable.

Please refer to Fig. 2, it illustrates a kind of another kind of process flow diagram determining the method for the depth of water that the embodiment of the present invention provides, can comprise the following steps:

Step 200: obtain the initial depth of water.

Setting the initial depth of water is h (t ₀), wherein initial depth of water h (t ₀) can by LP method or determining in the position that anchor is fastened of laying at initial time according to surveying instrument.

It should be noted that, LP method is corrected item to realize by adding one.

Step 201: obtain extra large the second pressure sum that the above unit area seawater of atmospheric pressure and seabed causes and the surveying instrument shown of the first pressure sum that initial time sea table atmospheric pressure and seabed above unit area seawater cause, the original pressure of surveying instrument in initial water depths, end time respectively in the termination pressure stopping depth of water place.

Wherein, first pressure sum is by sitting bottom pressure sensor measurement, specifically pressure transducer be placed in seabed or equip close to the investigation in seabed, because marine bottom is less by the impact of environmental factor, the seat bottom pressure meter sat in bottom pressure sensor accurately can measure the SEA LEVEL VARIATION of monitoring point, therefore sits bottom pressure sensor and can measure and stop the depth of water accurately.It should be noted that, the acquisition methods of the second pressure sum is identical with the acquisition methods of the first pressure sum.

By moment t ₀be set to initial time, wherein at initial time, the pressure sat measured by bottom pressure sensor is sea table atmospheric pressure P _athe pressure sum P caused with the above unit area seawater in seabed _b(t ₀).Due to P _-ht () represents the pressure that the depth of water utilizes acoustic Doppler fluid velocity profile instrument (ADCP.Acoustic Doppler CurrentProfiler), conductivity-temperature-depth system (Conductivity Temperature and Pressure) or other surveying instruments to obtain for-h (t) place.Namely at the initial depth of water-h (t ₀) place, the original pressure obtained in initial water depths by surveying instrument is P _-h(t ₀).

Step 202: the difference determining the first pressure sum and original pressure respectively, obtains the first numerical value, determines the difference of the second pressure sum and termination pressure, obtains second value.

Step 203: the difference determining second value and the first numerical value, obtains third value.

Step 204: the first discreet value obtaining third value.

Step 205: obtain the second discreet value.

Step 206: obtain perpendicular displacement according to the second discreet value.

Step 207: obtain the 3rd discreet value, the 3rd discreet value is for determining the discreet value of perpendicular displacement.

It should be noted that, the acquisition of the 3rd discreet value can realize in the following way:

One is the inverse of the expression formula multiplied result determining density of sea water and acceleration of gravity.

Two is that reciprocal value is carried out first order Taylor expansion, and makes first approximation to the formula carrying out Taylor expansion, just can obtain the 3rd discreet value estimated.

Step 208: the difference determining the initial depth of water and perpendicular displacement, obtains the depth of water stopping depth of water place.

Wherein, what the present invention obtained is the degree of depth of surveying instrument relative to surface, average sea, and relative to the degree of depth on the surface, freely sea got in prior art, the water depth value at the termination depth of water place that the present invention gets is more accurate.

It should be noted that, when not considering Pressure Sensor Precision, sitting the pressure P that bottom pressure sensor is surveyed _bfor sea table atmospheric pressure P _athe pressure sum caused with the above unit area seawater in seabed, its expression formula is:

$P_b\left(t\right)=P_a\left(t\right)+{\∫}_{-D\left(t\right)}^{\mathrm{\η}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}---\left(1\right)$

Wherein, η (t) represents that sea level height rises and falls, and ρ (t, z) represents density of sea water, and g (z) represents acceleration of gravity.

When the depth of water is-h (t), utilize the pressure P that surveying instrument records _-ht the expression formula of () is:

$P_{-h}\left(t\right)=P_a\left(t\right)+{\∫}_{-h\left(t\right)}^{\mathrm{\η}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}---\left(2\right)$

Wherein, h (t) is for surveying instrument is relative to the depth of water of mean sea level.

Wherein, above-mentioned surveying instrument can adopt ADCP or CTD, other surveying instruments also can be adopted to carry out pressure survey simultaneously.

Utilize formula (2) to deduct formula (1), obtain formula:

$\mathrm{\ΔP}\left(t\right)=P_b\left(t\right)-P_{-h}\left(t\right)={\∫}_{-D\left(t\right)}^{-h\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}---\left(3\right)$

Wherein, the expression formula of depth of water h (t) is:

h(t)＝h(t ₀)-△h(t) (4)

Wherein, h (t ₀) be t=t ₀the depth of water at moment surveying instrument place, △ h (t) is for surveying instrument is relative to t=t ₀the perpendicular displacement in moment.

When surveying instrument is fixed on marine mooring system, owing to being subject to the impact of horizontal ocean current, surveying instrument will produce motion in the horizontal direction.Again because anchor system is anchored on seabed, therefore surveying instrument will produce the displacement of vertical direction, i.e. perpendicular displacement again while producing motion in the horizontal direction.

Formula (4) is deducted formula (3), obtains:

$\mathrm{\ΔP}\left(t\right)={\∫}_{-D\left(t\right)}^{-h\left(t_0\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}+{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}---\left(5\right)$

By t=t ₀, substitute into formula (5), obtain:

$\mathrm{\ΔP}\left(t_0\right)={\∫}_{-D\left(t_0\right)}^{-h\left(t_0\right)}\mathrm{\ρ}(t_0,z)g\left(z\right)\mathrm{dz}---\left(6\right)$

Utilize formula (5) to deduct formula (6), obtain:

$\begin{array}{c}\mathrm{\ΔP}\left(t\right)-\mathrm{\ΔP}\left(t_0\right)=({\∫}_{-D\left(t\right)}^{-h\left(t_0\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}-{\∫}_{-D\left(t_0\right)}^{-h\left(t_0\right)}\mathrm{\ρ}(t_0,z)g\left(z\right)\mathrm{dz})\\ +{\∫}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\Δh}\left(t\right)}\mathrm{\ρ}(t,z)g\left(z\right)\mathrm{dz}\end{array}---\left(7\right)$

Because marine bottom ocean current is more weak, marine stream slowly, therefore can think that sitting bottom pressure meter remains on a fixing depth of water (usually only having the change of several meters), and namely D (t) is constant.

Suppose t-t ₀< < T, the time span that surveying instrument is measured is far smaller than the time scale of density of sea water change, therefore in formula (7), the Section 1 on the right can be ignored, and can obtain the first discreet value.

Because the expression formula of the density p (t, z) of seawater and the g (z) of gravity acceleration can be written as respectively:

ρ(t,z)＝ρ(t ₀,h(t ₀))+△ρ(t,z) (8)

g(z)＝g(h(t ₀))+△g(z) (9)

Wherein, ρ (t _0,h (t ₀)) represent initial time depth of water h (t ₀) density of sea water at place; G (h (t ₀)) represent initial time depth of water h (t ₀) acceleration of gravity at place.

Formula (8) and formula (9) are substituted into formula (7), and the expression formula obtaining Section 2 in formula (7) is:

$\begin{array}{c}{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}={\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}(\mathrm{\&rho;}(t_0,h\left(t_0\right))+\mathrm{\&Delta;\&rho;}(t,z))(g\left(h\left(t_0\right)\right)+\mathrm{\&Delta;g}\left(z\right))\mathrm{dz}\\ ={\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}(\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)+\mathrm{\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(z\right)+\mathrm{\&Delta;\&rho;}(t,z)g\left(h\left(t_0\right)\right)+\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right))\mathrm{dz}\\ =\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right)\\ +{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}+{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)g\left(h\left(t_0\right)\right)\mathrm{dz}+{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}\end{array}---\left(10\right)$

Wherein, a fixing position, △ g (z) is only the function of the depth of water, and the change of every meter is about 1.092*10 ^-6m*s ^-2.According to sea water state equation, △ ρ (t, z) is ocean temperature, the function of salinity and density.When the perpendicular displacement change of surveying instrument is less than 10 meters of magnitudes, the variation range of △ ρ (t, z) and △ g (z) is respectively: 10kg*m ^-3with 10 ^-4m*s ^-2.

Compared with Section 1 in formula (10), its last three can be estimated as:

${\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}/\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right)\&ap;\frac{\mathrm{\&Delta;g}\left(z\right)}{g\left(h\left(t_0\right)\right)}<{10}^{-5}---\left(11\right)$

${\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)g\left(h\left(t_0\right)\right)\mathrm{dz}/\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right)\&ap;\frac{\mathrm{\&Delta;\&rho;}(t,z)}{\mathrm{\&rho;}(t_0,h\left(t_0\right))}<{10}^{-2}---\left(12\right)$

${\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}/\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right)\&ap;\frac{\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right)}{\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}<{10}^{-7}---\left(13\right)$

Error caused by last three is 1% to the maximum, ignores error term, can obtain the second discreet value, be shown below:

${\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}\&ap;\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right)---\left(14\right)$

Formula (14) is substituted into formula (7) can obtain:

$\mathrm{\&Delta;h}\left(t\right)\&ap;\frac{\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)}{\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}\&ap;\frac{(P_b\left(t\right)-P_{-h}\left(t\right))-(P_b\left(t_0\right)-P_{-h}\left(t_0\right))}{\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}---\left(15\right)$

Therefore,

$h\left(t\right)\&ap;h\left(t_0\right)-\mathrm{\&Delta;h}\left(t\right)\&ap;h\left(t_0\right)-\frac{(P_b\left(t\right)-P_{-h}\left(t\right))-(P_b\left(t_0\right)-P_{-h}\left(t_0\right))}{\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}---\left(16\right)$

In formula (16), ρ (t ₀, h (t ₀)) and g (h (t ₀)) can be written as respectively:

ρ(t ₀,h(t ₀))＝ρ ₀+△ρ(t ₀,h(t ₀)) (17)

g(h(t ₀))＝g ₀+△g(h(t ₀)) (18)

Wherein ρ ₀=1020kg*m ^-3and g ₀=9.8m*s ^-2be respectively with reference to density of sea water and acceleration of gravity.

Formula (17) and formula (18) are substituted into the Section 2 on the right in formula (16), utilize first order Taylor formula to launch to obtain simultaneously:

$\begin{array}{c}\frac{1}{({\mathrm{\&rho;}}_0+\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right)))(g_0+\mathrm{\&Delta;g}(h\left(t_0\right)))}=(\frac{1}{{\mathrm{\&rho;}}_0}-\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))}{{\mathrm{\&rho;}}_0^2}+O\left({\mathrm{\&Delta;\&rho;}}^2(t_0,h\left(t_0\right))\right))\\ \&times;(\frac{1}{g_0}-\frac{\mathrm{\&Delta;g}\left(j\left(t_0\right)\right)}{g_0^2}+O\left({\mathrm{\&Delta;g}}^2\left(h\left(t_0\right)\right)\right))\\ =(\frac{1}{{\mathrm{\&rho;}}_0{g}_0}-\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))}{{\mathrm{\&rho;}}_0^2{g}_0}-\frac{\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{\mathrm{\&rho;}}_0{g}_0^2}\\ +\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{\mathrm{\&rho;}}_0^2{g}_0^2})\\ +O({\mathrm{\&Delta;\&rho;}}^2(t_0,h\left(t_0\right)),{\mathrm{\&Delta;g}}^{2}h\left(t_0\right)))\end{array}---\left(19\right)$

In ocean, ρ (t ₀, h (t ₀)) and g (h (t ₀)) variation range be respectively 20kg*m ^-3and 0.1m*s ^-2.In formula (19), the estimation expression formula of single order item is respectively:

$-\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))}{{\mathrm{\&rho;}}_0^2{g}_0}/\frac{1}{{\mathrm{\&rho;}}_0{g}_0}=-\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))}{{\mathrm{\&rho;}}_0}<2\&times;{10}^{-2}---\left(20\right)$

$-\frac{\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{\mathrm{\&rho;}}_0{g}_0^2}/\frac{1}{{\mathrm{\&rho;}}_0{g}_0}=-\frac{\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{g_0}<{10}^{-2}---\left(21\right)$

$\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{\mathrm{\&rho;}}_0^2{g}_0^2}/\frac{1}{{\mathrm{\&rho;}}_0{g}_0}=\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{\mathrm{\&rho;}}_0{g}_0}<{10}^{-4}---\left(22\right)$

Wherein, in formula (20), (21), (22), the maximum error of single order item is 3%, ignores the error caused by density of sea water and acceleration of gravity, obtains the 3rd discreet value, be shown below:

$\frac{1}{({\mathrm{\&rho;}}_0+\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right)))(g_0+\mathrm{\&Delta;g}\left(h\left(t_0\right)\right))}\&ap;\frac{1}{{\mathrm{\&rho;}}_0{g}_0}---\left(23\right)$

Composite type (15) and formula (23) namely obtain the discreet value of perpendicular displacement, are shown below:

$\mathrm{\&Delta;h}\left(t\right)\&ap;\frac{(P_b\left(t\right)-P_{-h}\left(t\right))-(P_b\left(t_0\right)-P_{-h}\left(t_0\right))}{{\mathrm{\&rho;}}_0{g}_0}---\left(24\right)$

The expression formula to sum up obtaining the depth of water stopping depth of water place is:

$h\left(t\right)\&ap;h\left(t_0\right)-\frac{(P_b\left(t\right)-P_{-h}\left(t\right))-(P_b\left(t_0\right)-P_{-h}\left(t_0\right))}{{\mathrm{\&rho;}}_0{g}_0}---\left(25\right)$

Wherein, initial depth of water h (t ₀) or can be placed at initial time cloth the position that anchor fastens according to surveying instrument and determine by LP method.

Therefore, according to formula (25), if given t sits the pressure of bottom pressure sensor and surveying instrument, just surveying instrument place depth of water h (t) can be obtained.

The method of the determination depth of water that the embodiment of the present invention provides, carry out utilizing the method, in the process of the marine bottom conversion pressure ocean depth of water, utilizing linear perturbation theory to carry out theory deduction, predictor error, directly obtain the depth of water relative to mean sea level, reduce environmental factor to the impact calculated.The error that wherein the initial depth of water causes is an offset error, can not change in computation process along with the change of time.When the initial depth of water gives timing, the density of sea water that the error of above method is mainly derived from surveying instrument displacement in the vertical direction and causes and the change that gravity accelerates, the relative error caused according to the known perpendicular displacement of above-mentioned theoretical analysis can not more than 4%, and this error does not change over time.

Corresponding with said method embodiment, the embodiment of the present invention additionally provides a kind of system determining the depth of water, be applied in oceanographic survey, determine that the structural representation of the system of the depth of water please refer to shown in Fig. 3, comprising: the first acquiring unit 11, second acquisition unit 12, first determining unit 13, second determining unit 14, the 3rd acquiring unit 15 and the 3rd determining unit 16.Wherein:

First acquiring unit 11, for obtaining the initial depth of water.

Setting the initial depth of water is h (t ₀), wherein initial depth of water h (t ₀) or can be placed at initial time cloth the position that anchor fastens according to surveying instrument and determine by LP method.

It should be noted that, LP method is corrected item to realize by adding one.

Second acquisition unit 12, for obtaining extra large the second pressure sum that the above unit area seawater of atmospheric pressure and seabed causes and the surveying instrument shown of the first pressure sum that initial time sea table atmospheric pressure and seabed above unit area seawater cause, the original pressure of surveying instrument in described initial water depths, end time respectively in the termination pressure stopping depth of water place.

Wherein, first pressure sum is by sitting bottom pressure sensor measurement, specifically pressure transducer be placed in seabed or equip close to the investigation in seabed, because marine bottom is less by the impact of environmental factor, the seat bottom pressure meter sat in bottom pressure sensor accurately can measure the SEA LEVEL VARIATION of monitoring point, therefore sits bottom pressure sensor and can measure and stop the depth of water accurately.In like manner, the obtain manner of the second pressure sum is identical with the obtain manner of the first pressure sum.

First determining unit 13, for determining the difference of the first pressure sum and original pressure respectively, obtains the first numerical value, determines the difference of the second pressure sum and termination pressure, obtains second value.

Second determining unit 14, for determining the difference of second value and the first numerical value, obtains third value.

3rd acquiring unit 15, for determining the ratio of third value and the reference density of sea water transferred and acceleration of gravity parameter multiplied result, obtains perpendicular displacement.

3rd determining unit 16, for determining the difference of the initial depth of water and perpendicular displacement, obtains the depth of water stopping depth of water place.

Provided by the inventionly determine that the method for the depth of water simply and easily realizes, by the initial depth of water and initial time and in the termination time perpendicular displacement subtract each other, eliminate and to determine in depth of water process, due to the error that the environmental factors such as wave, tide and ocean current cause, directly to obtain the degree of depth of surveying instrument relative to mean sea level.Determine the error in depth of water method not along with the change of time changes due to provided by the invention, therefore this error is foreseeable.

Please refer to Fig. 4, it illustrates a kind of another kind of structural representation determining the system of the depth of water that the embodiment of the present invention provides, on the basis of Fig. 3, can also comprise: first estimates unit 17, second estimates unit 18 and the 3rd and estimate unit 19.Wherein:

First estimates unit 17, and the time span for measuring according to surveying instrument is far smaller than the time scale relation of density of sea water change, obtains the first discreet value of described third value according to the following equation:

$\begin{array}{c}\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)\&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}\\ \&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}(\mathrm{\&rho;}(t_0,h\left(t_0\right))+\mathrm{\&Delta;\&rho;}(t,z))(g\left(h\left(t_0\right)\right)+\mathrm{\&Delta;g}\left(z\right))\mathrm{dz}\\ \&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}(\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)+\mathrm{\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(z\right)+\mathrm{\&Delta;\&rho;}(t,z)g\left(h\left(t_0\right)\right)+\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right))\mathrm{dz}\\ \&ap;\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right)\\ +{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}+{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)g\left(h\left(t_0\right)\right)\mathrm{dz}\\ +{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}\end{array}$

Wherein, the function that △ g (z) is the depth of water, △ ρ (t, z) is ocean temperature, the function of salinity and density.

Because marine bottom ocean current is more weak, marine stream slowly, therefore can think that sitting bottom pressure sensor remains on a fixing depth of water.When the time span that surveying instrument is measured is far smaller than the time scale of density of sea water change, can estimates in unit first and third value be estimated, to obtain the first discreet value of third value.

Second estimates unit 18, for according to described perpendicular displacement △ h (t) scope and described △ g (z) and △ ρ (t, z) variation relation, and the first discreet value of described third value, obtain described second discreet value according to the following equation:

$\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)\&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}\&ap;\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right).$

3rd estimates unit 19, for determining the discreet value of described perpendicular displacement.

In addition the 3rd estimate unit and can also adopt structural representation as shown in Figure 5, can comprise: the 5th computing unit 231, the 6th computing unit 232 and the 4th determining unit 233.Wherein:

First computing unit 231, for determining the inverse of the expression formula multiplied result of density of sea water and acceleration of gravity.

Second computing unit 232, for carrying out first order Taylor expansion by numerical value reciprocal.

Utilize Taylor expansion formula to launch the formula calculated in the first computing unit 231, and first approximation is carried out to it, obtain the 3rd discreet value according to first approximation.

4th determining unit 233, the discreet value of described perpendicular displacement is determined according to described 3rd discreet value and following formula:

$\mathrm{\&Delta;h}\left(t\right)\&ap;\frac{\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)}{{\mathrm{\&rho;}}_0{g}_0}.$

The system of the determination depth of water that the embodiment of the present invention provides, utilizes linear perturbation theory to carry out theory deduction, predictor error, directly obtains the depth of water relative to mean sea level, reduces environmental factor to the impact calculated.The error that wherein the initial depth of water causes is an offset error, can not change in computation process along with the change of time.When the initial depth of water gives timing, the density of sea water that the error of above method is mainly derived from surveying instrument displacement in the vertical direction and causes and the change that gravity accelerates, can not more than 4% according to the error of the known perpendicular displacement of above-mentioned theoretical analysis, and this error does not change over time.

Finally, also it should be noted that, in this article, the such as relational terms of first and second grades and so on is only used for an entity or operation to separate with another entity or operational zone, and not necessarily requires or imply the relation that there is any this reality between these entities or operation or sequentially.And, term " comprises ", " comprising " or its any other variant are intended to contain comprising of nonexcludability, thus make to comprise the process of a series of key element, method, article or equipment and not only comprise those key elements, but also comprise other key elements clearly do not listed, or also comprise by the intrinsic key element of this process, method, article or equipment.When not more restrictions, the key element limited by statement " comprising ... ", and be not precluded within process, method, article or the equipment comprising described key element and also there is other identical element.

To the above-mentioned explanation of the disclosed embodiments, those skilled in the art are realized or uses the present invention.To be apparent for a person skilled in the art to the multiple amendment of these embodiments, General Principle as defined herein can without departing from the spirit or scope of the present invention, realize in other embodiments.Therefore, the present invention can not be restricted to these embodiments shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.

Claims (10)

1. determine a method for the depth of water, it is characterized in that, described method comprises:

Obtain the initial depth of water;

Obtain extra large the second pressure sum that the above unit area seawater of atmospheric pressure and seabed causes and the surveying instrument shown of the first pressure sum that initial time sea table atmospheric pressure and seabed above unit area seawater cause, the original pressure of surveying instrument in described initial water depths, end time respectively in the termination pressure stopping depth of water place;

Determine the difference of described first pressure sum and described original pressure respectively, obtain the first numerical value, the difference of described second pressure sum and described termination pressure, obtain second value;

Determine the difference of described second value and described first numerical value, obtain third value;

Determine the ratio of described third value and the reference density of sea water transferred and acceleration of gravity parameter multiplied result, obtain perpendicular displacement;

Determine the difference of the described initial depth of water and described perpendicular displacement, obtain the depth of water at described termination depth of water place.

2. method according to claim 1, is characterized in that, determines the difference of described second value and described first numerical value, obtains described third value according to the following equation:

$\begin{array}{c}\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)=({\&Integral;}_{-D\left(t\right)}^{-h\left(t_0\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}-{\&Integral;}_{-D\left(t_0\right)}^{-h\left(t_0\right)}\mathrm{\&rho;}(t_0,z)g\left(z\right)\mathrm{dz})\\ +{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}\end{array}$

Wherein ,-D (t) is the depth of water, and ρ (t, z) is density of sea water, and g (z) is acceleration of gravity.

3. method according to claim 2, is characterized in that, is far smaller than a layer time scale relation for density of sea water change, obtains the first discreet value of described third value according to the following equation according to the time span that surveying instrument is measured:

$\begin{array}{c}\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)\&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}\\ \&ap;\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right)\\ +{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}+{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(h\left(t_0\right)\right)\mathrm{dz}\\ +{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}\end{array}$

Wherein, the function that △ g (z) is the depth of water, △ ρ (t, z) is ocean temperature, the function of salinity and density.

4. method according to claim 3, it is characterized in that, according to described perpendicular displacement △ h (t) scope and described △ g (z) and △ ρ (t, z) variation relation, and the first discreet value of described third value, obtain described second discreet value according to the following equation:

$\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)\&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}\&ap;\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right).$

5. method according to claim 4, is characterized in that, obtains described perpendicular displacement according to described second discreet value and following formula:

$\mathrm{\&Delta;h}\left(t\right)\&ap;\frac{\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)}{\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}.$

6. method according to claim 5, is characterized in that, comprises after obtaining described perpendicular displacement:

Obtain the 3rd discreet value, described 3rd discreet value is for determining the discreet value of described perpendicular displacement.

7. method according to claim 6, is characterized in that, described 3rd discreet value of described acquisition comprises:

Determine one with the ratio of the expression formula multiplied result of described density of sea water and described acceleration of gravity;

Described reciprocal value is carried out first order Taylor expansion, obtains the 3rd discreet value of described inverse according to the following equation:

$\begin{array}{c}\frac{1}{\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}=\frac{1}{({\mathrm{\&rho;}}_0+\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right)))(g_0+\mathrm{\&Delta;g}\left(h\left(t_0\right)\right))}\\ \&ap;(\frac{1}{{\mathrm{\&rho;}}_0}-\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))}{{{\mathrm{\&rho;}}_0}^2}+O\left(\mathrm{\&Delta;}{\mathrm{\&rho;}}^2(t_0,h\left(t_0\right))\right))\&times;(\frac{1}{g_0}-\frac{\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{g_0}^2}+O\left(\mathrm{\&Delta;}{g}^2\left(h\left(t_0\right)\right)\right))\\ \&ap;(\frac{1}{{\mathrm{\&rho;}}_0{g}_0}-\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))}{{{\mathrm{\&rho;}}_0}^2{g}_0}-\frac{\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{\mathrm{\&rho;}}_0{g_0}^2}+\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{{\mathrm{\&rho;}}_0}^2{g_0}^2})\\ +O(\mathrm{\&Delta;}{\mathrm{\&rho;}}^2(t_0,h\left(t_0\right)),\mathrm{\&Delta;}{g}^2\left(h\left(t_0\right)\right))\\ \&ap;\frac{1}{{\mathrm{\&rho;}}_0{g}_0}\end{array}.\stackrel{}{}$

8. determine a system for the depth of water, it is characterized in that, described system comprises:

First acquiring unit, for obtaining the initial depth of water;

Second acquisition unit, for obtaining extra large the second pressure sum that the above unit area seawater of atmospheric pressure and seabed causes and the surveying instrument shown of the first pressure sum that initial time sea table atmospheric pressure and seabed above unit area seawater cause, the original pressure of surveying instrument in described initial water depths, end time respectively in the termination pressure stopping depth of water place;

First determining unit, for determining the difference of described first pressure sum and described original pressure respectively, obtains the first numerical value, determines the difference of described second pressure sum and described termination pressure, obtains second value;

Second determining unit, for determining the difference of described second value and described first numerical value, obtains third value;

4th acquiring unit, for determining the ratio of described third value and the reference density of sea water transferred and acceleration of gravity parameter multiplied result, obtains perpendicular displacement;

3rd determining unit, for determining the difference of the described initial depth of water and described perpendicular displacement, obtains the depth of water at described termination depth of water place.

9. system according to claim 8, is characterized in that, described system also comprises:

First estimates unit, is far smaller than the time scale relation of density of sea water change, obtains the first discreet value of described third value according to the following equation according to the time span of surveying instrument measurement:

$\begin{array}{c}\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)\&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}\\ \&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}(\mathrm{\&rho;}(t_0,h\left(t_0\right))+\mathrm{\&Delta;\&rho;}(t,z))(g\left(h\left(t_0\right)\right)+\mathrm{\&Delta;g}\left(z\right))\mathrm{dz}\\ \&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}(\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)+\mathrm{\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(z\right)+\mathrm{\&Delta;\&rho;}(t,z)g\left(h\left(t_0\right)\right)+\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right))\mathrm{dz}\\ \&ap;\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right)\\ +{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}+{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)g\left(h\left(t_0\right)\right)\mathrm{dz}\\ +{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&Delta;\&rho;}(t,z)\mathrm{\&Delta;g}\left(z\right)\mathrm{dz}\end{array}$

Wherein, the function that △ g (z) is the depth of water, the function of △ ρ (t, z) position ocean temperature, salinity and density;

Second estimates unit, for according to described perpendicular displacement △ h (t) scope and described △ g (z) and △ ρ (t, z) variation relation, and the first discreet value of described third value, obtain described second discreet value according to the following equation:

$\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)\&ap;{\&Integral;}_{-h\left(t_0\right)}^{-h\left(t_0\right)+\mathrm{\&Delta;h}\left(t\right)}\mathrm{\&rho;}(t,z)g\left(z\right)\mathrm{dz}\&ap;\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)\mathrm{\&Delta;h}\left(t\right);$

3rd estimates unit, for determining the discreet value of described perpendicular displacement.

10. system according to claim 9, is characterized in that, the described 3rd estimates unit comprises:

First computing unit, for determining the inverse of the expression formula multiplied result of density of sea water and acceleration of gravity;

Second computing unit, for described reciprocal value is carried out first order Taylor expansion, obtains the 3rd discreet value of described inverse according to the following equation:

$\begin{array}{c}\frac{1}{\mathrm{\&rho;}(t_0,h\left(t_0\right))g\left(h\left(t_0\right)\right)}=\frac{1}{({\mathrm{\&rho;}}_0+\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right)))(g_0+\mathrm{\&Delta;g}\left(h\left(t_0\right)\right))}\\ \&ap;(\frac{1}{{\mathrm{\&rho;}}_0}-\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))}{{{\mathrm{\&rho;}}_0}^2}+O\left(\mathrm{\&Delta;}{\mathrm{\&rho;}}^2(t_0,h\left(t_0\right))\right))\&times;(\frac{1}{g_0}-\frac{\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{g_0}^2}+O\left(\mathrm{\&Delta;}{g}^2\left(h\left(t_0\right)\right)\right))\\ \&ap;(\frac{1}{{\mathrm{\&rho;}}_0{g}_0}-\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))}{{{\mathrm{\&rho;}}_0}^2{g}_0}-\frac{\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{\mathrm{\&rho;}}_0{g_0}^2}+\frac{\mathrm{\&Delta;\&rho;}(t_0,h\left(t_0\right))\mathrm{\&Delta;g}\left(h\left(t_0\right)\right)}{{{\mathrm{\&rho;}}_0}^2{g_0}^2})\\ +O(\mathrm{\&Delta;}{\mathrm{\&rho;}}^2(t_0,h\left(t_0\right)),\mathrm{\&Delta;}{g}^2\left(h\left(t_0\right)\right))\\ \&ap;\frac{1}{{\mathrm{\&rho;}}_0{g}_0}\end{array};$

4th determining unit, the discreet value of described perpendicular displacement is determined according to described 3rd discreet value and following formula:

$\mathrm{\&Delta;h}\left(t\right)\&ap;\frac{\mathrm{\&Delta;P}\left(t\right)-\mathrm{\&Delta;P}\left(t_0\right)}{{\mathrm{\&rho;}}_0{g}_0}.$