CN108647692A - Ocean stratification extractive technique based on LH histograms - Google Patents
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Abstract
The present invention relates to a kind of Ocean stratification extractive techniques based on thermohaline data.Studies have found that ocean has layer knot（Ocean stratification refers to hierarchical structure of the thermodynamic state parameters such as the density, temperature, salinity of seawater with depth distribution）, there is currently direct volume drawing visualization technique it is more difficult to the extraction of this Ocean stratification, therefore we effectively extract Ocean stratification during the direct volume drawing of ocean using the technologies such as LH histograms and Region Grow.LH histograms are one kind of two-dimensional histogram, and transverse and longitudinal coordinate axis indicates L (lower), H (higher) value respectively.The technology is first handled ocean thermohaline data, calculates Lower the and Higher values of each voxel, generates LH two-dimensional histograms；Then, Ocean stratification is chosen on the LH histograms of generation；Finally, direct volume drawing is carried out according to selected result.If the LH histograms generated do not distinguish layer knot effectively, a seed point can be chosen on the histogram of generation, and selected voxel is clustered under given criterion using Region Grow technologies, direct volume drawing is carried out after being disposed.
Description
Technical field
The invention belongs to marine information technical fields, and in particular to the Ocean stratification extractive technique based on LH histograms.
Background technology
Since the Ocean stratification discovery of 19th century, it is always the important content of physical oceangraphy research.Ocean stratification can
To be divided into epilimnion, pycnocline, halocline, transition layer of sound velozity etc., there are achievement in research higher academic and military affairs to answer
With value.For example, pycnocline is very big on the military activities such as submarine activity, anti-submarine warfare influence, it is larger when occurring in ocean
Positive density gradient, i.e., " liquid seabed ", submarine can rest on the interface of spring layer, keep it is noiseless standby, can be effectively
Evade the detection search of sonar.With " liquid seabed " on the contrary, if upper ocean water density is big, lower layer's density of sea water is small, as close
The inverse spring layer of degree, will form " the marine cliff of displacement ".When submarine encounters " the marine cliff of displacement ", since the buoyancy that submarine is subject to subtracts suddenly
Small, if taking measures to mitigate submarine weight not in time, submarine will rapidly sink suddenly, cause major accident.Just because of this,
Naval of various countries all attaches great importance to the research of pycnocline.
Therefore, data visualization is turned to intuitive, the effective data research means of one kind and method, it studies thalassographer
Oceanographic phenomena has great importance.Early stage people study sea in such a way that oceanographic data draws the deep line chart of temperature, close deep line chart etc.
The layer knot in ocean.Later with the fast development of visualization technique, Volume Rendering Techniques are employed for oceanography field.
Volume Rendering Techniques are divided into many kinds, and data object plotting method common at present has light quantum mechanics, snow throwing ball, base
In the 3D textures mappings etc. of hardware.
(1) light quantum mechanics:Light quantum mechanics are a kind of using pattern space as the object plotting method of sequence, it is from pattern space
Each pixel set out, by direction of visual lines emit a ray, this ray pass through 3 d data field, along this ray select
K equidistant sampled points, and cubic curve is made by the color value and opacity value of 8 data points nearest apart from a certain sampled point
Property interpolation, finds out the opacity value and color value of the sampled point.Again by the color value of each sampled point on every ray and impermeable
Brightness value is synthesized from the front to the back or from the front to the back, you can obtain sending out the color value at the picture element of the ray, so as to
To obtain final image on the screen.
(2) snow throwing ball：Different from light quantum mechanics, Splatting is to carry out operation to voxel repeatedly.It is with one
Referred to as footprint（Footprint ）Function calculate the coverage of each voxel projection, define intensity distribution with Gaussian function
（Center intensity is big, and edged intensity is small）, to calculate its overall contribution to image, and synthesized, form last figure
As.
(3) hardware based 3D textures mappings:The speed of drafting is all the main problem of volume drawing all the time, because
For the image of generation, the processing in each region of object can influence its quality, it is therefore desirable to each voxel is calculated,
And after voxelization, repositions voxel and need sizable calculation amount again.In order to solve the problems, such as volume drawing speed, people
Propose many modified hydrothermal process, these algorithms what is common is that improving the efficiency of drafting on the basis of software, as above
The algorithm that face is introduced.And throe-dimensional temperature method is to improve the speed of volume drawing based on hardware.
Ocean stratification is visually studied currently with Volume Rendering Techniques fewer, and is using by attribute value mostly
The displaying of the joint histogram progress data characteristics constituted with attribute gradient values, however the different material in two-dimentional joint histogram
Boundary between will produce overlapping, cannot to boundary carry out effectively divide and extract.
Invention content
The technique effect of the present invention can overcome drawbacks described above, provide a kind of Ocean stratification extraction skill based on LH histograms
Art.LH histograms are one kind of two-dimensional histogram, and transverse and longitudinal coordinate axis corresponds to L (lower), H (higher) value respectively；L, H values
Indicate the property value of the relatively low and higher category of composition material boundary.Direct volume drawing is being carried out to ocean using two-dimentional joint histogram
In the process, the boundary between the layer knot information of ocean not apparent enough and different material shown in joint histogram there is
Overlapping.We will effectively divide Ocean stratification using LH histograms, and different material boundary is avoided to generate the feelings of overlapping
Condition.And Ocean stratification can be clustered using Region Gorw technologies in the case where LH histogram effects are undesirable
It draws.
To achieve the above object, the present invention adopts the following technical scheme that, the specific steps are (be with the cross-sectional data of Argo
Example)：
（1）Give an epsilon（Epsilon is the number more than 0）Threshold value；
（2）Start to calculate adjacent 2 points of temperature gradient amplitude with first data point of first section along depth direction
grad;
（3）Judge calculate i-th（I is since 1）The grad of a data point and the magnitude relationship of given threshold value, and according to comparing
As a result the FL of the data point, FH values are set；
（4）Continue the comparison and the assignment operation that calculate the temperature gradient of i+1 point and execute the 3rd step, until meeting centainly
Condition then stops, and a section processing finishes；
（5）Repeat（4）Step, until being disposed, all sections then stop；
（6）The FH of all data points, FL are counted and draw LH histograms；
（7）Region Grow technologies are utilized on the basis of the LH histograms drawn, and all voxels are clustered；
（8）In render process, the opacity of voxel is set using the gradient magnitude of each data point, is made near proximal border
Voxel（Gradient is maximum）It is strengthened.
The beneficial effects of the present invention are：Utilize the advantage that different material boundary can be avoided overlapped of LH histograms
Ocean stratification effectively divide and extract, the hierarchical structures such as ocean mixed layer, spring layer are individually visualized, are carried
More horn of plenty, intuitive visual experience are supplied.It is not to manage very much in the effect of LH histograms in addition combined with Region Grow technologies
Different material can be clustered in the case of thinking, to carry out effective division of material boundary.
Description of the drawings
Ocean stratification extractive technique flow charts of the Fig. 1 based on LH histograms.
Specific implementation mode
The Ocean stratification extractive technique based on LH histograms of the present invention（As shown in Figure 1）, include the following steps (with cuing open for Argo
For face data)：
（1）Give an epsilon（Epsilon is the number more than 0）Threshold value；
（2）Start to calculate adjacent 2 points of temperature gradient amplitude with first data point of first section along depth direction
Grad, and using the gradient magnitude as the Grad of the mean depth of two depth corresponding with this two temperature;
（3）Judge calculate i-th（I is since 1）The grad of a data point and the magnitude relationship of given threshold value：
1. working as grad<When=epsilon, then it represents that the point is located in homogeneous substance, enables FL (i)（Lower values） = FH(i)
（Higher values）The intensity value of=the data point, and record the FH of the point；
2. working as grad>When epsilon, then it represents that the point is located on boundary, and the FH (i) of the point is enabled to be remembered equal to (i-1)-th point
The FH values of record；
（4）Continue the comparison and the assignment operation that calculate the temperature gradient of i+1 point and execute the 3rd step, until working as again
J-th point of grad<=epsilon, enables FH (j)=FL (j)=intensity value of the point, and enables all FL calculated above
FL=FL (j) of unassignable point；
（5）Repeat（4）Step, until being disposed, all sections then stop；
（6）According to the FH of all data points, FL values will have identical FH, the point of FL values to carry out cumulative statistics；
（7）According to（6）Statistical result draw two dimension LH histograms；
（8）The seed point a little as Region Grow is selected on the material boundary for the LH histograms drawn, in LH histograms
Figure center selects certain range, then calculates the cost risen to from seed point needed for selected point according to given rule
Value；
（9）According to（8）Whether the cost values of middle calculating judge selected point on the boundary where seed point；
（10）In render process, the opacity of voxel is set using the gradient magnitude of each data point, is made near proximal border
Voxel（Gradient is maximum）It is strengthened.
Claims (9)
1. the Ocean stratification extracting method based on LH histograms, specifically includes following basic step：
(1) epsilon is given（Epsilon is the number more than 0）Threshold value, it is characterised in that：Artificially give an epsilon
Threshold value, as the fiducial value for judging Ocean stratification；
(2) adjacent along depth direction calculating since first data point of first section by taking Argo cross-sectional datas as an example
2 points of temperature gradient amplitude grad, it is characterised in that：Along between two data points of vertical depth direction calculating of section
Temperature gradient amplitude grad, and using the gradient magnitude as the ladder of the mean depth of two depth corresponding with this two temperature
Angle value；
(3) judge calculate i-th（I is since 1）The grad of a data point with（1）The magnitude relationship of middle given threshold value, and according to
The FL of the data point, FH values is arranged in result of the comparison, it is characterised in that：By the gradient magnitude result of calculating with（1）Given
Epsilon values are compared, and then think that the data point is located at the extra large layer of thermohaline uniform properties when gradient magnitude is less than epsilon
In, otherwise it is located among the larger spring layer of thermohaline change of properties；
(4) continue to calculate temperature gradient and the execution the of i+1 point（3）The comparison of step and assignment operation, until a section
It is disposed, it is characterised in that：According to（3）All data points of step one section of processing, and generate corresponding LH data values；
(5) is repeated（4）Step, until being disposed, all sections then stop, it is characterised in that：Repeat different sections
On all data points calculating, compare and amplitude operation；
(6) FH of all data points, FL are counted and draw LH histograms, it is characterised in that：To（5）Walk the LH generated
Data are counted, and the number for the data point for including in each pixel in LH coordinate systems is counted, and are then utilized in statistical data
Maximum value carry out the normalization of all data, LH grey level histograms are finally drawn according to the result after normalization；
(7) Region Grow technologies are utilized on the basis of the LH histograms drawn, and all voxels are clustered, it is special
Sign is：In the case where LH histograms cannot well distinguish Ocean stratification, Region is used in LH spatial domains
Grow technologies carry out cluster operation；
(8) in render process, the opacity of voxel is set using the gradient magnitude of each data point, is made near proximal border
Voxel（Gradient is maximum）It is strengthened, it is characterised in that：During last data render, provicial commander's size of data point is utilized
Different lightness are set, and the opacity that the larger data point of gradient is arranged is larger.
2. the Ocean stratification extracting method according to claim 1 based on LH histograms, which is characterized in that the step
（1）In, threshold value epsilon is the number more than 0, and under normal circumstances, when Hai Shen is less than 200 meters, epsilon values are 0.2, when
Value is 0.05 when Hai Shen is more than 200 meters.
3. the Ocean stratification extracting method according to claim 1 based on LH histograms, which is characterized in that the step
（2）In, the gradient magnitude computational methods of data point are that the temperature value of lower data point subtracts the temperature value of upper layer data point, gained
Difference divided by lower data point depth value and upper layer data point depth value difference, the result of last gained takes absolute value
It is just the gradient magnitude of the data point.
4. the Ocean stratification extracting method according to claim 1 based on LH histograms, which is characterized in that the step
（3）In, judge calculate i-th（I is since 1）The grad of a data point with（1）The magnitude relationship of middle given threshold value：
1. working as grad<When=epsilon, then it represents that the point is located in homogeneous substance, enables FL (i)（Lower values） = FH(i)
（Higher values）The intensity value of=the data point, and record the FH of the point；
2. working as grad>When epsilon, then it represents that the point is located on boundary, and the FH (i) of the point is enabled to be remembered equal to (i-1)-th point
The FH values of record.
5. the Ocean stratification extracting method according to claim 1 based on LH histograms, which is characterized in that the step
（4）In, continue the temperature gradient for calculating i+1 point and execution the（3）The comparison of step and assignment operation, until working as again
J-th point of grad<=epsilon, enables FH (j)=FL (j)=intensity value of the point, and enables all FL calculated above
FL=FL (j) of unassignable point.
6. the Ocean stratification extracting method according to claim 1 based on LH histograms, which is characterized in that the step
（5）In, it repeats the calculating of all data points on different sections, compare and amplitude operation.
7. the Ocean stratification extracting method according to claim 1 based on LH histograms, which is characterized in that the step
（6）In, horizontal axis is L values in LH histograms, and vertical reference axis is H values.
8. the Ocean stratification extracting method according to claim 1 based on LH histograms, which is characterized in that the step
（7）In, the seed point a little as Region Grow is selected on the material boundary for the LH histograms drawn, in LH histograms
Figure center selects certain range, then calculates the cost risen to from seed point needed for selected point according to given rule
Value.
9. the Ocean stratification extracting method according to claim 1 based on LH histograms, which is characterized in that the step
（8）In, in last render process, using each data point gradient magnitude be arranged voxel opacity, make near
The voxel on boundary（Gradient is maximum）Different lightness it is larger, the boundary of last result between different layers knot is strengthened.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN118688875A (en) * | 2024-08-26 | 2024-09-24 | 自然资源部第一海洋研究所 | Simulation diagnosis method and system for ocean density gradient zone and underwater cliff |
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Address after: No. 238 Songling Road, Laoshan District, Qingdao City, Shandong Province Patentee after: OCEAN University OF CHINA Country or region after: China Patentee after: Qingdao Marine Science and Technology Center Address before: 266100 Shandong Province, Qingdao city Laoshan District Songling Road No. 238 Patentee before: OCEAN University OF CHINA Country or region before: China Patentee before: QINGDAO NATIONAL LABORATORY FOR MARINE SCIENCE AND TECHNOLOGY DEVELOPMENT CENTER |