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A Method for Evaluating the Smoothness of Contour Lines on Nautical Charts

A technology of isobath and smoothness, applied in image analysis, image data processing, instruments, etc., can solve problems such as evaluating the smoothness of isobath of nautical charts

Active Publication Date: 2021-10-19
PLA DALIAN NAVAL ACADEMY
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

After deleting the small and curved isobaths, whether its expression on the chart can meet the requirements of the clarity of the chart, and whether the isobaths trend is smooth or not, currently mainly depends on the qualitative analysis of chart charters through manual visual interpretation. However, there is no published literature that can quantitatively evaluate the smoothness of isobaths in nautical charts

Method used

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  • A Method for Evaluating the Smoothness of Contour Lines on Nautical Charts
  • A Method for Evaluating the Smoothness of Contour Lines on Nautical Charts
  • A Method for Evaluating the Smoothness of Contour Lines on Nautical Charts

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Embodiment Construction

[0039] The method for evaluating the smoothness of the isobaths of the nautical charts of the present invention uses a computer to realize the evaluation of the smoothness of the isobaths of the nautical charts. Suppose a certain isobath line l on the nautical chart, adopt the method of the present invention to evaluate the smoothness of the isobath line of the nautical chart, comprising the following steps, as Figure 4 Shown:

[0040] Step a, read all nodes p on the isobath line l on the chart 1 ,p 2 ,...,p n The plane position of (x i ,y i )(i=1,2,Λ,n);

[0041] Step b, extract the first node p from the isobath line l 1 , denoted as the current node p i ;

[0042] Step c, judge whether the current node is the first (or last) node on the isobath, if yes, go to step d; otherwise, extract the previous and next nodes of the current node on the isobath, and record it as the previous node p i-1 , back node p i+1 , go to step f;

[0043] Step d, judging whether the iso...

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Abstract

A method for evaluating the smoothness of isobaths on a nautical chart, comprising the following steps: sequentially reading the plane positions of all nodes on a certain isobath on the nautical chart; The line segment connecting the node and the back node is the back line segment, and the line segment connecting the front node and the back node is the anti-line segment; calculate the curvature of the isobath at the current node; calculate the smooth deviation of the isobath at the current node; calculate the front line The chord distance from the segment and the back line segment to the circumcircle; calculate the mean value of curvature of the isobath at all nodes, the maximum value of the smooth dispersion, and the maximum value of the chord distance. The method for evaluating the smoothness of the isobath of the navigation chart of the present invention realizes the evaluation of the smoothness of the isobath by a computer, thereby being able to more accurately reflect the navigability of the waterway, reasonably display the seabed topography, etc., and improve navigation safety.

Description

technical field [0001] The invention relates to the technical field of marine surveying and mapping, in particular to a method for evaluating contours of nautical charts. Background technique [0002] Isobath refers to a smooth curve connecting adjacent points of equal seabed depth calculated from the theoretical depth datum, that is, a closed curve passing through points of the same water depth. On nautical charts, isobaths play a very important role in ensuring navigation safety, accurately reflecting the navigability of waterways, and reasonably displaying seabed landforms. [0003] The isobath line representation of nautical charts first needs to ensure the safety of the ship’s maritime navigation, and secondly, it must express the navigable resources as fully as possible. In addition, in the process of synthesizing the isobaths of the nautical chart, in order to maintain the clarity of the drawing, it is necessary to delete the small bends on the isobaths. After delet...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06F16/29G06T7/00G06T7/60
CPCG06T7/0002G06T7/60
Inventor 贾帅东张立华
Owner PLA DALIAN NAVAL ACADEMY
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