Point group (data form)
A point group (てんぐん) and the point cloud (British: point cloud) are the sets of the point to treat with a computer. In many cases, it is three dimensions, and the space is often expressed in an X-Y coordinate system (x, y, z).
Table of contents
Summary
The point group can make even the three-dimensional scanner with the laser. The three-dimensional scanner measures the object surface automatically and outputs the three-dimensional coordinate of a large number of points in a data file as a point group. As a general rule, the data express a position, the shape of the object surface to use the reflection by the object of the laser and do not express the situation in the object.
There are the three-dimensional CAD model making of parts, the quality control by the measurement, visualization processing, an animation, rendering, mass customization in the application field of the point group.
The point group can just perform rendering, but is not often suitable for various three-dimensional processing as the data form. Therefore I convert data into a mask type and often treat it as a polygon, mesh of the irregular triangulation, the non-same Yuri B spline (NURBS) curved surface, a CAD model. I convert it into ドロネー triangulation, technique to generate an aspect from the position of the existing point including the alpha shape method and the point group three dimensions distance ground (British: volumetric distance field), and, in conversion technique, there is technique to convert into the surface (British: implicit surface) of the shade.
Applied
There is industrial inspection in the application field of the point group. I compare the differences between point group data and CAD model in the design of made parts and inspect it. I can display the difference of both for a difference of the colors visually. I can measure size and the clearance from the point group, too.
The three-dimensional data obtained from the point group are used for medical imaging processing. The reduction of data is possible by using a point group.
In the geographical information system (GIS), I can make a numerical value altitude model (DEM) of the ground from a point group.
Various data form
Absolute coordinate
For the measurement with the laser, former data of the point group are measuring equipment and relative distance between the objects. When I express the position of products of the district in a geographical information system, I measure an absolute coordinate (latitude, longitude, altitude) of the measuring equipment by GPS and may display this coordinate at the absolute coordinate which I added. At this chance I add the point group acquisition time with the GPS and express data form at (latitude, longitude, altitude, the time).
Coloring of the point
I express the surface color of the object at RGB coordinate and may express data form like (for latitude, longitude, altitude, time, R (red ingredient), G (green ingredient), B (Kiyoshige)). To this end, I point a camera to the direction of radiation of the laser and take the color data of the considerable position of the provided image [1].
Allied item
References
This article is taken from the Japanese Wikipedia Point group (data form)
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