Precision improving device for three dimensional topographical data, precision improving method for three dimensional topographical data and recording medium

A three-dimensional topographical data precision improving method removing noise that occurs in water regions of three-dimensional topographical data as a result of stereo matching errors upon three-dimensional information calculation in three-dimensional topographical data established from stereoscopic photographs, comprising:

• a determination step of determining whether there are any water regions in the input three-dimensional topographical data;
• a water region specifying step of specifying the range of any one water region;
• a feature extraction step of extracting feature values on each point in the three-dimensional topographical data based on altitude distribution pattern in the local region of the each point, and extracting feature values within the specified one water region;
• a segmentation step of segmenting the points in the three-dimensional topographical data into candidate water regions and non-water regions by using the extracted feature values within the specified water region as a water region determination reference value, comparing the feature values of each point in the three-dimensional topographical data with the water region determination reference value, and determining that the point belongs to the candidate water region if the difference is equal to or smaller than a given threshold, and otherwise determining that the point belongs to the non-water region;
• a water region extraction step of extracting a connected component having the same or wider area than a given threshold among the candidate water regions as a water region based on the results in the segmentation step;
• and
• a plane creation step of creating a corrected plane joined to the boundary of each water region extracted in the water region extraction step using the altitudes of the surrounding non-water regions adjoining to the water region extracted in the water region extraction step, and replacing the water region extracted in the water region extraction step with the corrected plane.

A non-transitory computer-readable recording medium on which a program is recorded according to a third exemplary aspect of the present invention records a program allowing a computer removing noise that occurs in water regions of three-dimensional topographical data as a result of stereo matching errors upon three-dimensional information calculation in three-dimensional topographical data established from stereoscopic photographs to function as:

• a determination unit determining whether there are any water regions in the input three-dimensional topographical data;
• a water region specifying unit specifying the range of any one water region;
• a feature extraction unit extracting feature values on each point in the three-dimensional topographical data based on altitude distribution pattern in the local region of the each point, and extracting feature values within the specified one water region;
• a segmentation unit segmenting the points in the three-dimensional topographical data into candidate water regions and non-water regions by using the extracted feature values within the specified water region as a water region determination reference value, comparing the feature values of each point in the three-dimensional topographical data with the water region determination reference value, and determining that the point belongs to the candidate water region if the difference is equal to or smaller than a given threshold, and otherwise determining that the point belongs to the non-water region;
• a water region extraction unit extracting a connected component having the same or wider area than a given threshold among the candidate water regions as a water region based on the results of the segmentation unit;
• and
• a plane creation unit creating a corrected plane joined to the boundary of each water region extracted by the water region extraction unit using the altitudes of the surrounding non-water regions adjoining to the water region extracted by the water region extraction unit, and replacing the water region extracted by the water region extraction unit with the corrected plane.