Dynamic tolerance setup method based on scan line arithmetic

Abstract

The invention provides a scanning line algorithm, comprising calculating an absolute error of an intersection point coordinate based on a formula for calculating tolerance and a process for calculating a line segment intersection point; calculating a tolerance of whether a judging point is on the line segment or not, based on the formula for calculating tolerance, the absolute error of the intersection point coordinate and the calculating process for determining whether the point is on the line segment or not; determining whether the point is on the line segment or not. The invention can determine the tolerance after floating point number operating, further, under the precondition that the operation of floating point values representing the point coordinate and the line segment and so on exists the error, rightly judging whether the event point is on the line segment or not, thereby ensuring the correctness of the scanning line algorithm.

Description

technical field [0001] The invention relates to a scanning line algorithm applied in a geographic information system, in particular to a dynamic tolerance setting method based on the scanning line algorithm. Background technique [0002] Geographic Information System (GIS) is a specific and very important spatial information system. It is a technical system that collects, stores, manages, calculates, analyzes, displays and describes the relevant geographical distribution data in the entire or part of the earth's surface (including the atmosphere) space with the support of computer hardware and software systems. The core of geographic information system is to process spatial geographic data, including point-surface overlay, line-surface overlay and area-surface overlay. All overlay analysis is based on the processing of associated line segment clusters and line segment intersections. [0003] The scanline algorithm is a classic algorithm that outputs the intersection points ...

AI Technical Summary

Problems solved by technology

However, the scanning line algorithm cannot avoid the existence of errors in practical applications; and when it is applied in geographic information systems, it may encounter geographical data of different coordinate systems, and the numerical ranges of these data are very different, for example: in units of latitude and longitude If the value is less than 1000; when the unit is kilometers, the value may be tens of thousands; when the unit is meters, the value may be millions

Therefore, the static setting tolerance cannot guarantee the correctness of the scan line algorithm in judging whether the event point is on the line segment

Images