The procedure of our algorithm is as follows:
- Checking four control points used by pre-matching on each map. If the coordinates still have some differences on cadastral map, we move them to the related points on road map. Then fix all these points (it means that these points will be no change in following transforms).
- Automatically searching one similar feature point one each map based on the given distance parameter and point sequence. If one feature point has been found, we select three control points within four given points at beginning. The rule for selecting three control points is based on the maximum area generated by final four points.
- Affine transforming the cadastral map by using the selected four points. Checking the coordinator differences between two maps. If the contribution (the coordinator differences) of this step processing is too big, the pre-result will be no modifying. Otherwise, changing the pre-result with new coordinates.
- If the coordinator differences between the automatically searched feature point and its related points on road map in smaller than given limited, moving and fixing two points.
- Sequentially processing the step 2-4 until the end.
The algorithm has three good points. First is simple by using Affine transform only. But the sequential simple processing will approach the complicated result. Second is easy to control because we only select one new point for processing. Third is high reliability since these three points are selected by operators and they have high accuracy and good distribution.
Boundary Line based Automated Adjustment
The algorithm for automated adjusting cadastral lines based on given boundary lines includes following three parts:
- Searching the conflicted cadastral lines based on given boundary lines;
- Moving the conflicted cadastral lines to given boundary lines;
- Related cadastral line adjustment.
- Searching the conflicted cadastral lines
We use three parameters (distance between two lines, angle between two lines, and distance between end points) to search the conflicted cadastral lines. That means we only want to modify the cadastral line, which is almost parallel to one of boundary line and has limited distance between two lines and one of end point. The distance between two lines can be calculated by averaging the two distances from end points to lines.
- Moving the conflicted cadastral lines
If one cadastral line has been checked as a conflicted line by above three parameters, we move it to the given boundary line based on the end point which has minimum distance between two lines. We sequentially move all conflicting cadastral lines until the end.
- Related cadastral line adjustment
The processing includes following four parts:
- Searching the related cadastral lines based on the end pints;
- Moving each one of end pint on the conflicted cadastral lines to new points;
- Adjusting each another end point on the modified lines checked by the direction changing between new and old lines.
- Sequentially doing above processing until the end.
Building Line based Automated Adjustment
The algorithm for automated adjusting cadastral lines based on given building lines includes following three parts:
- Searching the conflicted cadastral lines by cross-point calculation. Calculating cross-point number and moving distance and direction for each conflicted cadastral lines;
- Moving the conflicted cadastral lines based on calculated cross-point number and moving distance;
- Related cadastral line adjustment.
- Searching the conflicted cadastral lines
We use the cross-point between cadastral lines and building lines to search the conflicted cadastral lines. For each cadastral line, we calculate the cross point between cadastral lines and building lines. The cross-point must be a real cross-point within the given line segments and not on their extension lines. Then we count the cross-point numbers and calculate the maximum distance (and its direction) of each minimum distance between cross-points and end points of building lines.
- Moving the conflicted cadastral lines
If the cross-point number is big or equal to two and the moving distance is smaller than the given limited distance, we move this cadastral line by calculated moving direction and distance plus alpha. If the cross-point number is equal to one (it means that the end point of cadastral line is located inside a building nd the moving distance is larger than the given limited distance (it means that the crossed building has some problem, such as merged or generalized by several small buildings), we do not move this cadastral line. These problems will be checked and modified by operator editing.
- Related cadastral line adjustment
The plirocessing is similar with boundary line processing and includes following four parts:
- Searching the related cadastral lines based on the end pints;
- Moving each one of end pint on the conflicted cadastral lines to new points;
- Adjusting each another end point on the modified lines checked by the direction changing between new and old lines.
- Sequentially doing above processing until the end.