|
|
|
Poster Session
|
A Topographic contour lines reading system
Line following
- The Procedures of Line Following
Topographic map is so complex with heavy load of geographic information. It is difficult to realize fully automatic map reading at the present time. However appropriately applying pattern recognition technology to get the accuracy and efficiency higher than manual operation is possible. In order to suit different topographic type two procedures for contour lien following were designed:
- Automatic lien detection aided by a few scattered manual pointing.
Manual pointing is needed only at obvious bend of contours line (Fig. 3). Off-course less than a half internal of contour is accepted and the deviation will be corrected automatically.
- Automatic line following with manual directing at interrupted point
At the point where automatic processing fails, the system generates a sound to ask for interactive operation. Manual pointing can also be appropriated.
- Line following with Multi-criterion
There are many algorithms to be used for lien following. One of them is shown in Fig. 4. The central pixel in the image window indicated a point on a contour lien has just been detected. In order to find the next point, sums of 10 pixels on every bar of the 8 directions are calculated and compared. The minimum one is taken as the advanced direction. Though this criterion results are right in most case, mistakes are frequently found. Other algorithms shall be used, such as circuit detection, Laplacians criterion, Hough Transfer and different mistakes may be found. Based on facts that different criterion has different advantage points (3) (4), a new method called multi criterion line following is applied. The principle of this method can be described as follows:
- Any confirm should be through more than two criteria.
- The criterion which is successful at last point will be first applied for the present point. When a criterion fails, another will function automatically. The manual interactive operation is arranged at last of the queue.
- The system s integrated by a series of algorithms, in which, any new algorithms is easy to be accepted for system updating.
Fig.3 Manual pointing
Fig.4 Line following
|
|
|
|
|
|
|
