Draft operational guidelines of digital india land records modernization programme (dilrmp) introduction

7.3 Vectorizing, topology building and data integration:
7.3.1 The raster data may be converted to vector data using raster-to-vector converting software. This software works in three distinct methods as mentioned below:

1. 
   Fully automated method
   
2. 
   Semi-automated method
   
3. 
   Completely manual method
   

The Semi-automated method is preferable, because traverse lines may have some breaks which can be corrected through this method during the process of vectorisation, but which create problems with the fully automated method.
7.3.2 No plot on the map is isolated; hence one should posses some knowledge about its adjacent plots. That is why topology building is necessary. This is done by treating each intersecting point as a node. Overshoot, undershoot and duplicate lines are the major problems, which are to be eliminated during the process of topology building. The overshooting lines are deleted and the undershooting lines are extended to their nearest node.
7.3.3 Non-spatial data (plot number, area, etc.) are included in the database containing the spatial data for the map, during the process of data integration.
7.4 Testing of correctness of the digitized map:
7.4.1 The printed copy of the digitized map should be thoroughly checked so that all the plot boundaries and other line works match with the original like a contact print. Plot numbers assigned should also match with the original. In-situ alamats should be placed at exactly the same points as they are located in the original map. A glass table, lighted from below, is used to match such accuracy.
7.4.2 Software checking is done through the “Map Management System” software developed by the NIC to find all the files deliverable for a map sheet.
8. Map composition and query retrieval:
8.1 Different layers (point, line, area) are used for map composition. Line layers are required for the map composition part, while area layers are mainly required for both map checking and composition. However, map composition not only involves construction of the map from a particular layer, but also the inclusion of various non-map features such as the legend for the map, the label of the map specifying its identification from the point of view of Police Station Code, Jurisdiction List Number, etc., bata information for the mouza, the authentication seal of the Government, etc. and various geographical features (the alamats) such as the railway lines, the traverse stations, letter boxes, etc., which can be represented by symbols. The NIC West Bengal State Unit has developed software to compose map by integrating different layers and alamats.
8.2 The non-map features are mostly available in the form of images. A point layer is provided for the insertion of these images. The point layer contains the coordinates of the points where the images are to be positioned. During map composition, the images are to be placed on the map (already composed from the line layer) at their appropriate positions. The geographical features (alamats) can be displayed on the map by using the line, area and point layers. Specific symbols are used for this purpose and the layers contain information regarding these symbols. The final output is a completely composed map identical to the original one.