Lithographic Printing Office (LPO) is one of the most important units of SOB. It is an industrial production unit and plays a vital role in Map production. SOB prints various kinds of maps, charts and forms with modern printing technology.
SOB no longer uses the heavy cumbersome stones but instead use light, flexible metal plates, which have granular surface instead of porosity to hold grease or water. On a stone, grease and water do not have cohesiveness and that is the principle of Lithography. The term “Photolithography” is used to denote using photographic processes in Lithographic plate preparation.
Map Printing: Map production chain starts with taking of aerial photographs and is completed through the process of plotting, editing, cartographic work in the process of map printing includes finally printing, developing film through positive, plate making and paper printing.
In map printing, the original impressions are in 4 colors i.e. CMYK (cyan, magenta, yellow, black) as films are used. The contents are comprised of fine lines and points having accurate orientation.
In the case of maps, plate/ film impression to the final product is completely different from that of ordinary picture printing. Further, the original is black or white, so the final image of the map can only be realized during the stage of making map original. Thus, the workmanship and the quality of maps can only be judge after the completion of the map printing and duplicates through the map printing process.
Offset press: There are two technologies for transferring ink from the image area of the plate to the paper. One technique is (i) direct printing in which ink is directly transferred from the plate to the paper and other technology is (ii) offset printing in which the ink is first transferred from the plate to a rubber cylinder and than from the rubber on the paper.
According to the offset method, ink is transferred from a soft rubber cylinder to paper, so that fine printing is possible even on rough paper. Handing of plate materials (aluminum PS plate) is also easier. At present SOB is using modern offset press. It has fully computerized control self diagnosis system. Its printing speed is about 16,000 sheets/ hour.
In digital printing, computer to plate (CTP) technology is used in advanced countries. SOB is also going to acquire this technology soon. Instead of making film positives, it will directly make plates of desired colors from computer cartographic map data. Advanced countries use this technology since long and even the Mapping Organizations of developing countries use this CTP technology. Once the technology is incorporated in SOB’s production line, it would enhance the quality and productivity of map printing.
Digital 2-color Offset Press, LITHRONE GL-240
Map paper: Generally SOB uses litho or mat paper for map printing. Besides those, other common types of paper are also used when required.
Color: The three primary colors are Red, Green and Blue (RGB). However, the three colors for printing ink are Cyan, Magenta and Yellow (CMY).
The relation between the three primary colors and three the three primary colors of printing ink is C=white – R, M=white – G, and Y=white- B. At present SOB uses CMYK for printing maps in digital offset press.
The necessity of modern printing equipment was being felt for last few years. Implementation of the project for supply of cartographic equipment supported by JICA fulfilled that demand and hence it may be mentioned as a greater step towards modernization of the printing office of SOB.
With satisfaction to note that Map printing is the final step of production chain of map making. At present SOB enjoys state of the art printing capacity. In addition to serving the needs of SOB, the printing services are also rendered to other government department like Bangladesh Metrological department, Bangladesh Air Force, Department of Land Records and Surveys etc.