Transform and projection of digital map based on South Cass survey software

As differences exist in zoning of medium and small scale maps,projection distortion can not be avoid in the process of transform and projection of digital maps.The conventional control measures for projection distortion are dividing the original digital map into several sub maps,and through translation and rotation or adding scale distortion,the sub maps are linearly transformed,which has the disadvantage of heavy workload,large error and mistakes-prone.Using South Cass survey software and combining with self-developed program to conduct transform and projection of digital maps,we successfully solve the difficulties of splicing maps with different projection zoning,which has the advantages of idea applicability and strictness.