One is digitization, that is, the field measurement data or the digitized data of the map are manually input, which is the most accurate way to build the database at present.
The second is to link from the old MIS system, but this is limited to attribute data.
The third way is through remote sensing images, which is the cheapest and most efficient way to obtain. However, due to the lack of development of ground target recognition technology, the accuracy is limited. For example, in the pipeline geographic information system, the water pipes and gas pipes inside cannot be put into storage by remote sensing.