For manipulating mass and various datum of precision agriculture gathered from different datum sources, an accurate, large scale, digital field base map is needed as a reference. In order to obtain this kind of field base map, several mapping methods were compared and the GPS mapping was carried out. The GPS data were processed and the map was generated in a field-level GIS. For increasing the map accuracy, single point repeated positioning-averaging, and continuously positioning-moving averaging methods of data processing were designed and tested. The test result shows that the map accuracy is about 0.5 m. The map updating was based on RS images. Methods of RS image multinomial digital geometric correction, and RS image coordinate register for field base map updating were introduced.