Expandable base and engineering surveying and mapping automatic telescopic box staff

The invention relates to the field of engineering surveying and mapping, in particular to an extensible base and an automatic telescopic box staff for engineering surveying and mapping. The ruler body structure comprises a first section fixed on the bottom plate, a second section sleeved with the first section in a sliding manner and a third section sleeved with the second section in a sliding manner; wherein a first elastic locking mechanism is arranged between the first section and the second section and can maintain the locking state between the first section and the second section, and a second elastic locking mechanism is arranged between the second section and the third section and can maintain the locking state between the second section and the third section. The second elastic locking mechanism can maintain the locking state between the second section and the third section, during use, the stability of the bottom plate can be automatically enhanced according to the overall height of the ruler body st