lasers best for flood predictions - best laser level for builders

According to a report from the National Research Council of the United States, airborne laser systems should be used to assess flood risk more accurately.
The United States spends more than dollars;
Flood upgrades and digitization 0. 2 billion per year
General map for emergency plan and insurance.
However, the report states that the existing land elevation data are not sufficient to provide accurate maps of hazardous areas.
In flat areas, the measurements should be within 30 cm, more than 10 times that of the existing numbers, which have been decades old.
Laser pulse emission from low level