In the first Swiss National Forest Inventory aerial photography was not used in a sense of multiphase or multistage sampling. In the second NFI the use of a two-phase sampling design is planned to increase efficiency.
The results of a pilot survey in the canton of Ticino (southem Alps) are presented. The test area is characterized by large variation in both standing volume and elevation. Double sampling with regression estimates and double sampling for stratification are compared. Regarding cost and standard error, two-phase sampling for stratification is much more advantageous.