A new design for measuring directional radiant temperature and data analysis

Abstract

We have designed a new automatic multi-angle observation device to improve the accuracy of measurement and to reduce the uncertainty from the measuring of directional thermal radiation The uncertainty in multi-angle thermal remote sensing is mainly due to the variance of components in the field of view of the sensor with the view angle changing and the heat balance change on the ground during the period of measurement. Using the device we present two new observation methods named as constant area method by thermal and concurrent method by dual sensors respectively. We adopted a portable non-frozen thermal camera that can obtain 50 to 60 thermal images at most in one second. The directional radiometric temperature and the four components of ground objects can be measured by means of the thermal camera installed on the device, which includes four parts: (1) a half circle trackway with 2 m diameter to change azimuth, (2) an elevator for changing the measuring level, (3) a thermal camera on a rotating mast for changing the zenith angle, and (4) a fixed mast installed with another thermal radiometer for measuring the radiometric temperature change process with time. All parts can be disassembled for transport. A computer system controls speeds of moving and rotating. It can supply a moment of 400 kg-cm to drive a 2 m long mast and the 1.5 kg thermal camera. It takes about 2 minutes for the device to finish the measurement from 72/spl deg/ zenith angle to minus 72/spl deg/ zenith angle. Generally, we need only 20 to 40 thermal images for one azimuth angle. It turns out to be an ideal multi-angle observation device for directional radiometric temperatures. The analysis of the major factors in the directional thermal radiation is conducted.