Based on the practical experiences we learned from "5·12" Wenchuan Earthquake relief works

the paper discusses some key technical issues on data acquisition and post-processing arising from the airborne LIDAR system when it is applied to rapid response.After briefly introducing the basic principles of LIDAR technology and its post-data processing work flow

several key technical issues concerning data acquisition and processing are expounded:（1） Ssystem calibration

which is actually important to all scenarios when LIDAR system is to be used;（2） Flight planning

the first and is also the key step as for high accuracy data acquisition.A good flight plan is of great importance

especially when LIDAR system works in hilly areas with high relief

where weather condition is often complicated as well;（3） Ground GPS base station setting up.GPS base station

which is necessary if POS system is adopted and high positioning accuracy is demanded.Several requirements should be satisfied;（4） Conditions for observation

including topographical condition

weather condition and forestry covering

all of which can influence the accuracy of the final results;（5） The choice of LIDAR hardware systems.Though several commercial LDIAR systems can be selected

we should bear in mind that each system has its pros and cons.Observation conditions have to be taken into consideration

especially when the LIDAR system is to be used over the hilly areas

such as in Sichuan Province;（6） The choice of laser power emission.As an active sensor system

LIDAR emits power by itself.However

there is a limitation as how much power is emitted.When lower power is emitted

it may lack of energy that signals can not be reflected by ground objects

so no echoes recorded.On the other hand

if raising power emission to a very high level

it is harmful to the hardware components of the system.So the optimal choice is a must.Some achievements using the Leica ALS50 second generation LIDAR system are listed in the latter section

which show the airborne LIDAR technology is an efficient and practical way to obtain high accuracy DEM data for South-western China.Some conclusions are summarized in the last section

including:（1） LIDAR system can acquire raw data under complex topographic and bad weather conditions;（2） LIDAR technology is the best choice for accurate DEM data acquisition in hilly areas with high relief and heavy forest;（3） data post-processing is time efficient and shows its satisfaction for rapid response applications.The works described in the paper is helpful to similar natural hazard relief works

and the technical issues discussed in the paper can be referenced by other similar projects.