There are influences coming form air dynamics in the process of projectile's flying.The motion equation of projectile is very complicated which is caused by the uncertain air dynamics' coefficients.As a result,this article puts forward a simplified model of trajectory equation through the following processes.Firstly,the air dynamics' variance is analyzed by the effect of air dynamics to projectile;secondly,the influences of air dynamics is researched to projectile in the process of flying.To demonstrate the effectiveness of the proposed model,it takes some type high artillery fire for an example to carry out simulation calculation.

Through the analysis of the effect of projectile flying time fitting errors to fire data in the basic firing table,the article puts forward the analytic expressions of firing errors which caused by errors of time fitting.Moreover,it analyzes the effect of flying time fitting errors to elevation and shooting direction errors that adopts five typical flight paths.Then,it advances the relations between fitting errors to fire data errors in the different flight paths shortcut,flight paths elevation,flight paths distance and target velocity,which prepares the evidences to ensure the projectile flying time fitting's precision.

Firing table which established by firing tests and theoretic calculation is the most qualified for projectile movement characteristics.According to firing table's advantage,the article puts forward a model of projectile motion based on firing table fitting,and from this proposes a computing model of undershoot magnitude.To demonstrate the effectiveness of the proposed model,it takes some type high artillery fire for an example to carry out simulation calculation.