In order to render massive terrain data in real time

this paper presents an improved LOD algorithm.This algorithm firstly simplifies the DEM data by using Mortan coding principle and stores the simplified data with an unfull quadtree.Then

it builds the real-time continuous Lod based on this unfull quadtree according to the relationship between viewer position and grid object space error.The authors bring out a method named "find the neighbors layer by layer" to patch the cracks between different layers and the procedures to find the different type neighbors are presented in this paper.Finally

it wipes off the invisible grids through back-culling algorithm.In order to improve the rendering speed

it uses Hilbert filling curve method to store and interleaved quadtree method to access the unfull quadtree nodes.The authors use the improved method to simulate the terrain of Jingjiang area and obtain a good effect.