Difference Between TIN Filter and TILE Filter

 Applies To 
 Environment: N/A
 Area: Data Acquisition
 Original Author:Jacquelyn Pettus, Bentley Technical Support Group










What is the difference between the TIN filter and the TILE filter when importing LIDAR data into Data Acquisition?


The Tile Filter uses an algorithm that divides the LIDAR data set into tiles. A best fit plane is calculated for each tile, and LIDAR points are removed if they fall within the user set Z tolerance to the plane.

The TIN Filter first separates the LIDAR points into tiles with a maximum of 2 million points and then repetitively triangulates each tile, filtering out points.  The TIN Filter algorithm filters out the points if they fall within the user set Z tolerance of the triangle planes.

Z Tolerance - common to both algorithms and is basically the variation in the Z coordinate that the surface is allowed to move during the filtering process.  Typically for the first invocation of the filtering function, the Z tolerance should be set from 0.5 to 1.0 for imperial data sets and from 0.25 to 0.5 for metric data sets.  Depending on the outcome and the desired result, the Z tolerance can be varied up or down.

Max. Tile Points - specifies that a tile will not be subdivided if it has less than this number of points.  Typically this is set to five.

Max. Tile Divisions - the allowable level of recursion allowed and is the number of time the initial tiling set can be subdivided.  Typically this is set to five.

Start Tile Length – The LIDAR data set is initially divided into tiles of this size, prior to recursion to the minimum tile points. The setting of this parameter requires some knowledge of the distance between the LIDAR points, which requires an inspection of the LIDAR points in MicroStation to determine.  Typically set this to 10 times the distance between the LIDAR points.

Course Filter (TIN option only) – Filter more points with some blurring of ridges and valleys

Fine Filter (TIN option only) – Filters fewer points with less blurring of ridges and valleys

Points Before Filter/Points After Filter/Reduction % - Display of the number of points before and after filtering, plus the percentage reduction of points from before and after