2. Flood ins/Pacific Intnl Eng - Laserfiche WebLink

Page 4 of 7 Pacific International Engineering Maple River - Phase I Proposal July 18, 2003 (1) Pre-processing Stage During this stage of LiDAR processing, the GPS, IMU, and timed reflection data are processed together using LiDAR pre-processing software. Pre-processing of LiDAR corrects for rotational, atmospheric, and elevation difference that are inherent to LiDAR data sets. This process is called bore-sighting. This is an iterative process which involves analyzing raster difference calculations to determine the proper Omega, Phi, and Kappa angle corrections of the LiDAR instrument. The final stage of pre-processing is the projection of the data to the specified coordinate system. (2) Post-processing Stage The post-processing stage of LiDAR data is organized to remove less accurate edge data, subset the total database into more manageable data sets, and prepare the data for automated and manual feature classification. The post-processing begins with the removal of overlap between adjacent flight lines and trimming the data to the digital project boundary. Data is processed through a minimum block mean algorithm to classify the points to either bare earth or non-bare earth. The determination of the best bare earth model is derived from user developed 'macros' that factor mean terrain angle and height from ground to re-classify points. (3) Manual Feature Classification Stage The manual feature classification ('surfacing') process is a semi-autonomous procedure to determine which data has been correctly classified in the automated feature classification algorithm. The surfacing process is a 2-D edit and quality assurance procedure that ensures the accuracy of the automated feature classification. - Planimetric Map Compilation - Planimetric mapping is not covered under Phase I operations. This will be covered in Phase II. - Orthophotography - Digital orthophotography of the requested area will be provided in the format specified in the deliverables section of this document. The final orthophotography will be tone-balanced and mosaicked to reduce the visibility of seam lines between adjacent exposures of photography. The following components will be utilized in the production of the orthophotography: digital images · digital elevation model · exterior orientation data · camera calibration data The orthorectification process will produce georectified imagery with correction of distortions due to relief and tip/tilt. The orthophotography will meet National Map Accuracy Standards for the scale specified below.