LiDAR data processing was used to produce the x,y,z elevation points using vendor proprietary lidar data processing software. Within this integrated process an atmospheric correction was made, which is especially important in regions of relatively low elevation.
Data by flight line was combined in a merge process that eliminates redundant points. Data was also clipped into more manageable one km x one km bounds. Noise or anomalous returns were filtered from all data during this processing step. The data was quality checked using commercial software, Spectra Precision TerraModel and TerraVista.
All elevation data was processed on a point by point basis for ellipsoid to orthometric height conversion using the National Geodetic Survey (NGS) Geoid Model, GEOID99. Datum and coordinate system conversion from WGS84 to the Washington State Plane coordinate system was performed using U.S. Army Corps of Engineers CorpsCon software algorithms.
First and last return intensity point data was transferred to media for delivery to client in a comma/space delimited ASCII file of format easting,northing,intensity-value. Image format was generated through histogram-equalization of the variably-spaced points and conversion to GeoTIFF format, with world file.
After receipt and logging of media, the GeoTIFF images were transferred to on-line access location. ArcInfo 7.x operating on a Unix platform was used to convert each TIFF image to a grid using the IMAGEGRID command. The grids were merged to create a single composite grid for each delivery. GRIDIMAGE was used to convert the grid to a TIFF for quality evaluation and continuity check.
The individual delivery grids were mosaiced using GRID MERGE to create contiguous grids. Areas that did not have intensity values to the full extent of the tiles of idxptrmbr index were filled with 255 value background. The composite grids were clipped using GRID GRIDCLIP to the extents of their respective tiles. PROJECTDEFINE define the projection header and GRIDIMAGE was used to convert the GRID tiles to TIFF with world file.
The output TIFF images were compressed to jp2 format using JPG2000 compression software with a compression ratio of 5. This was done to minimize storage space requirements while preserving the data as lossless.
ASCII data as delivered by vendor was tiled in an approximate 1km x 1km tiling scheme based on a vendor UTM-based grid. The ASCII data was not reformatted but only retiled to KC standard scheme based on Stateplane 7500 ft x 7500 ft grid.
From original vendor index, vendor tiles required for new 7500 tile were identified. Data files were awked to add a constant value of 1 into a lead column followed by remaining original x, y, intensity-value columns.
All awked files were cocantenated into single file and submitted to ArcInfo command-line CREATETIN command with zero (0) filtering (weed) tolerance and bound arguement of subject 7500 tile.
Created TIN was ungenerated to point coverage using TINARC command and coordinate values were assigned to each point using the ADDXY command. In TABLES, coverage was selected and X-coord, Y-coord and SPOT value (intensity value) were unloaded to 'tile-name'kc_lri.asc and 'tile-name'kc_fri.asc, for last-return and first-return data, respectively.
Even with zero filtering tolerance, some points were dropped during the TIN process though the lost points is considered insignificant.
For quality control, the TIN was converted to a lattice using the TINLATTICE command and a hillshade created using the HILLSHADE command. The hillshade grid was converted to a tif image using the GRIDIMAGE command and was inspected for general quality and tile bound consistency.
Retiled ASCII point files were compressed using a zip compressing routine and stored in the Spatial Data Warehouse.
This MBR is defined by right angle corners and four orthogonal bounds that are adjusted to the nearest 100 foot State Plane Zone 5061, HPGN position. This results in a series of overlapping tiles that fully encompass all sections within that township. The tiling scheme is defined by the spatial index called idxptrmbr (index polygons for township- range, minimum bounding rectangle).
The ASCII data is provided in a standardized tiling scheme based on a 7500x7500 foot Stateplane grid in column-row format. Tiles are identified as ab01,ab02,....az01,az02....ba01,ba02...
\\gisdw\kclib\plibrary3\idxp7500\intensity_firstret (tif image data) \\gisdw\kclib\plibrary3\idxp7500\intensity_lastret (tif image data)
\\gisdw\kclib\plibrary3\idxp7500\lri_ascii (ASCII data) \\gisdw\kclib\plibrary3\idxp7500\fri_ascii (ASCII data)