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Karen Kwsanowski
GroundPoint Technologies LLC
Chief Technical Officer
315-459-1515
17 Highland Dr
Marcellus
NY
13108
US
20210831
ArcGIS Metadata
1.0
Los Angeles County
999-999-9999
Not available
Not available
PA
99999
US
withheld
Enterprise Geodatabase Feature Class
elevation_contours
2016-04-15
Karen Kwasnowski
document
<DIV STYLE="text-align:Left;"><DIV><P><SPAN>Lidar Data Products for the LA County, CA collection area includes a 3ft DEM, 2ft or 1ft Contour tiles, Voids in the Ground Surface >= 8 meters squared (86.11 ft squared), Voids in the 1st Return Surface >=4meters squared (21.703 ft squared), Hydrographic Breaklines, Percent Slope, Degree Slope, and a 3ft Digital Surface Model (DSM) of the 1st return lidar surface and a normalized DSM (Height Above Ground)).</SPAN></P></DIV></DIV>
The lidar dataset was collected to be utilized for the creation of a digital elevation model, 2ft or 1ft contours, hydrographic breaklines, slope rasters and a digital surface model. Other uses expected.
Thom S. Salter
Pictometry International Corp.
Manager, Photogrammetric Production
585-486-0093
585-486-0098
100 Town Centre Drive, Suite A
Rochester
NY
14623
US
0900-1700
Geographic Names Index Service
Los Angeles County
California
EDI Thesaurus
LiDAR
LiDAR
Los Angeles County
California
See access and use constraints information.
Access to this data is constrained by the license agreements between Pictometry International and LA County, CA
<DIV STYLE="text-align:Left;"><DIV><P><SPAN>Access to this data is constrained by the license agreements between Pictometry International and LA County, CA.</SPAN></P></DIV></DIV>
Esri ArcGIS 12.7.0.26828
-112.125088
-111.678816
43.623514
43.78476
-6.608500
288.792500
Publication Date
2016-01-01
-6.608500
288.792500
1
-118.253104
-118.244371
34.010134
34.002861
-6.608500
288.792500
Access to this data is constrained by the license agreements between Pictometry International and LA County, CA.
Visual checks were used to make sure all features and feature classes are complete.
Visual checks were used to make sure all features and feature classes are complete.
Breaklines for hydrographic features are digitized using 2015 aerial ortho photos and the 2015 lidar data both supplied by Pictometry International. The hydrographic features, include water bodies (> 0.5acres), wide rivers and channels (> 16ft wide), an artifical path representing the centerline of the wide rivers and waterbodies, stream centerlines (drainage features < 16ft wide), culverts, and a shoreline for the ocean. Elevation values from the lidar data are conflated to the “z-values” of the features at a 6ft interval in areas that require 2ft contour mapping and a 3ft interval in areas that require 1ft contour mapping using QCoherent’s LP360 software. Elevation values are conflated to the Single Line Stream, Artifical Path, and Culvert features using a downstream constraint algorithm. After the artificial paths are conflated, the lp360 flatten polygon tool is used to copy the elevation values from the vertices of the artificial path to the corresponding vertices of the wide river polygons, which flatten the wide river from streambank to streambank. Elevation values for the water body polygons are added as an attribute to the feature class based on the minimum lidar elevation value along the shoreline of the water body. In order to flatten the oceanic water an analysis is made to determine the best approximate elevation value, which accounts for the multiple range of elevation valuesalong the shoreline as the data is collected at different tidal heights. A value of negative one is determined to be the best value for this collection. Lidar ground points that are completely within waterbodies and widerivers are reclassified to Class 9 (Water), and lidar ground points within a 3' buffer of waterbodies, widerivers, and centerlines are reclassified to Class 20 (reserved). The remaining ground points, water bodies, widerivers, and centerlines are used to create a bare earth surface (DTM) with 6ft cell resolution. Percent Rise and Degree slope rasters are created from this DTM. The DTM is also used to create the 2ft or 1ft tiled contours. The contours are edited in the following manner: Lines shorter than 36ft (1.5 raster cells) are removed for 2' contours and lines shorter than 18' are removed for the 1' contours. The shape of contour lines along the edge of water ways are checked to make sure they do not weave into the waterways. Attributes are added for 10ft, 20ft, and 50ft Index contours. A Lidar Tile Index Feature Class is created for the lidar files. Voids: The void analysis is based on the FEMA specifications for the Ground Point data and USGS American National Geospatial Program Lidar Base Specification v1.2 of 2014 for the 1st Return data. The USGS specification states that Data Voids => 4*Nominal Post Spacing in the 1st return lidar points is unacceptable in a single lidar swath except where caused by water bodies, areas of low infrared reflectivity, or where filled in by another swath. The FEMA specification defines data voids as Ground areas that are not within two times the DEM posting of data points, which equates to 4m for the 2ft contour interval accuracy standard. Data voids are acceptable over bodies of water or where points have been removed over man-made structures. Data voids are not acceptable with LiDAR system malfunction or flight error. Data voids need to be flagged in areas where LiDAR points have been removed due to dense vegetation. If the data voids in areas of dense vegetation are less than 1 acre then the voids may usually be filled by interpolation. If the data voids are greater than 1 acre then cross sections must be cut to fill the void areas. The lidar ground points are converted point shapefiles and then to raster with a 9.28ft (~2.83m) cell size. The 1st Return lidar points are converted to point shapefile and then to raster with a 4.66ft cell size. The rasters are reclassified as NoData: 1 and Any_Value: NoData. The reclassified rasters are converted to polygon. Attributes are added for ‘Acreage” and “LandCover”. For the Ground surface, data voids > 1 acre are noted for landcover type using Pictometry imagery. Digital Surface Model (DSM): For the DSM, the Lidar Data is converted to a raster with a filter for 1st returns using Unclassified, Ground, Model Key Points, and Water classes with a 6ft cell size. The DSM and DEM are checked to make sure the cells align with one another. A normalized DSM is created by subtracting the DEM from the DSM to obtain the height above ground. Hillshades are also created for the DEM and DSM using default illumination parameters.
2016-04-15
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