2015 Lidar DEM: Allegan County (MI)

This metadata record describes the hydro-flattened bare earth digital elevation model (DEM) derived from the classified LiDAR data for the 2015 Michigan LiDAR project covering approximately 842 square miles, in which its extents cover Allegan County.

The NOAA Office for Coastal Management (OCM) downloaded the MI_25County-AlleganCo_2015 Digital Elevation Model (DEM) files from this USGS site: ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/OPR/ and processed the data to the Data Access Viewer (DAV) and https.

In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEMs were created from, are also available. These data are available for custom download at the link provided in the URL section of this metadata record.

Hydro breaklines are also available. These data are available for download at the link provided in the URL section of this metadata record. Please note that these products have not been reviewed by the NOAA Office for Coastal Management (OCM) and any conclusions drawn from the analysis of this information are not the responsibility of NOAA or OCM.

To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments, and hydrologic modeling. LAS and bare earth DEM data products are suitable for 1 foot contour generation. USGS LiDAR Base Specification 1.0, QL2. 18.13 cm FVA.

The following are the USGS lidar fields in JSON:

{

"ldrinfo" : {

"ldraccur" : {

"ldrchacc" : "1.0",

"rawfva" : "0.161",

"clsfva" : "0.131",

"clscva" : "0.192",

"clssvas" : {

"svalctyp" : "Urban",

"svavalue" : "0.159"

},

"clssvas" : {

"svalctyp" : "LowVeg",

"svavalue" : "0.215"

},

"clssvas" : {

"svalctyp" : "MedVeg",

"svavalue" : "0.192"

},

"clssvas" : {

"svalctyp" : "HighVeg",

"svavalue" : "0.196"

}

FEMA Specification Version QL2 meeting 9.25cm FVA

The State of Michigan Geographic Information Systems digital data have been tested and their documentation carefully reviewed. However, the State of Michigan and its representatives make no warranty or representation, either expressed or implied, with respect to the digital data and their documentation, their quality, performance, merchantability, or fitness for a particular purpose. The digital data are distributed on "as is" basis, and the user assumes all risk to their quality, the results obtained from their use, and the performance of the data. In no event will the State of Michigan or its representatives be liable for any direct, indirect, special, incidental or consequential damages resulting from and defect in the State of Michigan or in their documentation. This disclaimer of warranty is exclusive and in lieu of all others, oral or written, express or implied. No agent or employee is authorized to make any modification, extension, or addition to this warranty.

Any conclusions drawn from the analysis of this information are not the responsibility of the Sanborn, State of Michigan, USGS, NOAA, the Office for Coastal Management or its partners

Data is available online for custom and bulk downloads.

None

This data is for planning purposes only and should not be used for legal or cadastral purposes. Any conclusions drawn from analysis of this information are not the responsibility of Sanborn Map Company. Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations.

Microsoft Windows 7; ESRI ArcCatalog 9.3.1.1850

Horizontal positional accuracy for Allegan LiDAR is dependent upon the quality of the GPS/INS solution, sensor calibration and ground conditions at the time of data capture. The standard system results for horizontal accuracy meet or exceed the project specified 1.0 meter RMSE.

1.0 meter: Allegan County, this value is computed by comparing ground control to a DEM derived from the classified LiDAR data and represents the RMSE of residuals on controls within the project area.

For the DEM data derived from the classified point cloud, the FVA, SVA, and CVA were computed. The vertical accuracy was tested with independent survey check points located in various terrain types within Allegan County. These check points were not used in the calibration or post processing of the lidar point cloud data. The survey check points were distributed throughout the block area. Specifications for this project require that the FVA be 9.25 cm (18.13 cm or better @ 95 percent confidence level).

0.067m RMSE, or 0.131m FVA @ 95 percent Confidence Interval

The FVA was tested using 38 independent survey check points located in flat terrain types within Area 5. The survey checkpoints were distributed throughout the block area. The 38 independent check points were surveyed using static GPS base stations collecting point location for 20 minute intervals. Elevations were measured for the x,y,z location of each check point. Elevations interpolated from the DEM surface were then compared to the elevation values of the surveyed control. The RMSE was computed to be 0.067 m. AccuracyZ has been tested to meet 9.25 cm Fundamental Vertical Accuracy at 95 Percent confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines.

LiDAR data is collected for the project area. Post processing of the simultaneously acquired GPS/INS is performed and applied to the laser returns to output a point cloud in the specified project coordinate system and datums. The point cloud data is then subjected to automated classification routines to assign all points in the point cloud to ground, water, overlap and unclassified point classes. Anomalous laser returns that occur infrequently are removed entirely from the data set. Once clean bare earth points are established, DEMs are created using bare earth points and hydro features. The DEM surface is then compared to the survey checkpoints. These accuracies must pass the Fundamental Vertical Accuracy, Supplemental Vertical Accuracy, and Consolidated Vertical Accuracy specifications.

LiDAR data is collected within the project area and processed. After the DEMs were created, the dataset was verified against control. Control was collected in 5 areas. Area 5 includes Allegan, Berrien, and Van Buren. Accuracy results are reported for Area 5.