Worcester County - VA FEMA LiDAR
201108
Unknown
Hydro-Flattened DEMs
map
Dewberry collected LiDAR for ~3,341 square miles in various Virginia Counties, a part of Worcester County, and Hooper's Island. The acquisition was performed by Terrapoint. This metadata covers the LiDAR produced for Worcester County. The nominal pulse spacing for this project is 0.5 meters. This project was collected with a sensor which collects intensity values for each discrete pulse extracted from the waveform. GPS Week Time, Intensity, Flightline and echo number attributes were provided for each LiDAR point. Dewberry used proprietary procedures to classify the LAS according to contract specifications: 1-Unclassified, 2-Ground, 7-Noise, 9-Water, 10-Ignored Ground due to breakline proximity, and 11-Withheld. Dewberry produced 3D breaklines and combined these with the final LiDAR data to produce seamless hydro flattened DEMs for the 263 tiles (6000 ft x 4000 ft) that cover the project area.
The purpose of this LiDAR data was to produce high accuracy 3D elevation products, including tiled LiDAR in LAS 1.2 format, 3D breaklines, and a 2 ft cell size hydro flattened Digital Elevation Models (DEM).
A complete description of this dataset is available in the Final Project Report.
20110305
20110729
ground condition
As needed
-75.311360
-75.047094
38.456610
38.020799
None
DTM
Elevation
Lidar
LAS
DEM
Hydro Flattened
Breaklines
None
Maryland
Worcester County
None
This data was produced for the USGS and FEMA according to specific project requirements. This information is provided "as is". Further documentation of this data can be obtained by contacting: Patrick Emmett, MS 666, 1400 Independence Road, Rolla, MO 65401. Telephone (573) 308-3587.
USGS
Patrick Emmett
mailing and physical address
MS 666, 1400 Independence Road
Rolla
Missouri
65401
United States
573.308.3810
pemmett@usgs.gov
8:00 AM - 5:00 PM
Microsoft Windows Server 2008 R2 Version 6.1 (Build 7601) Service Pack 1; ESRI ArcCatalog 10.0.0.2414
Data covers the tile scheme provided for the project area.
A visual qualitative assessment was performed to ensure data completeness and bare earth data cleanliness. No void or missing data, the bare earth surface is of good quality and data passes vertical accuracy specifications.
Lidar source compiled to meet 3.28 ft horizontal RMSE.
3.28 ft
Dewberry does not perform independent horizontal accuracy testing on the LiDAR. LiDAR vendors perform calibrations on the LiDAR sensor and compare data to adjoing flight lines to ensure LiDAR meets the 3.28 ft horizontal accuracy standard at the 95% confidence level. Please see the final project report for more details.
The DEMs are derived from the source LiDAR. Vertical accuracy is not tested on the DEMs.
The vertical accuracy of the LiDAR was tested by Dewberry with 60 independently collected checkpoints. The survey checkpoints are evenly distributed throughout the project area and cover the three major land cover classifications.
All 60 checkpoints were used to compute the Fundamental Vertical Accuracy (FVA). Project specifications required a FVA of 0.60 ft (18 cm) based on a RMSEz 0.31 ft (9.25 cm) x 1.9600. All checkpoints were also used to compute the Consolidated Vertical Accuracy (CVA). Project specifications required a CVA of 1.19ft (36.3 cm) based on the 95th percentile.
0.43 feet
The DEMs are derived from the source LiDAR. Vertical accuracy is not tested on the DEMs.
Based on the vertical accuracy testing conducted by Dewberry, using NSSDA and FEMA methodology, vertical accuracy at the 95% confidence level (called Accuracyz) is computed by the formula RMSEz x 1.9600. The dataset for the Worcester County project satisfies the criteria:
Lidar dataset tested 0.43 ft vertical accuracy at 95% confidence level, based on RMSEz (0.22 ft) x 1.9600.
Based on the vertical accuracy testing conducted by Dewberry, using NDEP and ASPRS methodology, consolidated vertical accuracy at the 95% confidence level is computed using the 95th percentile method. The dataset for the Worcester County project satisfies the criteria:
Lidar dataset tested 0.90 ft vertical accuracy at 95% confidence level in all land cover categories combined.
Dewberry
20110630
Worcester County - VA FEMA LiDAR
One
map
Fairfax, VA
Dewberry
www.dewberry.com
Hard Drive
201103
201107
Ground Condition
none
LiDAR data representing FEMA Virginia LiDAR Task Order to be used for various analysis and research purposes.
Establishment of survey points to support the LiDAR data collection. Two existing published NGS stations (AI7609, HU2327) were observed in a GPS control network and used to establish four new points for the primary control for this site. 1110312 was observed and used to control all flight missions and static ground surveys. The following are the final coordinates of the control points used for this project: SurveyBlock, Station, Latitude(D M S Hem), Longitude(D M S Hem), H-Ell(m), H-MSL(m) Worcester, 1110312, N38 18 22.12367, W75 07 40.46389, -33.7921, 2.2581
Published_NGS_Coordinates
Raw_Control_GPS
201103
Control_Network
Manager Geospatial Solutions
mailing and physical address
251216 Grogan's Park Drive
The Woodlands
Texas
77380
USA
1-877-80-TERRA
1-281-296-0869
veronique.payan@terrapoint.com
Monday to Friday, 8:30 - 4:30, Eastern Time
Geodigital/Terrapoint
Veronique Payan
Airborne GPS Kinematic processing Airborne GPS kinematic data was processed on-site using GrafNav kinematic On-The-Fly (OTF) software. Flights were flown with a minimum of 6 satellites in view (13o above the horizon) and with a PDOP of better than 4. Distances from base station to aircraft were kept to a maximum of 40 km, to ensure a strong OTF (On-The-Fly) solution. For all flights, the GPS data can be classified as excellent, with GPS residuals of 3cm average but no larger than 10 cm being recorded. The Geoid09 geoid model, published by the NGS, was used to transform all ellipsoidal heights to orthometric.
Control_Network
RAW_GPS_IMU
201103
Processed_Trajectory
Manager Geospatial Solutions
mailing and physical address
251216 Grogan's Park Drive
The Woodlands
Texas
77380
USA
1-877-80-TERRA
1-281-296-0869
veronique.payan@terrapoint.com
Monday to Friday, 8:30 - 4:30, Eastern Time
Geodigital/Terrapoint
Veronique Payan
Mission to mission adjustments of Lidar data All missions are validated and adjusted against the adjoining missions for relative vertical biases and collected GPS static and kinematic ground truthing points for absolute vertical accuracy purposes
Calibrated_LiDAR
201104
Calibrated_LiDAR_VertAdj
Manager Geospatial Solutions
mailing and physical address
251216 Grogan's Park Drive
The Woodlands
Texas
77380
USA
1-877-80-TERRA
1-281-296-0869
veronique.payan@terrapoint.com
Monday to Friday, 8:30 - 4:30, Eastern Time
Geodigital/Terrapoint
Veronique Payan
Dewberry utilizes a variety of software suites for inventory management, classification, and data processing. All LiDAR related processes begin by importing the data into the GeoCue task management software. GeoCue allows the data to retain its delivered tiling scheme (6000 ft by 4000 ft). The tiled data is then opened in Terrascan where Dewberry uses proprietary ground classification routines to remove any non-ground points and generate an accurate ground surface. The ground routine consists of three main parameters (building size, iteration angle, and iteration distance); by adjusting these parameters and running several iterations of this routine an initial ground surface is developed. The building size parameter sets a roaming window size. Each tile is loaded with neighboring points from adjacent tiles and the routine classifies the data section by section based on this roaming window size. The second most important parameter is the maximum terrain angle, which sets the highest allowed terrain angle within the model. Once the ground routine has been completed a manual quality control routine is done using hillshades, cross-sections, and profiles within the Terrasolid software suite. After this QC step, a peer review and supervisor manual inspection is completed on a percentage of the classified tiles based on the project size and variability of the terrain. After the ground classification corrections were completed, the dataset was processed through a water classification routine that utilizes breaklines compiled by Dewberry to automatically classify hydrographic features. The water classification routine selects ground points within the breakline polygons and automatically classifies them as class 9, water. During this water classification routine, points which are in close proximity (1 m) to the hydrographic features are moved to class 10, an ignored ground. In addition to classes 1, 2, 8, 9, and 10, the project allows for a Class 7, noise points. This class was only used if needed when points could manually be identified as low/high points. Dewberry also used Class 11 - Withheld points.
The fully classified dataset is then processed through Dewberry's comprehensive quality control program.
The data was classified as follows:
Class 1 = Unclassified. This class includes vegetation, buildings, noise etc.
Class 2 = Ground
Class 7= Noise
Class 8= Model Key Points
Class 9 = Water
Class 10= Ignored Ground
Class 11= Withheld
The LAS header information was verified to contain the following:
Class (Integer)
GPS Week Time (0.0001 seconds)
Easting (0.01 ft)
Northing (0.01 ft)
Elevation (0.01 ft)
Echo Number (Integer 1 to 4)
Echo (Integer 1 to 4)
Intensity (8 bit integer)
Flight Line (Integer)
Scan Angle (Integer degree)
Processed Lidar datasets in LAS 1.2 format
201107
Finalized LiDAR dataset using Orthometric Heights.
Brian Mayfield
Dewberry - Geospatial Services Group
Project Manager
mailing and physical address
1000 N. Ashley Drive, Suite 801
Tampa
FL
33602
USA
813.421.8628
813.225.1385
bmayfield@dewberry.com
8:00 - 5:00 EST
Mission to mission adjustments of Lidar data All missions are validated and adjusted against the adjoining missions for relative vertical biases and collected GPS static and kinematic ground truthing points for absolute vertical accuracy purposes
Calibrated_LiDAR
201104
Calibrated_LiDAR_VertAdj
Manager Geospatial Solutions
mailing and physical address
251216 Grogan's Park Drive
The Woodlands
Texas
77380
USA
1-877-80-TERRA
1-281-296-0869
veronique.payan@terrapoint.com
Monday to Friday, 8:30 - 4:30, Eastern Time
Geodigital/Terrapoint
Veronique Payan
Deliverable Product Generation Raw Lidar point were reprojected from UTM zone 18 to the delivery projection State Plane Maryland, US Survey Feet. *Raw Calibrated LIDAR Point Cloud Raw LiDAR point cloud, was provided in the following formats/parameters: - LAS V1.2, point record format 1, Adjusted GPS time, georeferencing information populated in header - The following fields are included in the LAS file: 1. Adjusted GPS time reported to the nearest microsecond 2. Flight line ID 3. Easting (reported to the nearest 0.01m) 4. Northing (reported to the nearest 0.01m) 5. Elevation (reported to the nearest 0.01m) 6. intensity 7. Echo number 8. Classification 9. Scan angle 10. Edge of scan 11. Scan direction - Full swaths, all collected points delivered (except discarded flightline) - The Withheld bit flags the last 3 degrees of the swath - 1 file per swath, 1 swath per file (except when swath had to be divided in section for size or calibration).
VertAdj_Calibrated_LiDAR
201105
Client_deliverables
Manager Geospatial Solutions
mailing and physical address
251216 Grogan's Park Drive
The Woodlands
Texas
77380
USA
1-877-80-TERRA
1-281-296-0869
veronique.payan@terrapoint.com
Monday to Friday, 8:30 - 4:30, Eastern Time
Geodigital/Terrapoint
Veronique Payan
Dewberry utilizes a variety of software suites for inventory management, classification, and data processing. All LiDAR related processes begin by importing the data into the GeoCue task management software. GeoCue allows the data to retain its delivered tiling scheme (6000 ft by 4000 ft). The tiled data is then opened in Terrascan where Dewberry uses proprietary ground classification routines to remove any non-ground points and generate an accurate ground surface. The ground routine consists of three main parameters (building size, iteration angle, and iteration distance); by adjusting these parameters and running several iterations of this routine an initial ground surface is developed. The building size parameter sets a roaming window size. Each tile is loaded with neighboring points from adjacent tiles and the routine classifies the data section by section based on this roaming window size. The second most important parameter is the maximum terrain angle, which sets the highest allowed terrain angle within the model. Once the ground routine has been completed a manual quality control routine is done using hillshades, cross-sections, and profiles within the Terrasolid software suite. After this QC step, a peer review and supervisor manual inspection is completed on a percentage of the classified tiles based on the project size and variability of the terrain. After the ground classification corrections were completed, the dataset was processed through a water classification routine that utilizes breaklines compiled by Dewberry to automatically classify hydrographic features. The water classification routine selects ground points within the breakline polygons and automatically classifies them as class 9, water. During this water classification routine, points which are in close proximity (1 m) to the hydrographic features are moved to class 10, an ignored ground. In addition to classes 1, 2, 8, 9, and 10, the project allows for a Class 7, noise points. This class was only used if needed when points could manually be identified as low/high points. Dewberry also used Class 11 - Withheld points.
The fully classified dataset is then processed through Dewberry's comprehensive quality control program.
The data was classified as follows:
Class 1 = Unclassified. This class includes vegetation, buildings, noise etc.
Class 2 = Ground
Class 7= Noise
Class 8= Model Key Points
Class 9 = Water
Class 10= Ignored Ground
Class 11= Withheld
The LAS header information was verified to contain the following:
Class (Integer)
GPS Week Time (0.0001 seconds)
Easting (0.01 ft)
Northing (0.01 ft)
Elevation (0.01 ft)
Echo Number (Integer 1 to 4)
Echo (Integer 1 to 4)
Intensity (8 bit integer)
Flight Line (Integer)
Scan Angle (Integer degree)
Processed Lidar datasets in LAS 1.2 format
201107
Finalized LiDAR dataset using Orthometric Heights.
Brian Mayfield
Dewberry - Geospatial Services Group
Project Manager
mailing and physical address
1000 N. Ashley Drive, Suite 801
Tampa
FL
33602
USA
813.421.8628
813.225.1385
bmayfield@dewberry.com
8:00 - 5:00 EST
Dewberry used GeoCue software to develop raster stereo models from the LiDAR intensity. The raster resolution was 1ft.
Finalized LiDAR dataset using Orthometric Heights.
201107
Lidar Intensity Stereopairs
Brian Mayfield
Dewberry - Geospatial Services Group
Project Manager
mailing and physical address
1000 N. Ashley Drive, Suite 801
Tampa
FL
33602
USA
813.421.8628
813.225.1385
bmayfield@dewberry.com
8:00 - 5:00 EST
LiDAR intensity stereopairs were viewed in 3-D stereo using Socet Set for ArcGIS softcopy photogrammetric software. The breaklines are collected directly into an ArcGIS file geodatabase to ensure correct topology. The LiDARgrammetry was performed under the direct supervision of an ASPRS Certified Photogrammetrist. The breaklines were stereo-compiled in accordance with the Data Dictionary.
The data dictionary defines Tidal Waters as the land and water interface at the time of LiDAR acquisition of tidally influenced bodies of water. There is no minimum area requirement. Tidal variations over the course of a collection or between different collections will result in discontinuities along shorelines. This is considered normal and these "anomalies" should be retained. Variations in water surface elevation resulting in tidal variations during a collection should NOT be removed or adjusted, as this would require either the removal of valid, measured ground points or the introduction of unmeasured ground into the DEM. The USGS priority is on the ground surface, and accepts there may be occasional, unavoidable irregularities in water surface.
Breaklines must be captured at or just below the elevations of the immediately surrounding terain. Under no circumstances should a feature be elevated above the surrounding LiDAR points.
If it can be reasonably determined where the edge of water most probably falls, beneath the dock or pier, then the edge of water will be collected at the elevation of the water where it can be directly measured. If there is a clearly-indicated headwall or bulkhead adjacent to the dock or pier and it is evident that the waterline is most probably adjacent to the headwall or bulkhead, then the water line will follow the headwall or bulkhead at the elevation of the water where it can be directly measured. If there is no clear indication of the location of the waters edge beneath the dock or pier, then the edge of water will follow the outer edge of the dock or pier as it is adjacent to the water, at the measured elevation of the water.
Breaklines shall snap and merge seamlessly with linear hydrographic features.
Lidar Intensity Stereopairs
201107
3D breaklines
Brian Mayfield
Dewberry - Geospatial Services Group
Project Manager
mailing and physical address
1000 N. Ashley Drive, Suite 801
Tampa
FL
33602
USA
813.421.8628
813.225.1385
bmayfield@dewberry.com
8:00 - 5:00 EST
Class 2, ground LiDAR points are exported from the LAS files into an Arc Geodatabase (GDB) in multipoint format. The 3D breaklines, are imported into the same GDB. An ESRI Terrain is generated from these inputs.
Lidar Ground Points, Class 2
3D Breaklines
201107
ESRI Terrain
Dewberry - Geospatial Services Group
Brian Mayfield
Project Manager
mailing and physical address
1000 N. Ashley Drive, Suite 801
Tampa
FL
33602
USA
813.421.8628
813.225.1385
bmayfield@dewberry.com
8:00 - 5:00 EST
The ESRI Terrain is converted to a raster. The raster was created with a 2 foot cell size.
ESRI Terrain
201107
Hydro Flattened DEMs
Dewberry - Geospatial Services Group
Brian Mayfield
Project Manager
mailing and physical address
1000 N. Ashley Drive, Suite 801
Tampa
FL
33602
USA
813.421.8628
813.225.1385
bmayfield@dewberry.com
8:00 - 5:00 EST
Raster
Grid Cell
82,000
39,000
2
NAD 1983 NSRS2007 StatePlane Maryland FIPS 1900 Ft US
38.3
39.45
-77.0
37.66666666666666
1312333.333333333
0.0
coordinate pair
0.000000027061342056100563
0.000000027061342056100563
Foot_US
D NAD 1983 NSRS2007
GRS 1980
6378137.0
298.257222101
North American Vertical Datum of 1988
0.000328
feet
Explicit elevation coordinate included with horizontal coordinates
USGS
Patrick Emmett
mailing and physical address
MS 666, 1400 Independence Road
Rolla
Missouri
65401
United States
573.308.3587
pemmett@usgs.gov
8:00 AM - 5:00 PM
Downloadable Data
This data was produced for the USGS according to specific project requirements. This information is provided "as is". Further documentation of this data can be obtained by contacting: USGS/NGTOC, 1400 Independence Road, Rolla, MO 65401. Telephone (573) 308-3587.
201106
USGS
Patrick Emmett
mailing and physical address
MS 666, 1400 Independence Road
Rolla
Missouri
65401
United States
573.308.3587
pemmett@usgs.gov
8:00 AM - 5:00 PM
FGDC Content Standards for Digital Geospatial Metadata
FGDC-STD-001-1998
local time
http://www.esri.com/metadata/esriprof80.html
ESRI Metadata Profile