U.S. Geological Survey 201601 Unknown Independent Survey Checkpoints vector data Leading Edge Geomatics (LEG) collected 994 square miles in the Virginia counties of Accomack and Northampton. The nominal pulse spacing for this project was 1 point every 0.7 meters. Dewberry used proprietary procedures to classify the LAS according to project specifications: 0-Never Classified, 1-Unclassified, 2-Ground (bare earth points identified as Model Key Points are flagged with the Model Key Point bit), 7-Low Noise, 9-Water, 10-Ignored Ground due to breakline proximity, 17- Bridge Decks, 18-High Noise. Dewberry produced 3D breaklines and combined these with the final LiDAR data to produce seamless hydro flattened DEMs for the project area. The data was formatted according to the VBMP tile naming convention with each tile covering an area of 5,000 feet by 5,000 ft. A total of 1375 LAS tiles and 1310 DEM tiles were produced for the entire project. The purpose of this LiDAR data was to produce high accuracy 3D elevation products, including tiled LiDAR in LAS 1.4 format, 3D breaklines, and 2.5 feet cell size hydro flattened Digital Elevation Models (DEMs). All products follow and comply with USGS Lidar Base Specification Version 1.2. A complete description of this dataset is available in the Final Project Report that was submitted to the U.S. Geological Survey. 20150511 20150515 ground condition Complete As needed -76.093949 -75.227100 38.064707 37.062181 None Elevation Lidar LAS DEM Hydro Flattened Breaklines Bare earth Checkpoint None Virginia Eastern Shores Accomack County Northampton County USA None This data was produced for the U.S. Geological Survey 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) 308-3810. U.S. Geological Survey Program Manager mailing and physical address
1400 Independence Road
Rolla MO 65401 USA (573)308-3810 pemmett@usgs.gov Microsoft Windows 7 Enterprise Service Pack 1; ESRI ArcCatalog 10.3 Survey checkpoints were collected within the project area boundary. Survey checkpoints were well distributed throughout the project area using a dispersed method of placement. Approximately 50% of the checkpoints were observed twice. Any checkpoints with positional differences greater than 5cm were observed a third time. Existing NGS monuments were located where possible to provide additional checks on the established VRS network. 0.05 m All checkpoint positions are within +/- 5cm of the established VRS network as determined by re-observations on 50% of the checkpoints and comparison of the establisted VRS network to existing NGS monuments. Please see the final project report delivered to the USGS for more details. Approximately 50% of the checkpoints were observed twice. Any checkpoints with positional differences greater than 5cm were observed a third time. Existing NGS monuments were located where possible to provide additional checks on the established VRS network. 0.05 m All checkpoint positions are within +/- 5cm of the established VRS network as determined by re-observations on 50% of the checkpoints and comparison of the establisted VRS network to existing NGS monuments. Please see the final project report delivered to the USGS for more details. Dewberry Consultants, LLC. was under contract to provide 110 QA Check Points for USGS in the state of Connecticut.Three QA Check points were from the Sandy Topobathy project. Under the above USGS Task Order, Dewberry is tasked to complete the quality assurance of high resolution LiDAR-derived elevation products. As a part of this work Dewberry staff completed checkpoint surveys that were used to evaluate vertical accuracy on the bare-earth LiDAR and DEMs. Dewberry field surveyors used Trimble R-8 GNSS receivers which is a geodetic quality dual frequency GPS receiver to collect data at each surveyed location. All locations were occupied once with approximately 50 percent of the locations being re-observed. All re-observations matched the initially derived station positions within the allowable tolerances of 5cm or within the 95 percent confidence level. Each occupation which utilized the VRS network was occupied for approximately three (3) minutes in duration and measured to at least 180 epochs. Each occupation which utilized OPUS (if used) was occupied between 18 and 20 minutes. Field GPS observations are detailed on the Ground Control Point Documentation Reports submitted with the full Survey Report, or Appendix A in the full project report submitted to USGS. Three existing NGS monuments listed in the NSRS database were located as an additional QA/QC method to check the accuracy of the VRS network. Some of these monuments were used as Horizontal and Vertical control checks. Some monuments were used as Horizontal or Vertical checks only. The results indicate that the VRS network provided positional values within the 5cm parameters for this survey. The survey data was collected using Virtual Reference Stations (VRS) methodology within a Virtual Reference System (VRS). The system is designed to provide a true Network RTK performance, the RTKNet software enables high accuracy positioning in real time across a geographic region. The RTKNet software package uses real time data streams from the GPSNet system user and generates correction models for high accuracy RTK GPS corrections throughout the network. Therefore, corrections were applied to the points as they were being collected, thus negating the need for post process adjustment. After field data is collected the information is downloaded from the data collectors into the office software. The software program used Trimble Business Center (TBC). Downloaded data is run through the Trimble Business Center program to obtain the following reports: points report, point comparison report, and a point detail report. The reports are reviewed for point accuracy and precision. After review of the point data an ASCII or txt file is created. Point files are loaded into Arc Map 10(GIS software) to make a visual check of the point data. Final coordinates are referenced to NAD83 (2011) State Plane Virginia South, US Survey feet and NAVD88 (Geoid12A), US survey feet. Please see the final project report delivered to the USGS for more details. GPS Raw Data 201505 Final Survey Checkpoints Dewberry Consultants LLC mailing and physical address
10003 Derekwood Lane, Suite 204
Lanham MD 20706 USA (301) 364-1855 (301) 731-0188 Monday to Friday, 8 - 5, EST Vector Point 113 Lambert Conformal Conic (State Plane Virginia South FIPS 4502) 36.766 37.966 -78.5 36.333 11482916.666 3280833.333 coordinate pair 0.000100 0.000100 U.S. survey feet North American Datum of 1983(2011) Geodetic Reference System 80 6378137.000000 298.257222 North American Vertical Datum of 1988 (Geoid 12A) 0.000100 US survey feet Explicit elevation coordinate included with horizontal coordinates Survey Checkpoints Surveyor collected points. GPS survey standards FID Internal feature number. Esri Sequential unique whole numbers that are automatically generated. Shape Feature geometry. Esri Coordinates defining the features. PointID Checkpoint name User Defined Name of checkpoint assigined by surveyor. Easting_X X coordinate of checkpoint Surveyor Coordinates defining the features. Northing_Y Y coordinate of checkpoint Surveyor Coordinates defining the features. Z Z or elevation value of checkpoint Surveyor Coordinates defining the features. Type Checkpoint land cover category Surveyor Land cover category U.S. Geological Survey Program Manager mailing and physical address
1400 Independence Road
Rolla MO 65401 USA (573) 308-3810 pemmett@usgs.gov Downloadable Data This data was produced for the U.S. Geological Survey according to specific project requirements. This information is provided "as is". Further documentation of this data can be obtained by contacting: USGS, 1400 Independence Road, Rolla, MO 65401. Telephone (573) 308-3810. 201601 U.S. Geological Survey Patrick Emmett Program Manager mailing and physical address
1400 Independence Road
Rolla MO 65401 USA (573)308-3810 pemmett@usgs.gov FGDC Content Standards for Digital Geospatial Metadata FGDC-STD-001-1998 local time http://www.esri.com/metadata/esriprof80.html ESRI Metadata Profile