U.S. Geological Survey
201502
Unknown
Connecticut_Sandy_Survey_ChkPts
vector digital data
Leading Edge Geomatics collected LiDAR data for approximately 1,526 square miles of area in west-central Connecticut. The nominal pulse spacing for this project was 0.7 meter. Dewberry used proprietary procedures to classify the LAS according to project specifications: 1-Unclassified, 2-Ground, 7-Noise, 9-Water, 10-Ignored Ground due to breakline proximity. Dewberry produced 3D breaklines and combined these with the final LiDAR data to produce seamless hydro flattened Digital Elevation Models (DEMs) with a 1 meter grid cell size that cover the project area. In addition to the bare earth hydro flattened DEMs, Dewberry also produced intensity imagery with a 0.3 meter cell size.
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 1 m cell size hydro flattened Digital Elevation Models (DEMs).
A complete description of this dataset is available in the Final Project Report that was submitted to the U.S. Geological Survey.
20140427
20140529
ground condition
As needed
-72.593
-72.197
41.183
42.049
None
Elevation
Lidar
LAS
DEM
Hydro Flattened
Breaklines
Bare earth
None
Connecticut
Hurricane Sandy
Hartford County
Litchfield County
Fairfield County
New Haven County
New London County
Middlesex County
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) 308-3612.
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 XP Version 5.1 (Build 2600) Service Pack 3; ESRI ArcCatalog 10.0
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 and data passes vertical accuracy specifications.
Survey checkpoint positional values compiled to meet 0.05 meter horizontal accuracy.
0.05
Dewberry Engineers used four existing NGS monuments to check the accuracy of the VRS network. Some of the monuments were used as horizontal control checks. Please see the final project report delivered to the USGS for more details.
In performing the GPS observations, Trimble R-10 GNSS receiver/antenna attached to a 2 meter fixed height pole with a Trimble TSC3 Data Collector to collect GPS raw data were used to perform the field surveys. The 104 Check Points were well distributed throughout the project area so as to cover as many flight lines as possible using dispersed method of placement.
A Ground Control Point Documentation Report sheet was used to show the placement of the nail and a sketch for each of the points surveyed.
The GPS survey performed by Dewberry Engineers Inc. located in Lanham, MD was tied to a Real Time Network (RTN) managed by KeyNetGPS inc. KeyNetGPS is a series of continuously operating, high precision GNSS reference stations. These reference stations have all been linked together using Trimble GPSNet software, creating a Virtual Reference Station System (VRS).
Dewberry Engineers Inc. 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% 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% 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.
Please see the final project report delivered to the USGS for feild observation details.
Four 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 Vertical control checks. Please see the final project report delivered to the USGS for more details.
0.05 m
Based on the vertical accuracy testing conducted by Dewberry, the results indicate that the VRS network is providing positional values within the 5cm parameters for this survey.
Dewberry Engineers Inc. was under contract to provide 104 QA
Check Points for USGS in the state of Connecticut. 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 will complete checkpoint surveys that will be used to evaluate vertical
accuracy on the bare-earth terrain derived from the LiDAR.
Existing NGC Control Points were located and surveyed to check the accuracy of the RTK/GPS survey
equipment with the results shown in section 2.4 of this report.
As an internal QA/QC procedure and to verify that the Check Points meet the 95% confidence level
approximately 50 percent of the points were re-observed.
Final horizontal coordinates are referenced to UTM Zone 18 North, NAD83, in meters. Final Vertical
elevations are referenced to NAVD88, in meters.
Survey Equipment
In performing the GPS observations, Trimble R-10 GNSS receiver/antenna attached to a 2 meter fixed height pole with a Trimble TSC3 Data Collector to collect GPS raw data were used to perform the field surveys.
Survey Point Detail
The 104 Check Points were well distributed throughout the project area so as to cover as many flight lines as possible using dispersed method of placement.
A Ground Control Point Documentation Report sheet was used to show the placement of the nail and a sketch for each of the points surveyed.
Network Design
The GPS survey performed by Dewberry Engineers Inc. located in Lanham, MD was tied to a Real Time Network (RTN) managed by KeyNetGPS inc. KeyNetGPS is a series of continuously operating, high precision GNSS reference stations. These reference stations have all been linked together using Trimble VRS3Net App software, creating a Virtual Reference Station System (VRS).
Field Survey Procedures and Analysis
Dewberry Engineers Inc. 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.
Field GPS observations are detailed on the Ground Control Point Documentation Reports submitted as part of this report.
Ten 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.
Data Processing Procedures
After field data is collected the information is downloaded from the data collectors into the office software. The software programs used Trimble Business Center and Arc Map 10.
Downloaded data is run through the Trimble Business Center program to obtain the following reports; points report, point comparison, 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 to make sure it also checks with the Ground Control Point Documentation Report sketch and description as well as the Pt number, Coordinates, and Elevation.
Please see the final project report delivered to the USGS for more details.
Trimble R-10 GNSS receiver/antenna attached to a 2 meter fixed height pole with a Trimble TSC3 Data Collector to collect GPS raw data.
Inertial Measurement Unit
201405
one hundred and four 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
104
Universal Transverse Mercator
18
0.999600
-75.000000
0.000000
500000.000000
0.000000
coordinate pair
0.000100
0.000100
meters
North American Datum of 1983(2011)
Geodetic Reference System 80
6378137.000000
298.257222
North American Vertical Datum of 1988 (Geoid 12A)
0.000100
meters
Explicit elevation coordinate included with horizontal coordinates
CT_Checkpoints
Surveyor collected points.
RTK GPS survey standards
FID
Internal feature number.
Esri
Sequential unique whole numbers that are automatically generated.
Shape
Feature geometry.
Esri
Coordinates defining the features.
ID
Internal feature number.
Esri
Sequential unique whole numbers that are automatically generated.
PointID
Checkpoint name
Esri
Name of checkpoint assigined by surveyor.
Easting_X
X coordinate of checkpoint in meters
Esri
Coordinates defining the features.
Northing_Y
Y coordinate of checkpoint in meters
Esri
Coordinates defining the features.
Type
Checkpoint land cover category
Esri
Land cover category
Z_Survey
Z value of checkpoint in meters
Esri
Coordinates defining the features.
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) 308-3612.
20150211
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