Geospatial Metadata

Bare Earth Digital Elevation Model (DEM) Generated from LiDAR data of Tile 001 Tenmile & Fifteenmile Creeks, Idaho

Frequently-asked questions:

What does this data set describe?
Who produced the data set?
Why was the data set created?
How was the data set created?
1. Where did the data come from?
2. What changes have been made?
How reliable are the data; what problems remain in the data set?
How can someone get a copy of the data set?
Who wrote the metadata?

What does this data set describe?

Title:

Bare Earth Digital Elevation Model (DEM) Generated from LiDAR data of Tile 001 Tenmile & Fifteenmile Creeks, Idaho

Abstract:

A tin using the Surface Bare Earth LiDAR data was generated in Arc View. A Bare Earth Digital Elevation Model was delivered in ESRI float grid format using a two meter spacing. In a Bare Earth DEM, all canopy and structure information has been subtracted and the result is used to create a DEM of ground elevations.

Horizons, Inc. was contracted by Bureau of Reclamation Boise to provide detailed high-accuracy data for hydraulic analysis and soil classification projects by the Bureau and the NRCS.  The project emcompassed an area of approximately 150 square miles.  LiDAR acquisition was obtained on December 9, 2003 at 8000' AMT by subcontractor EarthData Aviation. The Navajo Chieftain (tail number N62912) was equipped with an LH System ALS40 LiDAR system including an inertial measuring unit (IMU) and a dual frequency airborne GPS receiver.  LiDAR data was collected with a 2.0 to 2.2 meter nominal post spacing, 25 percent field of view and a 30 percent overlap. Ground control survey was conducted by subcontractor DJ&A of Missoula, MT. LiDAR data processing included processing of the raw LiDAR data through a minimum block algorithm to classify points as bare-earth or non-bare earth. Points were edited in 2D using imagery, intensity of the LiDAR reflection and tin-editing software to ensure accuracy of the automated feature classification. Final delivery included Acquisition/Processing Report, Flight Map, Raw LiDAR data, Intensity Image, Bare Earth DEM and First Return DEM.

Supplemental information:

The raw LIDAR point files were delivered in a proprietary binary format along with an ASCII translator.  The point files were delivered to the project boundary and tiled into approximately 1 million point files.  Each point contained Ground X -- Easting or "X" value for each LIDAR point; Ground Y -- Northing or "Y" value for each LIDAR point; Ground Z -- Elevation or "Z" value for each LIDAR point; Plane X -- Easting or "X" value for the aircraft at the time the point was fired ;Plane Y -- Northing or "Y" value for the aircraft at the time the point was fired; Plane Z -- Elevation or "Z" value for the aircraft at the time the point was fired; GPS Time -- GPS Time that the pulse was received; Scan Angle -- Angle of the scanner mirror at the time the instrument was fired; Roll Angle -- Roll (Omega) angle of the aircraft at the time the instrument was fired; Pitch Angle -- Pitch (Phi) angle of the aircraft at the time the instrument was fired; Heading Angle -- Heading (Kappa) angle of the aircraft at the time the instrument was fired; Intensity -- Intensity of the reflective surface based on amount of pulse returned; AGC Value -- Automatic Gain Control setting (Iris opening value) based on intensity of past returns; Return Number -- Value for the sequence for which a return was detected from a single pulse; GPS Week -- GPS week designation for the time of data acquisition; Classification -- Description given to each point based on the surface that reflected the pulse; Point Layer -- Point layer further describes the relationship of returns within a single laser a point with a return number of (1) could be further classified as "First and Only" or "First of Many"; Geoid Height -- Elevation difference between the ellipsoid and geoid heights. First Return Digital Elevation A tin using the Raw first return LIDAR data was generated in ArcView.  A First Return Digital Elevation Model was delivered in ESRI float grid format using a two A tin using the Surface Bare Earth LiDAR data was generated in Arc View. A Bare Earth Digital Elevation Model was delivered in ESRI float grid format using a two meter During LiDAR acquistion an 8 bit intensity or surface reflectivity value is collected for each LiDAR point with a value ranging from 0 to 255.  An image of the reflectivity surface was produced by generating a raster grid over the raw first return points and giving each pixel a value equal to the average of the LIDAR point intensity values that fell within it.  A nearest neighbor interpolation was performed to give empty cells intensity values.  A geotiff format black and white image of the LIDAR reflective surface was the resultant product. All project deliverables were submitted in two coordinate systems - UTM and IDTM (specifics described above). The projection of the project boundary from UTM to IDTM (or vice versa) introduces a slight rotation. A tile layout for each projection system was developed to ensure tile layouts in a north-south and east-west format.  Each tile was sized to be 4572 meters x Tiles were named the same in both projection systems but, due to the projection rotation, will not cover the same area within the project boundary and will not contain the same number of raw LIDAR points.)

How should this data set be cited?

Horizons, Inc., 20040528, Bare Earth Digital Elevation Model (DEM) Generated from LiDAR data of Tile 001 Tenmile & Fifteenmile Creeks, Idaho: Bureau of Reclamation, Snake River Area Office, Boise, ID, USA.
Online links:
- http://insideidaho.org/data/BOR/archive/UTM/LiDARbedem_tile001_bor_utm1183.tgz
- http://insideidaho.org/geodata/LiDAR/index.htm
What geographic area does the data set cover?

Bounding coordinates:

West: -116.278728

East: -116.227944

North: 43.477965

South: 43.463679
What does it look like?

Thumbnail image:
Does the data set describe conditions during a particular time period?

Calendar date: 20031209

Currentness reference:
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ground condition
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What is the general form of this data set?

Geospatial data presentation form: raster digital data
How does the data set represent geographic features?
1. How are geographic features stored in the data set?
  This is a Raster data set. It contains the following raster data types:
  - Dimensions 775 x 2047 x 1, type Grid Cell
2. What coordinate system is used to represent geographic features?
  
  The grid coordinate system used is Universal Transverse Mercator
  
  Universal Transverse Mercator
  
  UTM zone number: 11
  
  Transverse Mercator projection parameters:
  
  Scale factor at central meridian: 0.999600
  
  Longitude of central meridian: -117.000000
  
  Latitude of projection origin: 0.000000
  
  False easting: 500000.000000
  
  False northing: 0.000000
  
  Planar coordinates are encoded using row and column.
  
  Abscissae (x-coordinates) are specified to the nearest 2.000000.
  
  Ordinates (y-coordinates) are specified to the nearest 2.000000.
  
  Planar coordinates are specified in meters.
  
  The horizontal datum used is North American Datum of 1983.
  
  The ellipsoid used is Geodetic Reference System 80.
  
  The semi-major axis of the ellipsoid used is 6378137.000000.
  
  The flattening of the ellipsoid used is 1/298.257222.

How does the data set describe geographic features?

Entity and attribute overview:

Bare Earth Digital Elevation Model. A tin using the Surface Bare Earth LiDAR data was generated in Arc View. A Bare Earth Digital Elevation Model was delivered in ESRI float grid format using a two meter spacing.

Note Regarding Data Tiling. All project deliverables were submitted in two coordinate systems - UTM and IDTM (specifics described above). The projection of the project boundary from UTM to IDTM (or vice versa) introduces a slight rotation. A tile layout for each projection system was developed to ensure tile layouts in a north-south and east-west format.  Each tile was sized to be 4572 meters x 4572 meters. Tiles were named the same in both projection systems but, due to the projection rotation, will not cover the same area within the project boundary and will not contain the same number of raw LIDAR points.

Entity and attribute detail citation:

None

Who produced the data set?

Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
- Horizons, Inc.
Who also contributed to the data set?
To whom should users address questions about the data?
Roger Hirschman

USDA, Natural Resource Conservation Service

GIS Specialist
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9173 West Barnes Drive, Suite C
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Boise, Idaho 83709-1574

United States

208-378-5785 (voice)

Roger.Hirschman@id.usda.gov

Hours of Service: 8am-5pm Mountain Time

Why was the data set created?

The data will be used to provide high-accuracy data for hydraulic analysis and soil classification projects.

How was the data set created?

Where did the data come from?
None (source 1 of 1)

Horizons, Inc., 20030528, 10-15 Mile Creek, Idaho.

Type of source media: none

Source scale denominator: 8000 amt

Source contribution:
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None
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What changes have been made?

Date: 20040609 (change 1 of 1)

AeroScan LiDAR timed reflection data and the IMU SBET files were processed together using LiDAR processing software. The data set for each flight line was checked for data gaps between overlapping flightlines, and tension/compression areas (areas where data points are more or less dense that the average project specified post spacing). LiDAR data was collected for bi- and cross-directional flight lines over an airport prior to acquisition of the project area. Comparative analysis of the data produced a preliminary omega,phi,kappa correction. LiDAR data was processed and evaluated until angles met project specifications. All flight lines (airport and project) were checked and verified for vertical accuracy of 15 cm. An intensity raster for each flight line was generated and verified that intensity was recorded for each LiDAR point. Static survey ground control points at the airport were compared to the LiDAR data set and the LiDAR data was vertically biased down to the ground. Lidar data in overlap areas of project flight lines was removed. The raw LiDAR data set was processed through a minimum block mean algorithm and points were classified as either bare earth or non-bare earth. User developed macros that factor mean terrain angle and height from the ground were used to determine bare earth point classification. A 2D edit (surfacing) process ensures the accuracy of the automated feature classification. Imagery, intensity of the LiDAR reflection and tin-editing software were combined to assess points.

Person responsible for change:

Mary Bosworth

Horizons Inc.

Project Manager

3600 Jet Drive

Rapid City, South Dakota 57703

United States

605-343-0280 (voice)

605-343-0305 (FAX)

bosworth@horizonsinc.com

Hours of Service: 8am-5pm Mountain Time

Data sources used in this process:

None

Data sources produced in this process:

None

How reliable are the data; what problems remain in the data set?

How well have the observations been checked?

All GPS phase data was post processed with continuous kinematic survey techniques using "On the Fly" (OTF) integer ambiguity resolution. The GPS data was processed with forward and reverse processing algorithms. The results from each process, using the data collected at the airport, were combined to yield a single fixed integer phase differential solution of the aircraft trajectory. Plots of altitude and the forward and reverse GPS solution residuals are attached. In the portion of the flight over the project area, the small differences between the trajectories of the forward and reverse solutions (less than +/- 3 cm in the horizontal and less than +/- 5 cm in the vertical) indicate a valid solution with ambiguities correctly fixed to integer values.

Extensive comparisons were made of vertical and horizontal positional differences between points common to two or more LiDAR flight lines. This was done for the airport bore-site testing area and the project area. All comparisons were found to be well within project specifications. Vertical Bias Correction. LiDAR ground points were compared to independently surveyed and positioned ground points at both the airport bore-sight area and the project area. Comparisons to the project control points as well as the airport points indicated a vertical bias of 41.5 cm. All LiDAR points were lowered by this amount.

Comparisons to on-site control points yielded the following
09 December 2003
Vertical Accuracy 3.2 cm RMSE
Standard Deviation 3.1 cm
Mean Difference 1.2 cm
Number of Points in Sample 11

The comparison with the kinematic survey at the airport
09 December 2003
Vertical Accuracy 5.9 cm RMSE
Standard Deviation 3.4 cm
Mean Difference 4.9 cm
Number of Points in Sample 84

How accurate are the geographic locations?

The estimated horizontal error for nadir and FOV edge is 0.23 meters.

How accurate are the heights or depths?
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3.2cm Z - RMS
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Where are the gaps in the data? What is missing?
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None
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How consistent are the relationships among the observations, including topology?
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None
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How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access constraints: None

Use constraints:

None

Distributor 1 of 2 <Next>

Who distributes the data set?

Bruce Godfrey

Idaho Geospatial Data Clearinghouse

GIS Specialist

Box 442350

Moscow, ID 83844-2350

USA

208.885.6463 (voice)

bgodfrey@uidaho.edu

What's the catalog number I need to order this data set?

Downloadable Data

What legal disclaimers am I supposed to read?

Although these data have been processed successfully on a computer system at the University of Idaho Library, no warranty, expressed or implied, is made regarding the utility of the data on any other system, nor shall the act of distribution constitute any such warranty.

How can I download or order the data?

Availability in digital form:

Data format:	in format ESRI GRID Size: 6.087
Network links:	http://insideidaho.org/data/BOR/archive/UTM/LiDARbedem_tile001_bor_utm1183.tgz
Media you can order:	DVD(Density 4700megabytes) (format UDF)