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OCM Partners, 2024: 2003 Puget Sound LiDAR Consortium (PSLC) Topographic LiDAR: Snohomish County, Washington,

Item Identification

Title: 2003 Puget Sound LiDAR Consortium (PSLC) Topographic LiDAR: Snohomish County, Washington
Short Name: wa2003_pslc_snohomish_m1462_metadata
Status: Completed
Publication Date: 2013-03

TerraPoint surveyed and created this data for the Puget Sound LiDAR Consortium under contract. The area surveyed is approximately 167 square miles and covers a northwest portion of Snohomish County, WA.

All data was collected during ideal conditions (leaf-off).

The LAS files were derived from all returns ASCII files contain the X,Y,Z values of all the LiDAR returns collected during the survey mission. The GPS time, classification, scan angle, intensity and return numbers of each point

were preserved in the conversion from ASCII to LAS. The LAS files are classified into the following ASPRS classes: (1) Unclassified (2) Bare Earth. Ground and water points are included in Class 2 (Bare Earth). Futher details are

available in the Process Steps below. The NOAA Office for Coastal Management noticed that some intensity values are 0, so be aware before using the intensity information.

This dataset was flown in 2003 with a 50% overlap between flight lines. Due to the overlap the nominal point spacing of the dataset is 1.0 meter.


The LAS files can be used to create DEMs and also to extract topographic data in software that does not support raster data. Other surface features can also be extracted with custom applications. This high accuracy data can

be used at scales up to 1:12000 (1 inch = 1,000 feet). LiDAR data has a wide range of uses such as earthquake hazard studies, hydrologic modeling, forestry, coastal engineering, roadway and pipeline engineering, flood plain

mapping, wetland studies, geologic studies and a variety of analytical and cartographic projects.



Supplemental Information:

A footprint of this data set may be viewed in Google Earth at:


Theme Keywords

Thesaurus Keyword
ISO 19115 Topic Category

Physical Location

Organization: Office for Coastal Management
City: Charleston
State/Province: SC

Data Set Information

Data Set Scope Code: Data Set
Maintenance Frequency: As Needed
Data Presentation Form: las
Entity Attribute Overview:

LiDAR points in LAS 1.2 format

Entity Attribute Detail Citation:


Distribution Liability:

Any conclusions drawn from the analysis of this information are not the responsibility

of Terrapoint, PSLC, NASA, USGS, NOAA, the Office for Coastal Management or its partners.

Data Set Credit: Please credit the Puget Sound LiDAR Consortium (PSLC) for these data. The PSLC is supported by the Puget Sound Regional Council, the National Aeronautical and Space Administration (NASA), the United States Geological Survey (USGS) and numerous partners in local, state, and tribal government.

Support Roles

Data Steward

CC ID: 692068
Date Effective From: 2013-03
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202


CC ID: 692070
Date Effective From: 2013-03
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202

Metadata Contact

CC ID: 692071
Date Effective From: 2013-03
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202

Point of Contact

CC ID: 692069
Date Effective From: 2013-03
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202


Currentness Reference: Ground Condition

Extent Group 1

Extent Group 1 / Geographic Area 1

CC ID: 1133538
W° Bound: -122.409833
E° Bound: -122.175578
N° Bound: 48.300496
S° Bound: 48.025012

Extent Group 1 / Time Frame 1

CC ID: 1133537
Time Frame Type: Range
Start: 2003-04-02
End: 2003-04-12

Spatial Information

Spatial Representation

Representations Used

Vector: Yes

Access Information

Security Class: Unclassified
Data Access Procedure:

This data can be obtained on-line at the following URL:


Data Access Constraints:


Data Use Constraints:

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. These data

depict the heights at the time of the survey and are only accurate for that time.

Distribution Information

Distribution 1

CC ID: 743264
Download URL:
File Name: Customized Download

Create custom data files by choosing data area, product type, map projection, file format, datum, etc.

Distribution 2

CC ID: 743265
Download URL:
File Name: Bulk Download

Simple download of data files.



CC ID: 743267
URL Type:
Online Resource


CC ID: 743268
URL Type:
Online Resource


CC ID: 743269
Name: Browse Graphic
URL Type:
Browse Graphic
File Resource Format: kmz

This graphic shows the lidar coverage for a section of Snohomish County in Washington.

Activity Log

Activity Log 1

CC ID: 692087
Activity Date/Time: 2016-05-23

Date that the source FGDC record was last modified.

Activity Log 2

CC ID: 692086
Activity Date/Time: 2017-11-14

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using '' script. Contact Tyler Christensen (NOS) for details.

Activity Log 3

CC ID: 718747
Activity Date/Time: 2018-02-08

Partial upload of Positional Accuracy fields only.

Activity Log 4

CC ID: 743266
Activity Date/Time: 2018-03-13

Partial upload to move data access links to Distribution Info.

Data Quality


Elevations are recorded in floating-point meters and the vertical datum is ellipsoidal (GEOID99). There are no other attribute tables.

Horizontal Positional Accuracy:

Not applicable for pure elevation data: every XY error has an associated Z error.

Vertical Positional Accuracy:

Puget Sound Lidar Consortium evaluates vertical accuracy with two measures: internal consistency and conformance with independent ground control points.

Internal Consistency: Data are split into swaths (separate flightlines), a separate surface is constructed for each flightline, and where surfaces overlap one is subtracted from another. Where both surfaces are planar,

this produces a robust measure of the repeatability, or internal consistency, of the survey. The average error calculated by this means, robustly determined from a very large sample, should be a lower bound on the true

error of the survey as it doesn't include errors deriving from a number of sources including: 1) inaccurately located base station(s), 2) long-period GPS error, 3) errors in classification of points as ground and not-ground

(post-processing), 4) some errors related to interpolation from scattered points to a continous surface (surface generation).

Conformance with independent ground control points: Bare-earth surface models are compared to independently-surveyed ground control points (GCPs) where such GCPs are available. The purpose of the ground control evaluation

is to assess that the bare earth DEMs meet the vertical accuracy specification in the PSLC contract with TerraPoint:

"The accuracy specification in the contract between the Puget Sound LiDAR Consortium and TerraPoint is based on a required Root Mean Square Error (RMSE) 'Bare Earth' vertical accuracy of 30 cm for flat areas in the complete

data set. This is the required result if all data points in flat areas were evaluated. Because only a small sample of points is evaluated, the required RMSE for the sample set is adjusted downward per the following equation

from the FEMA LiDAR specification (adjusted from the 15 cm RMSE in the FEMA specification to 30 cm to accommodate the dense vegetation cover in the Pacific Northwest)."

During this step, the bare earth DEMs were compared with existing survey benchmarks. The differences between the LiDAR bare earth DEMs and the survey points are calculated and the final results are first summarized in a graph

that illustrates how the dataset behaves as whole. The graph illustrates how close the DEM elevation values were to the ground control points. The individual results were aggregated and used in the RMSE calculations. The results

of the RMSE calculations are the measure that makes the data acceptable for this particular specification in the contract.

; Quantitative Value: 0.30 meters, Test that produced the value:

Root mean square Z error in open, near-horizontal areas, as specified by contract. Units in meters. Our assessment suggests that all data meet this standard. Accuracy may be significantly less in steep areas and under heavy forest canopy.

Accuracy appears to be significantly better for data acquired in early 2003 and afterward, to which in-situ calibration has been applied.

Completeness Report:

Elevation data has been collected for all areas inside project boundaries.

Conceptual Consistency:

Puget Sound Lidar Consortium evaluates logical consistency of high-resolution lidar elevation data with three tests: examination of file names, file formats, and mean and extreme values within each file; internal consistency of

measured Z values in areas where survey swaths overlap; and visual inspection of shaded-relief images calculated from bare-earth models. File names, formats, and values: All file naming convention and file formats are check for


Internal Consistency Analysis: This analysis calculates and displays the internal consistency of tiled multi-swath (many-epoch) LiDAR data. The input for this analysis is the All-return ASCII data, but it only uses the first

returns. The data is divided into swaths, or flightlines, and they are compared with each other. Since the contract specifications require 50% sidelaps, it means that all areas should have been flown twice. The results of

this analysis is to verify that the data was generally flown to obtain the 50% sidelaps, that there are no gaps between flightlines and also that overlapping flightlines are consistent in elevation values.

Visual inspection of shaded-relief images: During the visual inspection, hillshades are derived from the bare earth DEMs. The hillshades are examined for any obvious data errors such as blunders, border artifacts, gaps between

data quads, no-data gaps between flight lines, hillscarps, land shifting due to GPS time errors, etc. The data is examined a scale range of 1:4000 to 1:6000. During this process we also compare the data to existing natural features

such as lakes and rivers and also to existing infrastructure such as roads. Orthophotos area also used during this phase to confirm data errors. If any of these data errors are found, they are reported to TerraPoint for correction.


Process Steps

Process Step 1

CC ID: 1133532


Lidar data were collected in leaf-off conditions (approximately 1 November - 1 April) from a fixed-wing aircraft flying at a nominal height of 1,000 meters above ground surface. Aircraft position was monitored by

differential GPS, using a ground station tied into the local geodetic framework. Aircraft orientation was monitored by an inertial measurement unit. Scan angle and distance to target were measured with a scanning

laser rangefinder. Scanning was via a rotating 12-facet pyramidal mirror; the laser was pulsed at 30+ KHz, and for most missions the laser was defocussed to illuminate a 0.9m-diameter spot on the ground. The rangefinder

recorded up to 4 returns per pulse. Flying height and airspeed were chosen to result in on-ground pulse spacing of about 1.5 m in the along-swath and across-swath directions. Most areas were covered by two swaths, resulting

in a nominal pulse density of about 1 per square meter.

Process Step 2

CC ID: 1133533


GPS, IMU, and rangefinder data were processed to obtain XYZ coordinates of surveyed points.

For data acquired after January 2003 (NW Snohomish, Mt Rainier, Darrington, and central Pierce projects), survey data from areas of swath overlap were analysed to obtain best-fit in-situ calibration parameters that

minimize misfit between overlapping swaths. This reduces vertical inconsistency between overlapping swaths by about one-half.

Heights were translated from ellipsoidal to orthometric (NAVD88) datums via GEOID99

Process Step 3

CC ID: 1133534

ASCII file generation

All Point returns with all their attributes were directly exported into ASCII files. These were first divided into USGS quarter quads (3.25 minute by 3.25 minute) and then in 25 tiles per quarter quad.

Process Step 4

CC ID: 1133535

The NOAA Office for Coastal Management (OCM) received topographic files in ASCII .TXT format. The files contained lidar

elevation measurements. The data were received in Washington State Plane North Zone 4601, NAD83 coordinates

and were vertically referenced to NAVD88 using the Geoid99 model. The vertical units of the data were

feet. OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. The ASCII .TXT files were parsed and converted to LAS version 1.2 using LAStools' txt2las tool.

2. Bad elevations were filtered and removed from many tiles across the data set on a tile by tile basis using LASTools' las2las tool.

3. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid99.

4. The topographic las files were converted from a Projected Coordinate System (WA SP North) to a Geographic Coordinate system (NAD 83).

5. The topographic las files' vertical units were converted from feet to meters.

6. The topographic las files' horizontal units were converted from feet to decimal degrees.

Process Date/Time: 2013-02-01 00:00:00

Catalog Details

Catalog Item ID: 50142
GUID: gov.noaa.nmfs.inport:50142
Metadata Record Created By: Anne Ball
Metadata Record Created: 2017-11-15 15:24+0000
Metadata Record Last Modified By: SysAdmin InPortAdmin
Metadata Record Last Modified: 2022-08-09 17:11+0000
Metadata Record Published: 2022-03-16
Owner Org: OCMP
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2022-03-16
Metadata Review Frequency: 1 Year
Metadata Next Review Date: 2023-03-16