SWFWMD LiDAR Specifications – 18 April 2008 LiDAR Specifications at the SWFWMD Ekaterina Fitos &...

SWFWMD LiDAR Specifications – 18 April 2008

LiDAR Specifications at the SWFWMD

Ekaterina Fitos & Al Karlin


What is LiDAR?

LiDAR is an acronym for

Light Detection and Ranging

LiDAR can:

Measure DistanceMeasure SpeedMeasure RotationMeasure Chemical Composition

(and Concentration)


Common LiDAR Detectors


Pulse A – Hits the ground unobstructed;

First and Last return(s) are the same;Single return

Pulse B – Encounters several obstacles on the

way to the ground;Multiple returns, last return is

Interpreted as ground.

Possible LiDAR Returns


LiDAR Image using ALL ReturnsLiDAR Image using ONLY Last Returns


LiDAR Deliverables and Formats


Typical Software used with LiDAR Data

http://www.prospatial.com/lp360.html

http://www.esri.com/software/arcgis/index.html

http://www.terrasolid.fi/en


Some “ACCURACY” definations:


Some “TYPICAL” LiDAR Accuracies


LiDAR Information Sources

USGS Center for LiDAR Information Coordination

And Knowledge

http://lidar.cr.usgs.gov/


International LiDAR Mapping Forum

LiDAR Information Sources

http://www.lidarmap.org/


LiDAR Project Specifications

• The District has actively been collecting LiDAR since 2003.

• LiDAR at the District is commonly coupled with Aerial Imagery acquisitionto ensure accurate collection of breaklines,and cost savings.

• Intended Uses of LiDAR– Supports Regulatory, land acquisition, planning,

engineering, and restoration projects.– Commonly used for Water Management Plans.– Digital Flood Insurance Rate Maps (DFIRM) Updates.


• Two common formats of LiDAR Datasets:– ASCII XYZ and TIN Generate Files pre-2005– LAS and Breaklines (Shapefiles or Feature

Classes) post-2004

• Tiled by:– STR pre-2005– 5,000’ by 5,000’ Statewide Tiling System

post-2004

• District is Currently Re-tiling LiDAR Datasets and File Formats to be LAS and Feature Classes.

LiDAR Project Specifications Con’t


• LiDAR Acquisition– Flight Window January 1st to March 31st

– Optimal Weather Conditions for Florida• Lower Humidity• Less Cloud Cover• Decreased Precipitation• Leaf-Off

• Projection– Florida State Plane West (US Feet)

• Horizontal and Vertical Datum– North American Datum of 1983/NSRS2007– North American Vertical Datum of 1988 (NAVD 88)



• LiDAR Accuracies

– Vertical Accuracy Tested to Meet 0.6-Feet Fundamental Accuracy at 95% CI using RMSE(z) * 1.96 According to National Standard for Spatial Data Accuracy (NSSDA).

• 30 Ground Measurements Per Urban, Bare Ground/Short Grass, Brush, and Forest to Test Against LiDAR Surface to Assess Vertical Accuracy.

– Horizontal Accuracy Meet or Exceed 7.6-Feet at a 95% CI using RMSE(r) x 1.7308 Defined by FGDC Geospatial Positioning Accuracy Standards

• Difficult to Ascertain



• LiDAR Dataset Format Classification– After 2004 Required Delivery of LiDAR Full Point Cloud – LAS Format 1.0 or 1.1– Average Nominal Point Spacing of 4-Feet post-2004; 6-Feet pre-2004

– Point Cloud Classified into 1 of 5 Classes:o Class 1- Unclassified (Noise, Vegetation, Buildings)o Class 2 – Groundo Class 9 – Watero Class 10 – Photogrammetrically Placed Ground Elevations

(Points NOT Collected by the LiDAR Sensor in Areas Where Insufficient LiDAR Coverage Occurred.)

o Class 11 – Wetland/Swamps



CAUTION:

When Using Class 11 these Wetland/Swamp Areas May Have Artificial Lower Returns due to Hydric Soils.



• Breaklines– Must be Used with LiDAR to Create a

Hydrologically Correct Model

– 8 Feature Types

o Closed Terrestrial Waterbodieso Linear Hydrographic Featureso Islandso Roadso Soft Breaklineso Low Confidence Areas (Formerly Obscured Areas)o Over Passes/Bridgeso Coastal Shorelines



• Breaklineso Closed Terrestrial Waterbodies: > Half Acreo Linear Hydrographic Features:

> Half-Mile in Length; < 8-Feet Wide Single Breakline; > 8-Feet Wide Double Breakline

o Islands: > Half Acre

Where Necessary Delineate o Roadso Soft Breaklineso Low Confidence Areas (Formerly Obscured Areas)o Over Passes/Bridges



• For Elevation Models Utilize o Class 2o Class 10 o Class 11

• Incorporate Breaklines with Masspoints.

• Commonly Use 5 Breakline Types– Roads – Islands – Closed Waterbodies – Linear Hydrographic Features– Soft Breaklines



• Contours– 1-Foot Intervals at a 2-Foot Specification– +/- 1-Foot Accuracy– Derived Surface– Primary Purpose: Visualization

– In Depth Modeling Requires Utilizing Source Data:

• LAS • Breaklines



• All Projects Require Metadata and Survey Reports

• Survey Reports Require Certifcation by a Professional Surveryor and Mapper.



Contact Information: (e-mail @SWFWMD.State.FL.US)

Al Karlin (x4204)Ekaterina Fitos (x4219)Lela Clark (x4278)

http://ftp.swfwmd.state.fl.us/pub/GWIS

Questions? Comments? Suggestions?

SWFWMD LiDAR Specifications – 18 April 2008 LiDAR Specifications at the SWFWMD Ekaterina Fitos &...

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