LiDAR Deliverables for GIS Users

Isaiah DitmerLiDAR AnalystAKSMC February 2013

AeroMetric Company Overview

Geospatial Services Provider Historical Imagery

LiDAR

Photogrammetry

Satellite Imagery

Enterprise GIS

Notable Markets Include Large Scale Mapping

Airport Obstruction Surveys

Forestry & Environmental Studies

Transportation & Utility Mapping

Emergency Management

dy·nam·ic (adj.) \dī- na-mik\ ˈ

marked by usually continuous and productive activity or change

The State of Alaska is dynamic

The Alaskan GIS Community is dynamic

LiDAR as a Geospatial tool is dynamic

Sounds like we’re in good company!

AKSMC 2013

Today’s Underlying Theme…

LiDAR Products & UsesAn Overview

Digital Elevation Models & Contours

Most Common LiDAR Deliverables

Generated from “Bare-Earth” classified LiDAR data and digitized breaklines

Innumerable uses, from infrastructure to hydrological analysis

Often used to generate other terrain-based GIS data sets such as aspect and slope rasters

AKSMC 2013

River Valley DEM & ContoursHydro-flattened LiDAR data along Willow Fishook Road West of Hatcher’s Pass

Mountainous DEMModels such as this are frequently used throughout Alaska for applications such as line-of-sight analysis and route planning

AKSMC 2013

DTM Resolution Comparisons

Digital Surface Models

Generated from First-Return LiDAR data in order to represent continuous surface as viewed from above

Used to analyze relationship between terrain and natural or man-made obstructions above it

Especially convenient for raster analysis

AKSMC 2013

Seward, Alaska DSMModel includes tree canopy as well as man made structures.

Seward, Alaska DEMBare-Earth model of terrain that could be used to analyze feature heights etc. from DSM

LAS Point Cloud Data

LAS Data is inherently attribute rich Each file consists of a Header, Variable Length

Records (VLRs), and Point Records

While ground / non-ground is the base classification, endless options abound

New LiDAR tools in ArcGIS 10.1 increase accessibility for end users to this richness

AKSMC 2013

Fully Classified LAS DataUnique point classes used for structures, transmission lines, and vegetation, in addition to the bare-earth terrain

LiDAR Standards & SpecsA Brief Overview

Data Resolution

LiDAR data resolution referred to as either “Nominal Point Spacing” (NPS) or Point Density (in terms of points per square meter)

Related as follows:

USGS Base Specification Calls for an NPS of 2 meters or less (or a density of at least 0.25 ppm^2)

High accuracy airborne LiDAR typically requires densities of 6 – 10 ppm^2

AKSMC 2013

density

1NPS

Vertical Accuracy

Determined through comparisons with surveyed ground data

The Fundamental Vertical Accuracy (FVA) of a LiDAR data set is reported as RMSEz * 1.960, which gives the NSSDA 95% confidence interval

Supplemental Vertical Accuracy (SVA) checks in categories other than “open terrain” may be desired and /or required

AKSMC 2013

Hydro-Flattening

USGS Base Specification requires lakes at single elevations, rivers flat bank-to-bank and following gradient of surrounding terrain.

Breaklines to be digitized for lakes of 2 acres or greater surface area, rivers of 100 feet or greater nominal width

Goal is for DEMs to represent water bodies in a “cartographically and aesthetically pleasing manner.”

AKSMC 2013

Hydro-Flattened Water BodiesHere the flattened wireframe is shown illustrating how software flattens lakes using breaklines

AKSMC 2013

Hydro Enforcement Comparison

LiDAR ProcurementAll Things Considered

A Good Starting Point…

Before ironing out the details of a Scope of Work, consider the following questions, and discuss them with a LiDAR consultant if possible:

What will this data be used for ultimately?

Who will ultimately be using this data?

Will this data need to tie into existing data sets?

What products will be derived from this data set?

AKSMC 2013

Product Considerations

What resolution of data do you need? Are additional/ unique classifications desired?

Is hydro-flattening or hydro-enforcement required? USGS or custom tailored specifications?

Is vertical accuracy a concern? Is vertical accuracy in additional land cover categories a concern?

Further questions? Get in touch!

AKSMC 2013

Relevant Sources:USGS LiDAR Base Specification v 1.0http://pubs.usgs.gov/tm/11b4/

ASPRS Guidelines Vertical Accuracy

Reporting www.asprs.org/a/society/committees/lidar/Downloads/Vertical_ Accuracy_Reporting_for_Lidar_Data.pdf

AeroMetric

AeroMetric

Aero-Metric, Inc.

www.aerometric.co

m