Transcript
Page 1: Lidar and the Oregon Lidar Consortium

Lidar and the Oregon Lidar Lidar and the Oregon Lidar ConsortiumConsortium

Portland State Office Building:

photo and lidar point cloud

Beaverton: photo and lidar highest hit model

Eagle Creek landslides, abandoned railroad: photo and

bare earth model

Page 2: Lidar and the Oregon Lidar Consortium

What is lidar (light detection and ranging)?What is lidar (light detection and ranging)?- Simply making lots of accurate distance - Simply making lots of accurate distance measurements with a laser rangefinder.measurements with a laser rangefinder.

Accurate laser rangefinders are commonly used as surveying instruments, measuring tapes, rifle scopes, even golf aids! Distance is calculated

by measuring the time that a laser pulse takes to travel to and from an object.

Page 3: Lidar and the Oregon Lidar Consortium

Millions of very precise laser range measurements are Millions of very precise laser range measurements are made made

from a precisely located aircraft, producing an accurate from a precisely located aircraft, producing an accurate and detailed 3-D map of the earth’s surface, as a “point and detailed 3-D map of the earth’s surface, as a “point

cloud.”cloud.”On-ground RTK-GPS base stations broadcast corrections to airborne GPS unit, locating the aircraft with an accuracy of a few centimeters.

Aircraft attitude is precisely measured by Inertial Motion Unit, so that the exact position and orientation of the laser rangefinder is always known.

The rangefinder scans across the surface at 100,000 to 200,000 pulses per second, collecting millions or billions of precise distance measurements, which are converted to 3-D coordinates.

Page 4: Lidar and the Oregon Lidar Consortium

Point cloud data define the 3-D shape and location

of the land, vegetation, and structures.

(above) Animated point cloud image of the Portland LDS Temple; points are colored by their relative height: red highest, blue lowest.

(right) Photo of the same building; note statue on left hand spire, visible in both images.

The complete collection of measured points for an area is called the point cloud, which is the fundamental form of lidar data. It provides a very detailed and accurate 3-D map of ground surface, vegetation, and structures.

Page 5: Lidar and the Oregon Lidar Consortium

Each laser pulse can produce multiple consecutive Each laser pulse can produce multiple consecutive measurements from reflections off several surfaces in its measurements from reflections off several surfaces in its

path.path.

• red= 1st return

• yellow = 2nd return

• green = 3rd return

This provides detailed images of vegetation structure and density, and returns data from the ground under tree cover.

Image on the left is a point cloud lidar view of the tree in the photo on the right. Each point is colored by which return it was from a particular pulse:

Page 6: Lidar and the Oregon Lidar Consortium

OLC data are collected at very high pulse density, OLC data are collected at very high pulse density, producing very detailed images.producing very detailed images.

Point cloud image on left compared to orthophoto on right shows actual point density of lidar data acquired over school bus lot. Each bus has been measured by 180-200 lidar points!

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The lidar point cloud can even image livestock The lidar point cloud can even image livestock in the field!in the field!

Red and yellow clusters of points above ground are Red and yellow clusters of points above ground are cattle standing or lying in pasture.cattle standing or lying in pasture.

Page 8: Lidar and the Oregon Lidar Consortium

Very high point density means that even in heavily forested areas, it is Very high point density means that even in heavily forested areas, it is still possible to get a large number of measurements of the ground. still possible to get a large number of measurements of the ground. Left image is orthophoto of the Tualatin River, right image is lidar Left image is orthophoto of the Tualatin River, right image is lidar point cloud with point cloud with red points high, blue points low. red points high, blue points low.

The lidar vendor uses a variety of software filters to choose the points out of the point cloud that measure the ground surface. In the image on the right, vegetation points are green and ground points yellow. Even in thick forest there are numerous ground points.

Even if only one point in one hundred is a ground point, the huge number of points means that a smooth seamless ground model can be made. The image on the left is a bare earth digital elevation model, with 3 ft pixels, and reveals incredible detail of the terrain beneath the trees, including a hidden landslide.

For comparison, the best previously available ground model is shown on the left. The 10-m USGS Digital Elevation Model shows only a crude representation of the real surface.

Page 9: Lidar and the Oregon Lidar Consortium

Bare earth lidar can show features that Bare earth lidar can show features that you cannot even see on the ground.you cannot even see on the ground.

Perspective view of lidar (Dec. 2007) on left matches photograph

(July 2008) on right. The lidar was flown before clear cut logging of the reddish-brown slope, yet clearly shows an old logging road that is barely visible in the

photograph.

Arrows connect matching locations.

Page 10: Lidar and the Oregon Lidar Consortium

Lidar intensity image with 1 ft pixels

Additional standard lidar products include a “highest hit” Additional standard lidar products include a “highest hit” or “first returns” model, which shows the tops of trees or “first returns” model, which shows the tops of trees

and buildings, and buildings, and an intensity image, which is a form of infrared and an intensity image, which is a form of infrared

photograph.photograph.True color orthophoto with 0.5 ft pixels Lidar highest hit model with 3 ft pixels

Transmission lines

Nursery stock

Quarry

Residence

Auto

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Lidar data allow a wide variety of information about Lidar data allow a wide variety of information about forests to be measured with unprecedented accuracy forests to be measured with unprecedented accuracy

and completeness.and completeness.

• Locate and measure individual trees in forest

• Estimate fuel loads, carbon content, timber volume

• Tell conifer from deciduous

• Identify damaged forest

Image at right shows a simple analysis, subtracting the bare earth surface model from a first return (highest hit) surface model to produce a canopy height model. Low canopy is violet, high is red. The shapes of individual trees are apparent, and the tallest tree in the forest can be easily found and measured.

Tallest tree at 252 ft!

Brush and grass

40-60 ft forest

50-80 ft forest

60-100 ft forest

100-125 ft forest

150-250 ft forest

135-190 ft forest

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Comparing the highest hit or surface and bare earth surface Comparing the highest hit or surface and bare earth surface provides provides

a detailed and accurate model of building area and heighta detailed and accurate model of building area and height

Building, 9,000 sq ft, 27 ft high

Building, 4,900 sq ft, 11 ft high

Residence, 2,300 sq ft, 12 ft high

Building, 19,850 sq ft, 89 ft high

Building, 16,750 sq ft, 79 ft high

Light standards, 54 ft high

Building, 20,100 sq ft, 155 ft high

Overpass, 23 ft high

Highway sign, 27 ft high

Powerline, 56 ft high

Parking structure, 79,400 sq ft, 3-20 ft high, sloped for drainage

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The highly detailed bare earth model allows for accurate location of The highly detailed bare earth model allows for accurate location of roads and provides easy access to unprecedented levels of detail about roads and provides easy access to unprecedented levels of detail about

slopes and shapesslopes and shapes Yellow lines are best current digital road map.

The lidar image can show where existing maps are inaccurate

or locate roads that are not on existing maps

or show where mapped roads do not exist

Because the bare earth model contains detailed information about the shape of the land surface, it is easy to construct a profile across a road to examine its construction and condition

Drainage ditch on uphill side

Roadcut not too steep

Properly crowned for drainage

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Stream channels are readily apparent on lidar bare Stream channels are readily apparent on lidar bare earth imagesearth images

GIS software can automatically find stream channels from lidar data

Blue lines are streams generated by ArcGIS

Comparing the lidar-derived streams with the current digital stream map shows that the current data are often wildly inaccurate

Dark blue lines are best current digital stream map, light blue are lidar-derived.

misses sinuous channel, climbs ridges

Crosses divide, mouth wildly off

cross divides

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In addition to accurately locating streams, lidar easily produces In addition to accurately locating streams, lidar easily produces accurate and detailed profiles and sectionsaccurate and detailed profiles and sections

Light blue line is lidar derived stream location, dark blue are section lines.

A detailed elevation profile down the stream shows areas of steep or gentle grade, waterfalls and pools. Culverts at road crossing show up as upward blips on the profile.

Stream section shows distinct floodplain and channel

Section shows “v” shape of rapidly downcutting stream

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What can you do with lidar?What can you do with lidar?You can quickly, cheaply, and accurately….You can quickly, cheaply, and accurately….• Find landslides, old cuts and gradesFind landslides, old cuts and grades• Measure and estimate fills and cutsMeasure and estimate fills and cuts• Find stream channels, measure gradientsFind stream channels, measure gradients• Measure the size and height of buildings, bridgesMeasure the size and height of buildings, bridges• Locate and measure every tree in the forestLocate and measure every tree in the forest• Characterize land coverCharacterize land cover• Model floods, fire behaviorModel floods, fire behavior• Locate power lines and powerpolesLocate power lines and powerpoles• Find archeological sitesFind archeological sites• Map wetlands and impervious surfacesMap wetlands and impervious surfaces• Define watersheds and viewshedsDefine watersheds and viewsheds• Model insolation and shadingModel insolation and shading• Map road center and sidelinesMap road center and sidelines• Find law enforcement targetsFind law enforcement targets• Map landforms and soilsMap landforms and soils• Assess property remotelyAssess property remotely• Inventory carbon Inventory carbon • Monitor quarries, find abandoned minesMonitor quarries, find abandoned mines• Enhance any research that requires a detailed and accurate 2D or Enhance any research that requires a detailed and accurate 2D or

3-D map3-D map

Page 17: Lidar and the Oregon Lidar Consortium

With the USGS funds to anchor the survey and ensure a large enough area for the lowest possible rate, Federal, State and local government agencies added on their areas of interest until the entire project had grown to over 2300 square miles and $1.1 M, with over 20 funding partners.

The Portland Lidar Consortium was the The Portland Lidar Consortium was the first large scale effort to collect lidar in first large scale effort to collect lidar in

Oregon.Oregon.

In 2003, the USGS funded DOGAMI for a pilot lidar survey to look for earthquake faults.

This was followed in 2005 by another USGS-DOGAMI flight in the Portland Hills, a USGS survey of the Columbia River Floodplain, and a survey by Oregon City of its urban growth boundary.

In 2006, the USGS provided DOGAMI with $100k to complete the City of Portland. DOGAMI formed the Portland Lidar Consortium to develop funding partnerships to increase the area.

“Hood to Coast” survey

Page 18: Lidar and the Oregon Lidar Consortium

The Oregon Lidar Consortium (OLC) originated in 2007 with a The Oregon Lidar Consortium (OLC) originated in 2007 with a request by DOGAMI to the 2007 legislature for funds to request by DOGAMI to the 2007 legislature for funds to

acquire acquire lidar over the inhabited parts of Western Oregon.lidar over the inhabited parts of Western Oregon.

• The legislature provided $1.5 M of the 4.5 M request and encouraged DOGAMI to seek funding partners to increase coverage

• The relatively small amount of funding requires prioritization to areas with significant local contributions

Blue hatch at left shows the original $4.5 M target based on the inhabited area of Western Oregon.

Red hatch shows the area that could be covered by $1.5 M, magenta shows existing data.

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DOGAMI Business Plan for the OLCDOGAMI Business Plan for the OLC

• Collection areas should be large and contiguousCollection areas should be large and contiguous• Collection areas initially anchored by significant contribution Collection areas initially anchored by significant contribution

from local funding partnerfrom local funding partner• OLC builds on anchor funding by finding additional partnersOLC builds on anchor funding by finding additional partners• State funds used to knit together partner areas State funds used to knit together partner areas • State funds are spent on the inhabited areas of the stateState funds are spent on the inhabited areas of the state• Collection areas completely outside the inhabited areas are Collection areas completely outside the inhabited areas are

fine if fully partner fundedfine if fully partner funded• Data in public domainData in public domain• Where possible, collection areas should include entire 6th field Where possible, collection areas should include entire 6th field

watershedswatersheds

Page 20: Lidar and the Oregon Lidar Consortium

DOGAMI selected a vendor to DOGAMI selected a vendor to provide lidar to the consortium.provide lidar to the consortium.

A nationwide RFP led to the selection for Watershed Sciences Inc. A nationwide RFP led to the selection for Watershed Sciences Inc. of Corvallis, Oregon, as the lidar vendor for the consortium under of Corvallis, Oregon, as the lidar vendor for the consortium under Oregon Price Agreement 8865.Oregon Price Agreement 8865.

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OLC lidar prices are a function of area. DOGAMI adds OLC lidar prices are a function of area. DOGAMI adds 10% to the vendor price for quality control and 10% to the vendor price for quality control and

management.management.

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Data SpecificationsData Specifications

• Laser spot size on ground 15-40 cm

1m

1m

• Aggregate pulse density > 8/m2

• 50% sidelap for complete double coverage

• Swath to swath consistency 15 cm (same point measured by adjacent swaths must have similar value)

• Absolute accuracy of each point

20 cm horizontal and vertical

Point cloud image of field and building: red points are from one swath, blue from another.

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DOGAMI provides three-way independent quality control for DOGAMI provides three-way independent quality control for

OLC data.OLC data. 1. Compare accurately surveyed

control points to the final lidar product to test absolute accuracy (+/- 20 cm).

GPS elevation = 50.40 m

Lidar elevation = 50.38 m

Error = 2 cm

OLC lidar image showing DOGAMI quality control points (red triangles) collected by RTK-GPS survey.

2. Compare adjacent points from overlapping swaths to test consistency (+/- 15 cm)

Colors indicate data from different swaths

Swath to swath differences, measured on hundreds of thousands of points per swath, average about 3 cm in this example

Lidar production software is used to automatically compare locations for huge numbers of points from overlapping swaths.

3. Inspect bare earth models for artifacts, processing errors

“Bird” anomalies produce spikes in bare earth model

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OLC Data ProductsOLC Data Products

Report and metadata !!Aircraft trajectories

3 ft pixel bare earth DEM ESRI format (quad tiles)

Ground points in LAS format (1/100 quad

tiles)

1 ft pixel intensity images (1/4 quad tiles)

Point cloud, LAS format 1/100 quad tiles

3 ft pixel first return DEM ESRI format (quad tiles)

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Data Distribution OptionsData Distribution Options

• NOAA LDART website (point cloud)NOAA LDART website (point cloud)• USGS CLICK website (point cloud)USGS CLICK website (point cloud)• USGS NED website (DEM)USGS NED website (DEM)• GEO spatial data library website (DEM)GEO spatial data library website (DEM)• METRO (Portland area only)METRO (Portland area only)• PSLC (“Hood to Coast” area only)PSLC (“Hood to Coast” area only)• DOGAMI website (planned)DOGAMI website (planned)• DOGAMI publications on disk or drive (planned)DOGAMI publications on disk or drive (planned)

Copies are provided on external hard drives as soon as DOGAMI completes QC.

Funding partners:

Public:

Page 26: Lidar and the Oregon Lidar Consortium

As of September 2008, 25 partners As of September 2008, 25 partners have added $2.7 million to the Oregon have added $2.7 million to the Oregon

Legislature’s $1.5 million.Legislature’s $1.5 million.

The City of Philomath

The City of Turner

Page 27: Lidar and the Oregon Lidar Consortium

As of September 2008, the OLC has been successful in As of September 2008, the OLC has been successful in building partnerships for several lidar collections around building partnerships for several lidar collections around

the state.the state.Current status at Current status at http://www.oregongeology.com/sub/projects/olc/default.htm

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Future PlansFuture Plans DOGAMI is seeking funds in future biennia to extend coverage to other parts of the state, as illustrated in the

conceptual draft below.


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