Application of dual output LiDAR scanning system for power transmission line data capture

Application of dual output LiDAR scanning system for power transmission line data capture

European LiDAR Mapping ForumSalzburg Congress Austria 29-30 November 2011

Pedro Llorens(1) – Ron Roth (2) – F. Javier Luque (1) – Alfonso Gómez (1) – Francisco J. Arjonilla (1)

(1) Stereocarto, S.L. – Madrid, Spain, (2) Leica [email protected]

mailto:[email protected]

2European LiDAR Mapping Forum

Salzburg Congress Austria 29-30 Nov 2011Application of dual output LiDAR scanning system for power transmission line data capture

Group of companies specialized in geoinformation: Capture, process and exploitation

Core companies:

• Stereocarto: General geoinformation process and exploitation (orthophoto, GIS,...)

• HIFSA: Aerial survey flights• Cartogesa: Feature extraction and edition• Terra XXI: Consultancy

Working since 1964

Belongs to the engineering firm Inypsa (public company in Madrid stock exchange)

R & D & Innovation division

International activity:

• 80% turnover outside Spain• Subsidiaries in Portugal, Italy, Romania, Ecuador, Brazil and more.

Stereocarto Group



One of Stereocarto strengths is massive data capture:

5 Digital cameras:

• 3 Z/I DMC• 1 Leica ADS40• 1 Leica RCD105

3 LiDAR systems

• 2 Leica ALS50 II• 1 Leica ALS60

5 airplanes

• 3 owned (Beechcraft B200, Cessna 402, 404)• 2 leased (Cessna 421, Piper Aztec)

Flight performance in 2009

• 300,000 sq. Km. digital aerial imagery• 100,000 sq. Km. LiDAR survey

Current biggest project

• Ecuador (2/3 country – 240,000 sq. Km.): Aerial imagery, LiDAR and 50cm orthophoto

Main resources and projects



Powerline analysis to detect potential clearance violations (points failing to keep security distances).

Powerline design, planning, maintenance, modification and rerating

Powerline geometry studies objectives



LiDAR is an excellent tool to model powerlines thanks to its unique features

Multiple returns capability

Uniform accuracy

High level of detail

High efficiency and productivity (e.g. bigger swath)

LiDAR applied to powerlines



Overhead cable modelling

• Catenary parameters

Electricity pylons

Terrain in the Right-of-Way (ROW) corridor

Vegetation close to the powerline (inside and outside of the ROW).

Infrastructure and objects in the powerline surroundings.

Information extracted from LiDAR data



New lines planning

Existing lines inventory:

• 3D modelling of high voltage powerlines with catenary extraction

Lines rerating or repowering

• Thermal capacity analysis of transmission lines

Environmental:

• Critical distances analysis to vegetation (forest fire prevention)

Obstacle analysis in the powerline ROW

Studies include capture at ambient conditions (wind and temperature) and simulations of extreme weather cases

Powerline applications of LiDAR



REE is the Spanish TSO (Transmission System Operator)

REE is the unique responsible of electricity transportation or transmission in Spain (Iberian Peninsule and islands)

REE manages nearly 40.000 Km of transmission powerlines, mainly 400 KV and 220 KV

Recently REE is using LiDAR technology to capture powerlines in maintenance, rerating and ROW vegetation management projects

Red Eléctrica de España (REE)



REE transmission grid



“Data acquisition with laser scanning technology (LiDAR) for determination of points with critical distances between high voltage cables belonging to the REE grid and trees or surrounding vegetation”

Area covered: 837 linear kilometers

• 429 Km 400KV• 408 Km 220KV

The project was part of REE vegetation management program

It should identify areas where field brigades should remove danger trees and branches

Project objective



Powerlines covered



Required data:

• Listing of critical distance points. • Phase conductor with critical distance.• Cross section to scale of every point with critical distance.• Scale maps of each span containing points with critical distances to

vegetation• Optionally point clouds

All data supplied in three different cases (one captured and two calculated):

1. Under existing temperature (measured) and wind conditions at the time of flight (Captured geometry)

2. Zero wind and max wire load (usually 50ºC temperature) (Calculated geometry)

3. 120 km/h wind across track and 15ºC. (Calculated geometry)

Deliverables



Project done in summer

Flight planning and execution 2 weeks

Trajectory calculation 1 week

Point cloud and basic LiDAR post processing 2 weeks

Cable extraction, simulations and deliverables preparation 6 weeks

Schedule



Initially planned with our ALS50 II

Finally used a new ALS70 HP

Spacing parameters required the use of helicopter instead of fixed wing aircraft

Technical resources

Technical resources Model Manufacturer

Helicopter Eurocopter Ecureuil AS350 B3 Eurocopter

Laser scanner ALS 70-HP (Orig. ALS50II) Leica

IMU IPAS 20 Leica

Ground reference stations System 1200 Leica



ALS70-HP

LS70-LP Laser Scanner

SC70 System Controller

LC60 Laser Controller

OC50 Pilot Display

GI40 Guidance Indicator

OC52 Operator Display

MM70 Mass Memory



LiDAR sensor mounted on Dart POD .

Sensor mounting

ALS with / without RCD, Dart pod

In pod

In cabin



Main parameters:

• Field of vision (FOV)• Pulse rate• Scan rate

Constraints:

• Point density• Point spacing• Fooprint diameter

Other requirements:

• Detectable object size• Flying height• Aircraft speed• Swath width / Line spacing• Relieve

Sensor parameters



Sensor parameters



Cable detection

• Across track spacing equal to pulse footprint size is used – 12cm for 500 m flying height

Line surrounding objects detection

• Despite a 2-3m along track spacing would be enough to capture the cable and determine catenary parameters, ALS70-HP reached <30cm allowing detailed capture of vegetation and any object in the ROW and surroundings

Sensor parameters for cable capture

Across trackspacing 0,12cm

Pulse footprint size 0,12cm

Along track spacing 0,27 to 0,90cm

Cable

Flight direction



Flight parameters

Flying heigtht AGL 500 meters

Ground speed 40 (72)Knots(Km/h)

ParameterALS50I

IALS70-

HP Units

Pulse rate150.00

0 500.000 Hertz

FOV 28.5 28.5 deg

Average point density > 28 > 95

pts/m2

Full swath width > 250 > 250meters

Max point spacing across track 0,13 0,12

meters

Max point spacing along track 0,90 0,27

meters

Flight parameters

LiDAR



Planned parameters result in:

• Relative accuracy:• X, Y ~ 6 cm• Z ~ 7 cm• Required 0.50 m

• Absolute accuracy:• X, Y ~ 25 cm• Z ~ 20 cm• Required 1 m

Accuracy



LiDAR flight planning and

execution

Process

Classification

Cable extraction

Catenary definition

LiDAR & simulateddata integration

Critical points determination

Deliverable generation

RAW Data

Point cloud

Classified point cloud

Cable parameters

Point cloud with critical

points

Plans & cross sections

Weather case generation

New cable vectors

Workflow



Point cloud

LiDAR data process



Classification

Vegetation & buildingsTerrain

PylonOverhead line

LiDAR data process



Cable extraction

• Determination of points belonging to the cable in the point cloud

LiDAR data process



Critical points identification

• Identification of potencial clearance violations under existing conditions at the time of flight

Captured data



Deliverable

Captured data



Deliverable

Captured data



Cross section

Captured data



Catenary parameters and cable position determination under alternative scenarios or weather cases.

• Maximum load condition• Conductor temperature increases and suffers dilatation so it gets closer to the

ground. Case temperature defined by the customer, usually 50º.

• Extreme across track wind situation.• At 15ºC, a 120 Km/h across track wind is considered, resulting in a deviation of the

cable from the vertical plane. In nearly 1Km spans this means several meters.

Simulation done with PLSCADD and propietary software from Inypsa

Data had to be captured in a wide area around the powerline in order to take into account the new position of the overhead cable in the weather cases

The existing temperature conditions at the time of flight had to be registered to calculate the derived weather cases

• This was done lowering the helicopter next to the powerline every 10-15 Km• Temperature was registered with a helicopter probe

Weather case simulation



Overhead line modelingengine

LiDAR dataConductors properties database

Insulators database

catenary @ max T / max

E. load

catenary @ max cross-

wind pressure

load

Ambient Temp

Power line info

Inypsa simulation application



Point cloud

Simulated cable

Simulated data



Point cloud cross section

Cable simulationWind case

Cables

Cable simulationMax load

Simulated data



Deliverable

Extreme wind case

Simulated cable



Deliverable

Extreme wind case



Cross section

Extreme wind case



Critical points:

• Data grouped by spans between pylons.• Cable parameter listings (captured and simulated).• Coordinate listings of critical points.

LiDAR data:

• Point clouds (optional)

Alphanumeric deliverables



Critical distances

Pylon Distance to pylon Cable clearance Object class East North Elevation

1 16,1 4,99 vegetation 333871,86 4215925,71 669,77

2 22,29 0,12 vegetation 334137,93 4216678,86 720,61

2 22,3 0,18 vegetation 334137,98 4216678,85 720,66

2 22,3 0,22 vegetation 334138,05 4216678,83 720,63

3 22,3 3,79 vegetation 334137,98 4216678,85 720,66

3 22,3 3,82 vegetation 334138,05 4216678,83 720,63

3 22,3 3,83 vegetation 334137,93 4216678,86 720,61

2 9,99 3,16 vegetation 334169,98 4216834,57 692,72

2 9,99 3,21 vegetation 334170,06 4216834,55 692,68

2 9,99 3,24 vegetation 334170,13 4216834,53 692,67

2 9,98 3,58 vegetation 334170,39 4216834,45 692,38

2 9,98 3,59 vegetation 334170,32 4216834,47 692,36

2 9,97 3,6 vegetation 334170,46 4216834,43 692,38

2 9,99 3,8 vegetation 334170,00 4216834,54 692,09

2 9,97 3,84 vegetation 334170,57 4216834,4 692,17



Buildings clearance



Terrain clearance



Growing vegetation

Vegetation clearance



Falling trees danger

Vegetation clearance



High level of detail – pylon 1









Maximum load cable modelling in Google Earth

Weather case visualization



Extreme across track wind (120 Km/h) cable modelling in Google Earth

Weather case visualization



ALS70-HP allows doubling flight speed over 80 knots without compromising spacing

Finally speed is only limited by helicopter maneuverability

• Speed at bends• Terrain following with hight slopes

Point density and accuracy do not limit flight specification

Some consistency issues with input data

• Pylon numbering• Pylon position

LiDAR data editing software considers catenaries contained in a vertical plane so it is not able to model the 120Km/h wind case as the catenary gets out of that plane. This forced the development of an specific sowtware tool to determine distance from cables in any position to obstacles, trees and ground.

Conclusions


Salzburg Congress Austria 29-30 Nov 2011STEREOCARTO, S.L.

OFICINA CENTRAL:PASEO DE LA HABANA Nº 200, 28036 MADRID, ESPAÑA. TELF. +34 913431940FAX: +34 913431941

HTTP://WWW.STEREOCARTO.COM

OFICINAS:

EspañaPortugalItaliaRumaniaBrasilColombiaEcuador

STEREOCARTO, S.L.

OFICINA CENTRAL:General Díaz Porlier, 49 28001 Madrid, España. Telf. +34 911211800Fax: +34 914021609

http://www.stereocarto.com

Technology

Application of dual output LiDAR scanning system for power transmission line data capture