AAFC – Multiple Sites - Saskatchewan

LiDAR Survey Report

March, 2012

TABLE OF CONTENTS

1. SUMMARY……...……………………………………………………………………....1

2. MATRIX LiDAR SYSTEM……………………………………………………….........2

2.1 MATRIX Installation…………………...…………………………………............2

2.2 IMU-GPS Antenna Offset Survey………………………………………………...4

2.3 IMU-Laser Misalignment…………………………………………………………4

3. GPS SURVEY CONTROL…...………………………………………………………....5

3.1 GPS Control Points……………....……………………………………………….5

4. DATA COLLECTION…………………………………………………………………8

5. GROUND CHECKPOINTS……………………….…………………………………. 10

6. DATA PROCESSING……………………………..…………………………….……..13

6.1 LiDAR Point Clouds……………………………………………………….……13

6.1.1 LiDAR Tiles……………………………………………………………….13

6.1.2 Grounds Points……………………………………………………………..13

6.1.3 DTM Key Points…………………………………………………………...14

6.1.4 Vegetation………………………………………………………………….15

6.2 Grid Points……………………………………………………………………….15

6.3 Hillshades……………………………………………………………………...…16

6.4 Orthorectified Imagery…………………………………………………………..16

6.5 LiDAR Contours…………………………………………………………….…..17

APPENDIX A – GPS NETWORKS…………………………………………………..19

APPENDIX B – CONTROL PHOTOS…………………………………………….....23

1

1. SUMMARY

LiDAR Services International (LSI), a Calgary-based LiDAR company completed an airborne

LiDAR survey for Agriculture and Agri-Foods Canada (AAFC) in October-November 2011. The

Fall 2011 portion of the project involved collection of LiDAR data for the Pheasant Creek,

Roughbark, Moosomin, Braddock, Maple Creek, Eastend and Altawan project sites in Southern

Saskatchewan. LiDAR data was successfully collected, processed and delivered with the following

conditions:

LiDAR system installed in a Cessna 185 airplane owned and operated by CanWest

Corporate Air Charters of Slave Lake, Alberta

Airborne LiDAR collection occurred October 25-November 20th, 2011.

LiDAR data was collected at a flying height of 600 m above ground level and an air

speed of 240 km/h.

Riegl LMS-Q560 laser used pulsed at an approximate rate of 137 kHz resulting in a

computed average of ground spacing equal to 0.70 m

Horizontal Datum: NAD83 (CSRS)

Vertical Datum: CGVD28 orthometric heights (HTv2.0 height transformation model)

Map projection: UTM Zone 13 (Central meridian = 105 degrees west longitude)

Deliverable included:

o 1m bare earth and full feature grids in 1 km x 1 km tiles (ASCII XYZ format)

o 1m bare earth and full feature greyscale hillshades for each project area

(GeofTiff)

o Classified LiDAR point clouds and ASCII extractor program in 1km x1km

tiles (LAS v1.2 format)

o Orthorectified imagery with 0.2m pixel size in1 km x 1 km tiles (GeoTiff and

ECW format) and 1 MrSID image for each project area

o LiDAR contours 0.5m intervals (DWG and Shp format) in 1 km x 1 km tiles

o LiDAR tile Index (ESRI shp format)

o LiDAR survey report

2

2. MATRIX LIDAR SYSTEM

2.1 MATRIX Installation

The MATRIX LiDAR system was installed in a Cessna 185 (C-GAYZ) airplane, as shown below in

Figure 1, owned and operated by CanWest Corporate Air Charters of Slave Lake, Alberta.

Figure 1: Cessna 185 with MATRIX LiDAR system

The Riegl LMS-Q560 scanning laser and inertial measurement unit were mounted on a plate

extending out of the rear baggage hold, as seen in Figure 2. The system computers and data storage

devices were mounted to the floor in the rear of the aircraft, as seen in Figure 3. The GPS antenna

was mounted with a clamp on the front of the right wing next to the fuselage and the operator

controlled the MATRIX system with a monitor and keyboard from the front passenger seat.

Transport Canada has approved the installation of the MATRIX LiDAR system into this survey

aircraft.

Key sensors utilized in the MATRIX installation for the LiDAR survey included:

Riegl LMS-Q560 200 kHz laser scanner and data recorder

NovAtel V-3 dual frequency GPS receiver

NovAtel SPAN LCI 200 Hz Inertial Measurement Unit (IMU)

Canon EOS 1D Mark III, 10 Mega Pixel Digital Camera

3

Figure 2: Laser, Camera and IMU mounted on Cessna 185F

Figure 3: Matrix computers and data storage devices

4

2.2 IMU - GPS Antenna Offset Survey

Several parameters unique to each aircraft LiDAR installation must be determined in order to

produce accurately positioned LiDAR point clouds. These parameters include the three dimensional

vector (lever-arm) between the GPS antenna phase center and the inertial body reference. Using a

total station and prisms at several points surrounding the aircraft, redundant distances and angles to

the IMU unit and GPS antenna were observed. The observations were then subjected to a least-

squares adjustment to compute the final lever arm values. As this particular aircraft had been used

by LSI for LiDAR surveys many times in the past, the GPS to IMU distance had been previously

calculated. A portion of a GPS-IMU offset survey on the aircraft is shown in Figure 4 below.

Figure 4: Cessna 185F lever-arm survey

2.3 IMU – Laser Misalignment

LiDAR calibration passes were made at the beginning and end of each flight to allow for the

determination and verification of the roll, pitch and heading misalignment angles between the IMU

measurement axis and the laser sensor. The calibration passes consisted of three to four flight lines

flown at orthogonal and parallel headings at the project flying height and speed. Features such as

buildings and roads were used to compute and verify the misalignment angles for the project install.

5

3. GPS SURVEY CONTROL

3.1 GPS Control Points

High-precision kinematic GPS solutions were obtained for the LIDAR data collection missions

using differential GPS (DGPS) survey techniques. DGPS requires a static GPS receiver

collecting data at a known ground control point in the vicinity (generally within 35 km) of the

airborne (remote) GPS receiver during LiDAR data collection. All of the collected and

processed LiDAR and imagery data is referenced to the 3D coordinates of the ground control

points.

For consistency and accuracy high order, Federal Geodetic Survey Division (GSD) GPS control

points were used for referencing of all the project sites. LSI surveyors monumented and

increased the density of the existing GSD control networks to allow GPS benchmarks to be

within 35km of the project areas and at local utilized airports. To determine the accurate

positions of the new GPS benchmarks four GPS survey networks were created; Pheasant Creek,

Moosomin, Roughbark and one for the areas surrounding Swift Current including Braddock,

Eastend, Maple Creek and Altawan. Figures of the four control point networks can be seen in

Appendix A.

Below, in Tables 1 and 2 are the control coordinates used for the 2011 AAFC LiDAR survey. Table

1 are the geodetic control coordinates in NAD83 (CSRS) with ellipsoid heights and Table 2 contains

the UTM Zone 13 positions with CGVD28 orthometric heights utilizing the HTv2.0 height

transformation model. Additionally photos of all of the GPS control points can be seen in Appendix

B.

6

Table 1: GPS Control Coordinates NAD83 (CSRS)

ID Monument

Type Latitude Longitude Ellipsoidal Height (m)

HT2.0 Geoid (m)

Moosomin 68s273 GSD 50 12 57.94860 -101 48 47.10640 560.030 21.677

MoosominGPS LSI spike 50 02 55.71764 -101 40 36.17673 520.544 21.543

VirdenAIR LSI spike 49 52 35.96509 -100 55 08.02237 419.151 22.456 Pheasant

Creek

84s275 GSD 50 50 46.3946 -103 49 53.5362 570.040 20.481

PCGPS LSI spike 50 44 13.32691 -103 20 00.71256 561.434 20.741

ReginaAIR LSI spike 50 25 55.85721 -104 39 11.67804 555.748 19.597

Roughbark 94v053 GSD 49 40 43.339 -102 58 38.20920 604.480 19.035

WeyburnAIR LSI spike 49 41 49.63949 -103 48 26.58886 566.354 18.872

WeyGPS LSI spike 49 31 22.10015 -103 44 52.62617 555.544 18.654

SW Sask 80s094 GSD 49 43 37.17512 -108 09 29.59387 854.737 16.531

94v050 GSD 49 59 23.10819 -109 28 05.92757 771.362 17.233

94v051 GSD 50 14 57.87090 -107 46 09.26740 798.870 17.893

A230581 GSD 49 58 39.18304 -110 45 46.26312 706.423 17.143

Admiral LSI spike 49 43 39.86000 -107 54 07.00811 777.775 16.810

Altawan LSI spike 49 13 26.49991 -109 49 03.84398 918.015 15.603

Braddock LSI spike 50 06 22.46381 -107 18 06.31430 744.920 18.142

Cadillac LSI spike 49 46 07.88578 -107 35 08.94909 740.030 17.243

Eastend LSI spike 49 30 34.13721 -108 45 48.76528 896.127 16.016

MapleAIR LSI spike 49 53 49.20037 -109 28 50.21885 750.623 16.926

Medicine Hat LSI spike 50 01 22.50574 -110 43 27.34653 699.783 17.254

Russell LSI spike 49 54 13.19900 -107 30 22.64803 756.087 17.545

Shaunovan LSI spike 49 39 18.09667 -108 24 25.94074 904.853 16.261

USBorder LSI spike 49 00 01.64843 -109 43 57.33403 826.921 15.388

7

Table 2: GPS Control Coordinates UTM Zone 13

ID Easting (m) Northing (m) CGVD28

Elevation (m)

Moosomin 68s273 727350.326 5567518.961 581.706

MoosominGPS 737905.533 5549349.536 542.087

VirdenAIR 793186.537 5532907.521 441.607 Pheasant

Creek

84s275 582260.100 5633374.760 590.520

PCGPS 617591.903 5621907.092 561.434

ReginaAIR 524627.481 5586741.982 575.344

Roughbark

94v053 645921.284 5504872.873 623.515

WeyburnAIR 586005.920 5505638.923 585.226

WeyGPS 590614.525 5486329.411 574.197

SW Sask

80s094 272399.306 5513065.499 871.268

94v050 179757.204 5547064.648 788.594

94v051 302579.154 5570031.036 816.762

A230581 86921.816 5552067.817 723.565

Admiral 290868.468 5512402.603 794.584

Altawan 149262.559 5463539.272 933.618

Braddock 335411.637 5552980.174 763.062

Cadillac 313805.352 5516140.380 757.272

Eastend 227574.018 5490904.144 912.142

MapleAIR 178257.547 5536810.399 767.550

MedicineHat 90073.167 5556894.640 717.036

Russell 320032.520 5530931.881 773.632

Shaunovan 254096.096 5505851.789 921.112

USBorder 153904.113 5438305.786 842.309

For future surveys in the project areas it is important that at least one of the control points listed in

the above tables are used for geo-referencing in order to obtain positions in agreement with the

LiDAR data collected in 2011.

8

4. DATA COLLECTION

The LiDAR survey was completed over 13 flights between October 25th and November 20

th, 2011.

As the project extended late into the fall there were some delays in collection due to snow and as a

result only the areas of Pheasant Creek, Roughbark, Moosomin, Braddock, Maple Creek, Eastend

and Altawan were collected and Admiral, Russell Creek, Cadillac-Gouveneur and Lafleche areas

were not. In total there were7 stand by days with no flight missions due to snow or high winds.

Below in Table 3 is a complete listing of the days each project area was collected.

Table 3: AAFC Fall 2011Flight Summary

Project Area Date Julian Day

Flight Time (GMT) GPS

Pheasant Creek Oct-25 JD298 19:17-21:50 Regina Air, PheasantCreekGPS

Roughbark Oct-27 JD300 16:29-19:14 WeyburnAIR, WeyGPS

Moosomin Oct-28 JD301 19:45-22:41 68s273, MoosominGPS

Moosomin Oct-29 JD302 15:02-18:21 MoosominGPS, VirdenAIR

Braddock Oct-30 JD303 21:04-23:14 94v051, Braddock

Braddock Oct-31 JD304 21:23-23:54 94v051, Braddock

Braddock Nov-01 JD305 19:28-23:13 94v051, Braddock, Russell

Maple Creek Nov-08 JD312 16:59-20:38 94v051, 94v050, MapleAIR

Maple Creek Nov-08 JD312 21:12-23:31 94v051, 94v050, MapleAIR

Eastend Nov-09 JD313 16:15-19:54 Eastend, Shaunovan, MapleAIR

Maple Creek Nov-16 JD320 15:15-19:07 Medicine Hat, A230581, MapleAIR

Maple Creek/ Eastend Nov-16 JD320 20:39-23:31 MapleAIR, Eastend

Altawan Nov-19 JD323 17:42-19:56 MapleAIR, Altawan, US border

Altawan Nov-20 JD324 16:53-21:10 MapleAIR, Altawan

Several airports were used to base collection missions out of, depending on proximity to the project

area. Airports utilized included; Regina International Airport, Weyburn Airport, Virden Airport,

Swift Current Regional Airport, Maple Creek Airport and Medicine Hat Municipal Airport.

9

All flight lines were planned and flown at 600 m above ground level and an approximate speed of

240 km/h. The parallel flight lines were collected with 400 m separation resulting in approximately

40% side overlap of the LiDAR and imagery data. In addition, for each area one or more

perpendicular cross or tie lines were flown for quality control. Below in Figure 5 is an illustration of

the planned and collected flight lines for the Maple Creek project area.

Figure 5: Maple Creek flight lines collected

During data collection the Q560 laser pulsed at 137 kHz with full waveform multi-return capability

resulting in an average point spacing of 0.70 m, or 2.0 points per square metre. The airborne GPS

receiver logged at 1-second intervals simultaneously with the IMU recording the orientation and

accelerations of the sensor plate every 0.005 seconds. Also, downward photos were collected with

the Canon EOS-1D Mark III digital camera every 2.2 seconds for an average of 60% forward

overlap between consecutive photos.

10

5. GROUND CHECK POINTS

To ensure data accuracy and quality assurance of the LiDAR data, multiple ground check point data

verification tests were performed. Independent, high accuracy GPS ground check points were

collected on foot with a pole mounted GPS receiver and antenna as recommended in the ASPRS

Guidelines – Vertical Accuracy Reporting for LiDAR Data V1.0.

Two check point surveys were conducted, one at the Swift Current and one at the Maple Creek

airports, where the majority of flights were based out of. The check points overlaid with the grey-

scale intensity images at the Maple Creek and Swift Current Airports are shown below in Figures 6

and 7. Several calibration passes were performed at the start and end of each flight at these airports.

Ground points were classified from each individual calibration pass, and the resulting triangulated

surface model was compared to the independently-observed ground check points. The resulting

height residuals and statistics for each calibration pass are shown below in Tables 4 and 5.

Figure 6: Check points at Swift Current Airport

11

Figure 6: Check points at Maple Creek Airport

Table 4: Check Point Residuals for Swift Current Airport Checkpoints

Flight Line Average Dz (m) Standard Dev

(m)

RMSE (m)

Accuracy @ 95%

Confidence Interval

(m)

JD305flt1_172 -0.023 0.021 0.031 0.061

JD305flt1_173 -0.027 0.019 0.034 0.065

JD305flt1_174 -0.022 0.021 0.030 0.059

JD305flt1_175 -0.044 0.021 0.049 0.096

JD305flt1_198 0.014 0.023 0.027 0.053

JD305flt1_199 -0.059 0.025 0.065 0.127

JD305flt1_200 -0.007 0.021 0.022 0.042

JD305flt1_201 -0.056 0.021 0.059 0.117

Average -0.0283 0.0213 0.039 0.078

12

Table 5: Check Point Residuals for Maple Creek Airport

Flight Line Average Dz

(m)

Standard Dev (m) RMSE (m)

Accuracy @ 95%

Confidence Interval

(m)

JD312flt1_301 -0.042 0.020 0.046 0.091

JD312flt1_302 0.022 0.032 0.039 0.076

JD312flt1_304 -0.059 0.025 0.064 0.125

JD312flt1_336 0.023 0.015 0.028 0.054

JD312flt1_337 -0.039 0.032 0.051 0.099

JD320flt1_428 0.002 0.017 0.017 0.033

JD320flt1_429 -0.041 0.015 0.043 0.085

JD320flt1_430 0.016 0.014 0.021 0.042

JD320flt1_431 0.029 0.013 0.033 0.064

JD320flt2_432 0.033 0.016 0.036 0.071

JD320flt2_433 -0.006 0.012 0.014 0.026

JD320flt2_434 0.024 0.012 0.027 0.053

JD320flt2_449 -0.003 0.016 0.016 0.031

JD320flt2_450 0.020 0.013 0.024 0.048

JD320flt2_451 -0.009 0.013 0.016 0.031

JD320flt2_452 0.017 0.015 0.023 0.045

JD323flt1_453 0.008 0.017 0.019 0.037

JD323flt1_454 -0.038 0.018 0.042 0.081

JD323flt1_455 -0.098 0.017 0.099 0.194

JD323flt1_456 -0.043 0.019 0.047 0.093

JD323flt1_464 -0.013 0.161 0.021 0.040

JD323flt1_465 0.018 0.017 0.025 0.048

JD323flt1_466 0.036 0.019 0.041 0.079

JD323flt1_467 -0.004 0.015 0.016 0.031

JD324flt1_468 -0.011 0.018 0.021 0.042

JD324flt1_469 0.007 0.019 0.019 0.039

JD324flt1_470 0.084 0.016 0.086 0.168

JD324flt1_471 -0.007 0.021 0.022 0.043

JD324flt1_492 0.009 0.018 0.020 0.039

JD324flt1_493 -0.015 0.019 0.025 0.048

JD324flt1_494 -0.026 0.016 0.030 0.059

JD324flt1_495 0.009 0.021 0.022 0.044

Average -0.003 0.022 0.032 0.064

13

6. DATA PROCESSING AND DELIVERABLES

6.1 LiDAR Point Clouds

6.1.1 LiDAR Tiles

Unclassified point clouds were generated for each individual flight line from the raw laser data, the

GPS-IMU post-processed solutions and the measured system calibration parameters. The point

clouds were then imported into 1 km x 1 km tiles using TerraSolid software so that the average

quantity of points per tile was around 4 million. The name for each tile was derived from the

coordinate of the southwest corner of the tile. The tile naming structure is as follows:

Southwest corner coordinate of tile = (East, North) = (484000, 5269000)

Tile name = EEENNNN = 4845269

A total of 1226 LiDAR tiles were created to cover the seven project areas. A 50 m buffer was added

to the project boundaries and any excess points outside of the buffer were clipped from the project.

The LiDAR tiles were delivered in LAS 1.2 format along with an ASCII extractor program.

6.1.2 Ground Points

An initial automatic ground classification was applied to the tiles. The automatic ground macro

classified ground points using a sequence of steps that identifies the lowest LiDAR point in an area

and then finds neighbouring ground points based on user-specified iteration angles and tolerances.

After the automatic ground classification, trained technicians inspected each tile and either added or

removed points from the Ground class that were incorrectly classified by the automatic ground

macro. This was done using the TerraSolid suite of LiDAR editing tools in the MicroStation

environment, as displayed in Figure 8 below.

14

Figure 8: LiDAR ground editing using TerraSolid software

6.1.3 DTM Key Points

After completion of the manual ground editing, DTM Key Points were classified from the Ground

point class. The automatic DTM Key Point classification selects key points from the Ground class

and chooses neighbouring Ground points using a horizontal tolerance of 10 m and a vertical

tolerance of 10 cm. That is, the maximum horizontal distance between DTM Key Points is 10 m and

the maximum vertical distance is 10 cm.

The DTM Key Points are a subset of the Ground points taken directly from the Ground class. The

DTM Key Point class typically has 40-80% less points than the original Ground class, depending on

the terrain. Because the DTM Key Points are taken from the Ground class, it is important that the

Ground class never be used by itself. Either the DTM Key Point class can be used alone, or the

DTM Key Point and Ground classes can be used together. The DTM Key Point and Ground

classes together will produce the maximum possible terrain detail, with the largest number of points.

15

6.1.4 Vegetation

The points remaining after the ground classification were classified into the Low Vegetation class (0

to 0.25m above ground), and the High Vegetation class (greater than 0.25 m above ground). The

vegetation classes include all objects and structures above the ground, including buildings,

transmission lines, bridges, fences, vehicles and piles of non-earth materials (garbage, wood, etc.).

Because of the large quantity of High Vegetation points, an automatic thinning classification was

performed to reduce the number of points in the High Vegetation class while maintaining the outline

of the forest canopy. The quantity of High Vegetation points was reduced by up to 50% and the

points removed from the High Vegetation class were saved in the Thinned Vegetation class.

6.2 Grid Points

Bare earth grid points were created at a 1 m interval and delivered in ASCII XYZ format using the

same tile structure as the LiDAR tiles. The bare earth grid point elevations were derived from a TIN

surface model of the combined DTM Key Point and Ground classes in the LiDAR point cloud tiles.

It should be noted that the grid point elevations have been interpolated from the LiDAR points and

may contain greater uncertainty depending on the amount of interpolation performed.

Full feature grid points were also created at a 1 m interval and delivered in ASCII XYZ format. The

full feature grid point elevations were derived from the highest point in the High Vegetation class.

At coordinates with no High Vegetation points the elevation of the corresponding bare earth grid

point was applied.

16

6.3 Hillshades

Georeferenced grayscale raster images with a 1 m pixel size were delivered in GeoTIF format. The

bare earth hillshade images were derived from the bare earth grid points and the full feature hillshade

images were derived from the full feature grid points. The hillshades were created using a 315

degree sun azimuth and 45 degree sun angle. A total of 1 bare earth and 1 full feature hillshade in

GeoTiF format were created for each project area. An example of a portion of a bare earth hillshade

is shown below in Figure 9.

Figure 9: Bare earth hillshade

6.4 Orthorectified Imagery

Georeferenced color digital orthophoto mosaics with 20 cm pixel size were delivered in GeoTIF and

ECW formats. The TIF and ECW mosaics were delivered in the same1 km x 1 km tiles as the

LiDAR data, and complete mosaics for each area in MrSID format were also provided.

17

The digital photos were orthorectified using the ground model created from the DTM Key Points.

With orthorectification, only features on the surface of the ground are correctly positioned in the

orthophotos. Objects above the surface of the ground, such as building rooftops and trees, may

contain horizontal displacement due to image parallax experienced when the photos were captured.

This is sometimes apparent along the cut lines between photos. For positioning of above-ground

structures it is recommended to use the LiDAR point clouds for accurate horizontal placement.

6.5 LiDAR Contours

LiDAR contours with an interval of 0.5m were delivered in DWG and ESRI Shape format and the

files were provided in the 1km x 1km tile structure.

The contours were derived using the contour keypoints modeling function in the TerraSolid software

package. Contour keypoints were modeled from the ground class at a maximum vertical distance of

0.5m and a horizontal distance of 20 m. Breaklines were not used around water features therefore a

uniform height of water bodies is not necessarily present if overlapping data was collected on

different days. Major contours were defined every 5m and minor contours every 0.5 m. An

illustration of the contours is shown below in Figure 10.

Figure 10: LiDAR Contours

18

LSI greatly appreciates the opportunity to have performed the LiDAR survey for Agriculture and

Agri-Foods Canada and is available for any questions or comments regarding the survey or the

contents of this report.

LiDAR Services International Inc. Phone: (403) 517-3130

400, 3115 – 12 St. N.E. Fax: (403) 291-5390

Calgary, Alberta T2E 7J2 Website: www.lidarservices.ca

19

APPENDIX A

GPS Networks

Moosomin GPS Network

20

Pheasant Creek GPS Network

21

Roughbark GPS Network

22

South West Saskatchewan GPS Network

23

APPENDIX B

Control Point Photos

68s273

MoosominGPS

24

VirdenAIR

84s275

25

Pheasant Creek GPS

Regina AIR

26

94v053

Weyburn AIR

27

Weyburn GPS

80s094

28

94v050

94v051

29

A230581

Admiral GPS

30

Altawan GPS

Braddock GPS

31

Cadillac GPS

Eastend GPS

32

MapleAIR GPS

MedicineHat GPS

33

Russell GPS

Shaunovan GPS