GPS area measurements

Transcription

1 Kick-off 2010, Ispra, April / 24 GPS area measurements Krasimira Ganisheva, Cozmin Lucau GeoCAP, JRC Ispra

2 Kick-off 2010, Ispra, April / 24 Outlines GPS devices certified by Navcert or validated by MS Example of GPS validation tests in some MS Direction effect and tree canopy Differential correction: DGPS code versus VRS carrier phase

3 Kick-off 2010, Ispra, April / 24 GPS devices certified by Navcert 1 new device certified since Nov 2009: Device Topcon GRS-1 with Ascos PED real time correction service Measurement method vertex Category (buffer) A (0,10m) -> certificate expired -> legal issue (certificate valid if no technical change) -> no renewal from manufacturer -> Manufacturers (Leica, Trimble) ready to certify their own equipment under JRC supervision

4 Kick-off 2010, Ispra, April / 24 GPS devices validated by MS (with JRC support/review) November 2009: 8 models validated MS Device Method Buffer (m) GR Garmin 60 continuous 1,25 (except if trees) BG Magellan MobileMapper CX + voice application vertex/continuous 0,75 CZ Topcon Legacy H DGPS continuous 0,75 DE Topcon GMS 2 + Beacon vertex 0.75 SI Trimble GeoXT with EGNOS vertex/continuous 0,75 UK Trimble Pro XRS (Beacon and OmniStar corrections) vertex <0,50 JRC (PL) Trimble GeoXT and GeoXH continuous 0,75 More info on webpage

5 Kick-off 2010, Ispra, April / 24 April 2010: 13 models validated by MS Device, type MS Measurement method Buffer width, m Asus PDA + Haicom GPS antenna DK continuous 0,75 Garmin 60 GR continuous 1,25 Leica GS50 with Beacon correction DK vertex 0,50 Leica SR530 with Leica Smart Net correction DK vertex 0,50 Magellan MobileMapper CX (with voice application) BG vertex/continuous 0,75 Magellan MobileMapper CX - standalone BG vertex/continuous 1,00 Magellan MobileMapper CE - standalone BG vertex/continuous 1,00 Topcon DGPS reciever Legacy H CZ continuous 0,75 TOPCON GMS-2 with Beacon correction services DE (Rheinlandpfalz) vertex 0,75 Trimble GeoXT - standalone JRC (PL) continuous (1s) 0,75 Trimble GeoXH - standalone JRC (PL) continuous (1s) 0,75 Trimble GeoXT with EGNOS correction SI vertex/continuous 0,75 Trimble Pro XRS with Beacon corrections EN vertex 0,50 Trimble Pro XRS with Omnistar corrections EN vertex 0,50

6 Kick-off 2010, Ispra, April / 24 GPS validation: summary Validation tests planned for > Common questions from MS (CZ, FR, CY, LV) on test protocol Number & type of parcels (size, shape, border)? Number of repetitions, sets, operators? -> 2 examples (JRC and SI)

7 Kick-off 2010, Ispra, April / 24 Example 1 of experimental design: JRC test (PL, 2009) Devices/Software tested: Trimble GeoXT (internal antenna) with Terrasync version 2.53 Professional edition Trimble GeoXH (internal antenna) with Terrasync version 3.30 Professional edition Measurement protocol: No of parcels Operators Sets Repetitions Days 6 (3 with trees on boundary) 2 10 (5days x 2op) 4 5 Device settings: Measurement mode continuous (1s) EGNOS switched off Elevation mask 10 SNR 20 DOP Max PDOP:10

8 Kick-off 2010, Ispra, April / 24 Examples of fields used for validation tests in PL Area: 0.3 to 1.5 ha, Perimeter: 220 to 650m Parcel A Area = 1,0ha, P=506m Parcel B Area = 1,5ha, P=508m Parcel C Area = 0,4ha, P=245m Parcel D Area = 0,3ha, P=221m Parcel E Area = 0,8ha, P=659m Parcel F Area = 1,1ha, P=419m ~ cm The testing fields included different parcel size, shape and border obstruction

9 Kick-off 2010, Ispra, April / 24 Direction effect case of test with Trimble Geo XT standalone Parcel D: S=0,3ha, P=221m, 20 measurements (10 CW and 10 ACW), continuous mode error_on_perimeter anticlockw ise The parcel area when measuring in clockwise direction is constantly larger than the parcel area in anticlockwise Result: Difference, expressed as an error on perimeter of 62cm (mean acw = -37cm, mean cw = 25cm) between measurements taken cw and acw Possible reason: operators do not hold the antenna of the receiver on the field border -> can be eliminated by taking special care to the measurement protocol direction clockw ise Each Pair Student's t 0.05

10 Kick-off 2010, Ispra, April / 24 Tree canopy influence on buffer width R expressed as a buffer on perimeter [m] 1,2 1 0,8 0,6 0,4 0,2 0 border partially obstructed by trees, rectangular shape trees border partially obstructed by trees, irregular shape border partially obstructed by trees, rectangular shape open horizon, rectangular shape open horizon, elongated shape open horizon, square shape A B C D E F Parcel type: 3 with obstructions Open horizon GEO XT GEO XH 3 with open horizon

11 Kick-off 2010, Ispra, April / 24 Example 2 of experimental design: SI test (2009) Devices/Software tested: Trimble GEO XT with EGNOS correction (Hurricane external antenna) with ArcPAD version 7.0 Measurement protocol: No of parcels Operators Sets Repetitions Days 7 (3 with obstructions) 3 9 (3 device x 3 op) 4 7 Device settings: Measurement mode EGNOS DOP Nb of satellites Buffer, m Stop and go/continuous (1s) Yes Max PDOP: 5 Min 4 0,75

12 Kick-off 2010, Ispra, April / 24 Test parcels in Slovenia 7 parcels (3 with trees) Area: 0,1-1ha

13 Kick-off 2010, Ispra, April / 24 Input needed by JRC for reviewing MS test 1. If statistical analysis is to be made by JRC, MS should send: A technical report with the following information Type and number of devices tested Software/Firmware version Method of measurement (vertex/continuous) Device settings (elevation mask, max DOP, etc.) Use of differential correction and type of correction Number of sets, repetitions per set, parcels (with trees), list of operators Sketch of the test parcels on orthophoto and photos of the parcels Data A copy of the measurement protocol (parcel id, date and time, set, repetition, operator, direction of measurement, area, perimeter measured) An excel sheet with the measurements The shp files and LPIS ortho-images of the area

14 Kick-off 2010, Ispra, April / 24 Input needed by JRC for reviewing MS test 2. If statistical analysis is made by MS and is to be validated by JRC -> MS should send technical report data sheets with the statistical analysis

15 Kick-off 2010, Ispra, April / 24 DGPS (code) vs VRS4km (carrier phase) 2nd test Purpose 1. Comparison between a code phase and a carrier phase differential correction of the GPS signal and their influence on area measurement 2. Continuation of the test in vertex mode (in 2009 test performed only in continuous mode) Through local provider of differential corrections: GPS Lombardy (

16 Kick-off 2010, Ispra, April / 24 Design of experiment Trimble Geo XH receiver One parcel inside JRC, 4 modes tested and compared: 1. DGPS - differential code corrections (meter accuracy) in continuous mode 2. DGPS - differential code corrections (meter accuracy) in vertex mode 3. VRS4km - carrier-phase correction via Virtual stations (decimetre accuracy) in continuous mode 4. VRS4km - carrier-phase correction via Virtual stations (decimetre accuracy) in vertex mode

17 Kick-off 2010, Ispra, April / 24 Test field 2 operators 2 days 6 sets (3x2op) 4 repetitions (2 cw and 2 acw)

18 Kick-off 2010, Ispra, April / 24 GPS tracks and measured areas 1/2 (Code) DGPS - continuous Measurement mean and range, sqm Receiver GeoXH+DGPS, Field B, cont : level Date of measurement 5 6 accepted data outlier data overall mean True_value DGPS - vertex Measurement mean and range, sqm Receiver GeoXH+DGPS, Field B, vertex : level accepted data outlier data overall mean True_value 1550 Date of measurement

19 Kick-off 2010, Ispra, April / 24 GPS tracks and measured areas 2/2 VRS - continuous Measurement mean and range, sqm Set 1 Receiver GeoXH+VRS, Parcel B, cont : level Set 3 Set 5 Set 4 Set 2 Set 6 Date of measurement accepted data outlier data overall mean True_value Higher variability in measured area VRS - vertex Measurement mean and range, sqm Set 1 Receiver GeoXH+VRS, Parcel B, vertex : level Set 2 Set 5 Set 3 Set 4 Set 6 accepted data outlier data overall mean True_value 1600 Date of measurement

20 Kick-off 2010, Ispra, April / 24 Tree canopy influence (vertex mode) Trees 80 cm 90 cm DGPS VRS 75 cm Open horizon 10 cm

21 Kick-off 2010, Ispra, April / 24 Statistical tests Outlier detection -> the data is free of outliers (only strugglers were found but kept) According to the analysis of variance the factor direction is significant for operator 1, VRS, continuous mode The direction effect is omitted -> in terms of area is negligible 0,2 0,15 ANOVA Mean difference as error on perimeter between cw (5cm) and acw (-5cm) -> 10cm error_on_perim 0,1 0,05 0-0,05-0,1 acw Direction cw All Pairs Tukey-Kramer 0,05

22 Kick-off 2010, Ispra, April / 24 Results The overall reproducibility limit of the area measurements, expressed as a buffer on perimeter: Trimble GEO XH VRS DGPS R limit - cont 0,25 0,26 R limit - vertex 0,16 0,23 Comparison with the test done in 2009: - Standalone mode - DGPS (code) - VRS (carrier) Buffer, m 0,6 0,5 0,4 0,3 0,2 0,1 0 Std alone Standalone Code 2009 Phase Code Phase 2010 DGPS-2009 VRS-2009 DGPS-2010 VRS-2010 continuous vertex

23 Kick-off 2010, Ispra, April / 24 Conclusions Carrier phase differential correction does not improve significantly the accuracy of area measurement in comparison with code correction Use vertex mode with carrier phase differential correction Both types of differential corrections improve accuracy of area measurements in comparison with standalone accuracy: buffer category goes from 0.75m to 0.50 m

24 Kick-off 2010, Ispra, April / 24 Reminder on GPS validation tests Pay attention to: Direction effect ->special care to the protocol Include parcels with trees on the border You need 2-7 days and 2-6 operators Do not hesitate to ask us for: Review of test protocol and plan Statistical analysis of the data Review of the whole test (if analysis of data made by MS) Thank you