slide applications of gnss pro software for processing gnss short baseline networks in vietnam

APPLICATIONS OF GNSS-PRO SOFTWARE FOR PROCESSING GNSS SHORT BASELINE NETWORKS IN VIETNAM Lau Ngoc Nguyen 1, Huong Thanh Thi Nguyen 2, Hoa Ha Minh 2 1 Department of Geomatics Engineering

APPLICATIONS OF GNSS-PRO

SOFTWARE FOR PROCESSING GNSS SHORT BASELINE NETWORKS IN

VIETNAM

Lau Ngoc Nguyen (1), Huong Thanh Thi Nguyen

(2), Hoa Ha Minh (2) (1) Department of Geomatics Engineering, Ho Chi Minh City University of Technology, Vietnam

(2) Vietnam Institute of Geodesy and Cartography,

Vietnam

14TH CONFERENCE ON SCIENCE AND TECHNOLOGY

• Research on processing GNSS baselines less than 20 km is important for building surveying control networks

• Short baseline networks allow to use single

frequency receivers with cost much lower than dual ones

• All GNSS processing software using in Vietnam are from abroad such as GPSurvey, TGO and TBC from Trimble (USA), LGO from Leica

(Switzerland), …

• We established GNSS-Pro – the first GNSS

processing software made in Vietnam

MAIN FEATURES OF GNSS-PRO

Single baseline processing

Network adjustment

Report

Display and

links

GNSS

data Import

Seting

up

SINGLE BASELINE PROCESSING

• Process single baseline using triple

differenced carrier phase measurements

• Repair cycle slips for single baseline.

• Process single baseline using double

differenced carrier phase measurements to estimate ambiguities.

• Resolve ambiguity parameters

• Re-process single baseline using double

differenced carrier phase measurements with ambiguity corrections.

SUB-SESSION PROCESSING

METHOD

Final solution X

Cycle slip

Sub-session 1

X1

Sub-session 2

X2

Sub-session n

Xn Observation

session

SUB-SESSION PROCESSING

METHOD

• Divide a data session into some sub-sessions

• Process each session separately to have

sub-session solutions

• Combine sub-session solutions into the final solution

Advantages:

• A cycle slip, if it exists, only affects a sub-session, and does not affect the remaining sub-sessions.

• Ionosphere and multipath can strongly affect some sub-sessions; whereas other sub-sessions are hardly affected.

• Exploitation of LAMBDA advantages and the redundancy of a number of GPS and GLONASS satellites help in the ambiguity resolution of each sub-session

• The final solution computed from all sub-session solutions gives results with greater reliability.

EXPERIMENTS ON REAL GNSS DATA

• Hai Duong cadastral network includes 67 baselines ranging from 2.2

km to 11.3 km

• Session length is approximately 1.5 hours Some centered at 14h local

time, strongly affected by the ionosphere

• Many site locations have obstructions, strongly affected by the

multipath and limited number of observed satellites

PROCESSING BY GNSS-PRO

Measurements Carrier phase L1

Elevation cutoff angle 10

Tropospheric estimation No apply

Satellite ephemerides Broadcast

• All single baselines are fixed with centimeter accuracy

level.

• All relative misclosures are less than 10ppm

PROCESSING BY TBC

Software Baseline N E U

GNSS Pro

-GAMIT

DC13-DC16 -0.021 -0.006 -0.058 DC13-DC17 -0.028 -0.001 -0.081 DC12-DC20 -0.043 -0.057 0.055 TBC - GAMIT DC13-DC16 -0.018 0.303 0.088

DC13-DC17 -0.035 0.331 0.103 DC12-DC20 -0.030 0.071 0.042

PROCESSING BY LGO

• LGO does not give all fixed solutions as TBC.

• There are 6 float baselines Compared with GNSS-Pro, deviations are several decameters.

• The fixed baselines give allowable

deviations when compared with GNSS-Pro.

For Hai Dương cadastral network only:

• GNSS-Pro gives fixed solutions for all processed baselines with cm accuracy level

• TBC also gives fixed solutions for all processed baselines with RATIO >2 However, three

baselines have discrepancies > 1dm (absolute) and 10ppm (relative)

• LGO gives 6 float baselines The fixed baselines give discrepancies at the cm level, true to the

nature of the fix status

• GNSS-Pro has more advantages on accuracy, reliability and misclosure checking ability

THANK YOU FOR LISTENING