International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 1

Number 2

June 2007

129

Application of GNSS Integrated Technology to

Safety of Inland Water Navigation

D. Popielarczyk & S. Oszczak

University of Warmia and Mazury in Olsztyn, Olsztyn, Poland

ABSTRACT: In the paper the description of some applications of satellite integrated technology, elaborated in

the Chair of Satellite Geodesy and Navigation of University of Warmia and Mazury in Olsztyn, to bathymetric

survey of Great Masurian Lakes is given. The Lake of Sniardwy, the largest lake in Poland with about 11,000

ha has been measured using this modern technology with precise satellite positioning of underwater stones

and shallow waters dangerous for sailors. Next the numerical map was elaborated and edited for sailors,

fishermen and tourists. Some conclusions and recommendation for future works on inland navigation charts

are also given.

1 INTEGRATED NAVIGATION

1.1 Safety on inland water reservoirs

Marine navigation is the process of planning and

controlling the safe movement of boat from one

place to another (Bowditch, N. 2002). The inland

waterways navigation especially includes piloting in

narrow canals, channels, rivers and shallow estuaries

– mostly lakes. Safe navigation can not be done

without actual bathymetric maps, digital bottom

visualization and information about under water

obstacles.

In north – east part of Poland there is situated

Warmia and Mazury region frequently called the

Land of a Thousand Lakes. It is the center of

recreation for tourists from all over Poland and from

abroad. There is an amazing opportunity for sailors

and fishermen. In the summer time there is almost

10,000 sailing boats on the Great Mazurian Lakes in

Poland, carrying 50,000 tourists every day.

Almost all of lakes do not have up-to-date

analogue or digital charts. The most part of them has

been measured almost 50 years go. Existing

analogue maps do not present the real and accurate

bottom surface. Unfortunately many of the

mentioned reservoirs have dangerous for sailors

shallow regions with stones and reefs. The

dangerous places make the inland waterways very

difficult to navigate. Therefore it is very important to

ensure the general safety which could be reached by

creating digital, bathymetric charts, marking the

inland waterways and especially dangerous shallow

stone reefs on inland waterways of Great Mazurian

Lakes.

The team of Chair of Satellite Geodesy and

Navigation of Warmia and Mazury University in

Olsztyn has developed integrated technology of

bathymetry surveying, which makes possible

navigation of the small hydrographic boat along the

pre-defined profiles, examination of bottom shape,

computation of water volume, elaboration of

bathymetric charts and monitoring of dangerous

shallow places.

For the developed Integrated Bathymetric System

a number of professional equipment units are used,

as follows: the EGNOS and DGPS/RTK receivers,

GPRS modems, EA 501 P Simrad single frequency

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digital echo sounder, Imagenex SportScan side scan

sonar, YSI 600R water quality sonde and special

GPS/CAD software.

The hydrographic equipment is mounted on board

of the motorboat. The small but safe and easy to

use hydrographic boat, called “ORBITA”, is used

for raw-data collection during these integrated

measurements. The implemented technology allows

designing of measurement profiles, navigation along

the profiles, recording positions and bathymetric

data, making correlation of these both data and

finally creating digital bathymetric maps. The

developed Integrated Bathymetric System combined

with side scan sonar gives a great chance to study the

underwater environment, especially monitoring

underwater dangerous stones and shallow areas.

The paper presents application of GNSS

integrated technology to monitoring and safe sailing

on Great Mazurian Lakes.

Fig. 1. Lake Sniardwy location

1.2 Lake Sniardwy – the biggest lake in Poland

The most dangerous for sailors is the largest lake in

Poland called Sniardwy Lake with its surface area

over 10,000 ha. The lake is placed in south part of

the Land of a Thousand Lakes (see Figure 1). This

shallow reservoir has bad reputation due to

unexpected strong winds and storms. Thus, inland

waterways should be precisely determined and the

majority of existing underwater obstacles (mainly

stones and very shallow waters), dangerous for

sailors, should be precisely positioned on the

navigation analogue as well as digital charts.

The results of the experiments carried out on the

biggest lake in Poland, Lake Sniardwy, using GPS

receivers working in DGPS/GPRS and EGNOS

mode will be presented. Differential GPS satellite

measurements were based on the GPRS data

transmission system, originally developed in the

Chair of Satellite Geodesy and Navigation, of

Olsztyn University (Oszczak, B. & Oszczak, S. &

Ciecko, A. 2004).

2 GNSS INTEGRATED TECHNOLOGY

2.1 Integrated Bathymetric System

The research team of Chair of Satellite Geodesy and

Navigation has developed the integrated technology

of bathymetry surveying in order to examine under

water environment (Popielarczyk, D. & Oszczak, S.

2001). The developed Integrated Bathymetric

System basically consists of (see Figure 2):

− The GNSS positioning system

− The bottom detection system

− The special GPS and CAD software.

2.2 GNSS equi pment

The Differential GPS positioning system uses two

Ashtech Z-Xtreme GPS receivers. The first of them,

placed at a known mark is a stationary receiver

called base or master reference station. There can be

used the permanent reference station or a local

station set up only for the dedicated project. The

base station receiver determines the errors of

measurement data between fixed and observed

station position (corrections). The DGPS corrections

in RTCM v. 2.2 format are sent via GPRS (General

Radio Packet Services) to the rover GPS receiver in

unknown location and can be applied to

measurement data.

The results of our experiments and analysis of

accuracy of boat positioning during bathymetric

survey show that the comparison of the phase OTF

mode horizontal position with coordinates obtained

in real time code Differential GPS show differences

from -0.95 m to 1.05 m for dB and dL (Popielarczyk,

D. & Oszczak, S. 2002). According to IHO

Standards for Hydrographic Surveys, where the

horizontal accuracy for Special Order reservoirs is 2

m, achieved accuracy is sufficient for majority of

bathymetry surveying.

Fig. 2. Integrated Bathymetric System

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2.3 Hydrographic system

The hydrographic equipment includes EA 501 P

Simrad single frequency digital hydrographic echo

sounder, Imagenex SportScan Side Scan Sonar and

YSI 600R sonde for water quality sampling.

The EA 501 P system basically consists of

transducer, transceiver and personal computer. The

collected data are processed on-line for generation of

colour echograms and tables.

The echogram is presented on the Laptop display.

The file system allows recording selected data for

further analysis. Sample data may also be stored on

hard disk and replayed for demonstration of survey

echo data. A navigation receiver can be connected to

the Laptop serial port (NMEA-GLL format), and

position data can be provisionally combined with the

measured echo data. The EA 501 P Simrad general

specification is as follows: the transceiver 200 kHz

frequency, max. freshwater detection depth – 600 m,

accuracy about 0.25% of measured range, transmitting

power 50 to 250 W, calculation interval for 0 to 10

per second.

The Imagenex SportScan is a dual channel

(2x330kHz), high resolution digital side scan sonar

operated directly from PC computer. The towfish

operates from a standard 12 Volt DC power supply

or boat's battery, and the RS-232 connector plugs

directly from the Kevlar towfish cable into the back

of a PC computer or laptop.

The SportScan software can read GPS raw data

into the PC computer, display it on the screen, and

use the speed over ground to adjust the aspect ratio

of the sonar image. Objects can have their height and

length determined with the click on the sonogram.

All data can also be stored on hard disk for later

display and analysis. The side scan sonar has

maximum operated depth of 30 m and it is used for

underwater objects such as big stones and wreck

localization. The last summer DGPS/SONAR

experiments indicate that the accuracy of underwater

object determination is of order of 1-2 m. Figure 3

shows the same object on the echogram (on the

right) and sonogram (on the left).

The bathymetric system combined with side scan

sonar gives a great chance to study the underwater

environment, and especially to monitor underwater

objects and dangerous stones.

Fig. 3. Under water object on the echogram and sonogram

The YSI 600R provides water quality sampling

for both surface water and groundwater. This sonde

measures temperature, conductivity, dissolved

oxygen, and pH. The speed of sound in water is

estimated by a simple empirical formula (Clay, C. S.

& Medwin, H. 1977). The YSI 600R sonde is also

used for pollution monitoring (Popielarczyk, D. &

Oszczak, S. 2002).

The special GPS and CAD software of the system

allows the measurement profiles to be designed,

enables navigation along the profiles, recording and

combining the positioning/bathymetric data, and

finally creating bathymetric maps. For elaboration of

raw-data the originally developed software Echo

Converter is used.

The Integrated Bathymetric System is mounted

on board of small, but safe and easy to operate

motorboat called “ORBITA”. It is perfectly suited

for raw-data collection during inland water

measurements.

3 SNIARDWY LAKE BATHYMETRIC

CAMPAIGN

3.1 Preparations for experiment

Some of Great Mazurian Lake has its waterways

marked by floating signs and dangerous places by

Cardinal Buoys in IALA (International Association

of Lighthouse Authorities) system. Unfortunately the

biggest reservoir – Lake Sniardwy has not yet such a

system. That is why this lake was chosen to be

examined as the first. The project on the Lake

Sniardwy consists of the following stages:

− DGPS/GPRS permanent and spare local reference

stations configuration

− Designing of measurement profiles

− Hydrographic system calibration

− Bathymetric survey

− Localization of underwater objects

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− Elaboration of measurement raw-data

− Creation of bathymetric digital chart.

3.2 DGPS/GPRS permanent and spare local

reference stations configuration

The permanent DGPS/RTK/GPRS reference station

is situated about 30 km from test area in Gizycko, a

tourist town loated in the very heart of Great Mazu-

rian Lakes. Differential GPS satellite measurements

were based on the GPRS (General Radio Packet

Services) data teletransmission system, originally

developed by the Chair of Satellite Geodesy and

Navigation in cooperation with Biatel Company. The

level of GSM coverage and GPRS service quality in

the specific region of operation (on the lakes) is fully

sufficient for the purpose of the bathymetric surveys.

The DGPS corrections are sent to the rover Ashtech

Z-Xtreme GPS receiver every 3 seconds. In the

surroundings of the project area the backup local

reference station was activated (Ashtech Z-Surveyor

GPS receiver).

Thales Mobile Mapper GPS receiver was also

configured to receive EGNOS corrections.

The measurement profiles were designed on

digital shore map of the lake parallely, every 50

meters one after another.

3.3 Hydrographic system calibration

Before hydrographic sounding the single beam echo

sounder was calibrated. The YSI 600R sonde was

used to determine temperature and conductivity of

the water column from bottom to the surface. The

speed of sound in water was estimated by YSI 2SS

software using Clay and Medwin formula. The mean

value of sound speed was determined to be 1480

m/s. Simrad EA 501 P was also controlled by

conducting bar-check calibration. An average speed

of sound was entered directly into the echo sounder

before data acquisition.

Accurate sensor offsets was measured between

the echo sounder transducer and the reference water

level and then applied within the acquisition system.

The GPS antenna was mounted vertically over the

echo sounder transducer, which was placed in the

hull of “ORBITA” boat. Therefore no horizontal

offsets need to be applied.

3.4 Bathymetric survey

After the data acquisition system had been properly

configured and all of the necessary calibrations had

been completed, on-line data acquisition could

begin. The project was conducted by the team of the

Chair of Satellite Geodesy and Navigation. The raw-

data acquisition process took a lot of time and staff

effort. The total amount of data record time was

approximately 300 hours.

During the experiment, on board of the motor

boat two GPS receivers were installed: Thales

Mobile Mapper in EGNOS mode and Ashtech Z-

Xtreme working in DGPS/GPRS mode. The DGPS

unit was receiving real time corrections from base

reference station via GPRS Cellbox modem. At the

same time the receiver was sending out differentially

corrected boat position to:

− The software ESRI ArcView 8.3, for navigating

along the pre-defined profiles using Laptop

monitor, in NMEA-GGA message format

− The EA 501 P Simrad echo sounder in NMEA-

GLL format.

The memory cards of the base station, rover and

back up station receivers, stored raw observation

data to make possible computation of the boat

positions in post-processing mode.

In the navigation software the position of the boat

was displayed against the background of the digital

shore map on board screen. This allows the

navigation along pre-defined measurement profiles.

During the experiment the profiles were designed

parallely every 50 meters one after another.

Combined position and depth data were saved on

the Laptop hard disk, which was controlling

sounding the hydrographic system also.

The mean local water surface was taken as the

reference water surface during the project. The

kinematic post-processed OTF precise technique was

used to control the hydrographic survey and

adequate ellipsoidal height/water-level relationships

have been developed. The reference water surface

was reduced to the vertical datum in Poland based

on Kronstadt ’86.

3.5 Localization of underwater objects

The measurements on Great Mazurian Lakes

included localization of under water stones and reefs

and other objects also. Two hand held receivers with

ability to achieve EGNOS or DGPS/GPRS

corrections were used to collect over 280 coordinates

of shallow areas and stones on Sniardwy Lake.

The Imagenex SportScan side scan sonar was used

for tests of under water object detection. During

measurements two wrecks were found. One of then

is a wooden ferry sunk in Lake Kisajno. The second

one is a wreck of motorboat in Lake Krzywe (see

Figure 4).

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All collected bathymetric raw data and side scan

sonar data were helpful to identify and elaborate

information about shallow areas for bathymetric map

preparation. That kind of data gives possibility of

creation an Interactive Underwater Surface Object

Base.

Fig. 4. The wreck of motor boat in Lake Krzywe

3.6 Elaboration of measurement raw-data

Hydroacoustic sounding took 31 days of field work.

The total length of boat track sounding was about

2000 km. All collected hydrographic and GPS raw-

data were initially processed and edited in the field

and then recorded for further elaboration.

After field data acquisition was complete, the data

elaboration started. The special software Echo

Converter has been originally developed by our

team. This program can import echograms from

Simrad binary format and export as *.txt file. Bad

depth and coordinates data can be shown, filtered

and stored. Surveyor can take a careful check of the

records to ensure that the digital data accurately

depicts the true bottom. During depth editing, the

digital depth record should be compared to the

analog echo sounder trace. This software is open and

can be enriched of new options for adjusting and

smoothing of survey data.

The Echo Converter includes algorithm, originally

developed by the authors, for the time correlation of

GPS horizontal position and depth data. During

hydrographic measurements the combined position

and depth data are being saved on the Laptop’s hard

disk. Both data sets a short latency. Latency is the

time difference between the recorded time

positioning data and the recorded time of depth

detection. The latency typically depends on the depth

detection frequency and boat speed. While surveying

at slow speed, depth detection frequency is high, and

this shift will be small. At higher speed the

displacement increases, proportionally to the speed.

The results of the experiment show that the

differences of depths range from -0.12 m to 0.13 m,

with the maximum depth of 18.58 m (Popielarczyk,

D. & Oszczak, S. 2003).

3.7 Creation of bathymetric digital chart

During Sniardwy Lake measurement campaign over

600,000 raw-data points were recorded and

elaborated. The surface area of the lake is 10,177.44

ha, length of shoreline is 73,259 km, mean depth is

6.86 m and maximum depth 23.93 m, while the

height of reference water level is 115.94 m (vertical

datum - Kronstadt ’86).

Fig. 5. Lake Sniardwy bottom shape

The bottom surface occurs to be very

sophisticated. In this shallow reservoir there are

many sudden big slopes and faults (see Figure 5).

Some fragments of Lake Sniardwy have no

identified on the old maps steep hills from 6-10 m

depth to very shallow areas of 0.5-1 m with huge

stones. These places are very dangerous for sailors

and motor boats especially during strong wind,

storm and rough water surface.

The actual publication of digital bathymetric map

was elaborated and published in 2006. The new chart

was prepared especially for sailors, fishermen and

tourists with basic information of dangerous stone

reefs, actual shore and reed line, ports and

waterways boys (see Figure 6).

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Fig. 6. Lake Sniardwy bathymetric chart

3.8 Interactive Underwater Surface Object Base

The sailing safety can be partly ensured by elabora-

ting new up-to-date bathymetric charts and marking

the shallow areas by cardinal boys in IALA system.

Moreover, there is a need to creation the Interactive

Underwater Surface Object Base (IUSOB). The main

idea of preparation such a base is to get more

detailed bathymetric raw data of selected shallow

parts of the Great Mazurian Lakes. The aim can be

achieved by collecting information of underwater

objects, especially reefs, big stones, wrecks by using

the side scan sonar, direct under water research

by divers with the use of the DGPS receiver

(underwater GIS) and camera. The collected

information should be professionally elaborated in

order to create Digital Model Terrain presentations

and to prepare three dimensional visualizations.

The concept of creating the interactive www base

site expects users to add their own reliable raw data

to enrich the main base of information.

4 CONCLUSIONS

4.1 GNSS positioning techniques

During experimental measurements EGNOS and

DGPS/GPRS positioning techniques were used.

Dynamic DGPS positioning with the use of EGNOS

corrections shows that the RMS errors achieve max.

10 m. At the same time autonomous horizontal

position accuracy was max. 6.50 m (see Figure 7).

Further long-term static EGNOS and DGPS

analyses shows that EGNOS horizontal errors reach

7.42 m. Parallel working DGPS system based on

LF/MF reference station achieves horizontal

accuracy within 1.72 m (Mięsikowski, M. & Nowak,

A. & Oszczak, B. & Specht, C. 2006). Observed

EGNOS accuracies show, that it can not be used in

dynamical applications before the system achieve

FOC status.

Fig. 7. Dynamic GPS autonomous and EGNOS corrected

position accuracy

4.2 Safe inland water navigation

The low cost and high efficient Integrated

Bathymetric System on board of motorboat called

“ORBITA” has been used for bathymetric

measurements on Lake Sniardwy, the largest inland

reservoir in Poland. Digital bathymetric chart of the

lake was elaborated and published. The next step is

the elaboration digital map to be ready for use in

hand held GPS receivers and echo sounders for

sailors and fishermen.

Having actual and up-to-date chart of the lake the

DGPS/GPRS system provide reliable and precise

satellite navigation service for users, as well as the

precise monitoring service for sailing boats in the

case of emergency, mainly due to the unexpected

strong winds and storms.

Having actual charts the inland waterways should

be physically localized by buoys or by navigation

signs in the case of underwater stones and reefs.

Additionally the preliminary data base (IUSOB)

is currently created, for visualization of dangerous

underwater objects. Within the next few months

further measurements will be taken with the use of

side scan sonar and direct underwater search in order

to collect new information about big stones and

bottom shape. The experimental project covers a part

of Lake Sniardwy.

The Lake Sniardwy hydrographic campaign was

run within the confines of realization scientific

project Project on Civil Protection and Safety

System for Development of Eco-Tourism in Warmia

and Mazury Region with GNSS Applications,

granted by the Ministry of Science and Higher

Education in Poland.

The Interactive Underwater Surface Object Base

is created within the confines of realization scientific

135

project Application of dynamic positionig techniques

DGPS/EGNOS/RTK/GPRS and bathymetric measu-

rements for creation of an Interactive Underwater

Surface Object Base, granted by the Ministry of

Science and Higher Education in Poland.

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