Permanent GPS Stations in Israel as Basis for

Updated Geodetic Network  

Gilad Even-TzurFaculty of Civil and Environmental Engineering

Mapping and Geo-Information Engineering

Technion, Haifa 32000, Israel

Moshe Rozenblum, Einat SalomonSurvey of Israel

1 Lincoln St. Tel-Aviv 65220, Israel

Permanent GPS Stations in Israel, Sept. 2005

17 StationsReceivers: 11 Ashtech Z-XII

5 Leica SR5301 Trimble 5700

Antennas: 9 Ashtech DM5 Leica DM2 Topcon CR41 Trimble DM

Permanent GPS stations in Israel, Sept. 2005

10 stations are situated on stable roof tops

NRIF

Permanent GPS Stations in Israel, Sept. 2005

7 stations have geodynamic monuments

LHAV

The Control CenterThe GPS receivers are connected to a control center, equipped with master and backup servers, through frame relay connections.

The Communication Network

The GPS Data Flow

5 sec sampling rate Data is downloaded in real

time The RINEX data is

gathered into 1-hour interval files and posted on the internet

Operation Manager Software

The network is controlled by the RTD software.

It is based on epoch-by-epoch technology, which enables monitoring any changes in the station coordinates due to deformation and lost qualities.

Permanent GPS Stations in Israel, Sept. 2005

RAMO is the official IGS station in Israel

The data is processed at SOPAC

The data from RAMO and DRAG is also processed at GIBS (GPS-Informations- und

Beobachtungssystem )

The Permanent GPS Stations in Israel are called:

APN

Active Permanent Network

Free 30 sec sampling rate data is available at:

ftp://212.179.112.235

Until recently, the APN network was mainly used for geodetic and geophysical research.

The APN was used less for surveying purposes:

- Short sessions- OTF ambiguity resolution

used - Lack of transformation

between WGS84 and ITM

The APN Network

VRS - Virtual Reference Station

In order to enable GPS surveying over the entire state of Israel with direct connection to the permanent GPS network, VRS technology is applied.

Economically and practically, there is no need to increase the number of permanent GPS stations in Israel.

The VRS is produced by the GEO++ software

User Interface for Receiving Data

Advantages of Using the APN

Uniformity Accuracy

Reliability Simplicity

► In the near future an RTK option will be added to the APN network

► Geodetic datum is a set of parameters and control points used to: ● Define the size and shape of the earth.● Define the origin and orientation of the coordinate systems used to map the earth.

► The datum is the basis for a plane-coordinate system.

► Geodetic datums range from flat-earth models used for plane surveying to complex models used for international applications.

Datum Definition

► GPS positions and vectors are referenced in the WGS-84 datum

► The Israeli coordinate system is referenced in the GRS-80 reference ellipsoid with geodetic projection called:

ITM - Israel Transverse Mercator

Datum Definition (continuance)

x

y

z

dX

dY

dZ

m

R

R

R

Shifts

Scale

Rotations

Transformation parameters describe the relations between two different datum systems.

7 Parameter transformation:

Datum Transformation

'84 '84 '84 80 '84

'84 '84 '84 80 '84

'84 '84 '84 80 '84

1 0 0 0

0 1 0 0

0 0 1 0

X WGS WGS WGS GRS WGS

Y WGS WGS WGS GRS WGS

Z WGS WGS WGS GRS WGSX

Y

Z

dX

dY

V X Z Y X XdZ

V Y Z X Y Ym

V Z Y X Z ZR

R

R

The set of transformation parameters is determined by a least-squares solution:

Datum Transformation (continuance)

► Each point from the APN network was connected by GPS observations to the nearest 1st order control points. ► A local datum transformation was calculated in order to assign plane coordinates to each permanent GPS station.

The Plane Coordinates of the APN Points

The accuracy of the coordinates is equivalent to the accuracy of the classical 1st order

control network (~10cm)

Permanent GPS Network

A permanent GPS-based network is obviously more accurate, reliable and homogenous than a

classical network.

Permanent GPS Network

Supreme Network

A set of coordinates that was valid for GPS day 275 of the year 2004 (October 1st , 2004) in the ITRF2000 coordinate system was set as the fixed coordinates set for the permanent GPS stations

New Datum for APN

This set of coordinates defined a new datum for APN, called

IGD05

Israel Geodetic Datum 2005

Horizontal residuals resulting from the seven parameters transformation between the ITRF2000 (IGD05) datum and the

Israel Grid datum

5cm

50km

ScaleNetwork:

Residual:

A new set of plane coordinates were adopted for the APN points.

New Datum for Israel Grid

The new coordinates defined actually new datum for the Israeli Grid called:

IG05

Israel Grid 2005

The adopted plane coordinates is a result of similarity transformation between two datums (IGD05 and

IG05) which supplied practically zero residuals in the least-squares process.

Official 7 Parameters Transformation

IGD05

IG05

Calculate official 7 parameter transformation between the two systems

A flow chart for calculating new control points in IG05 coordinate system

Measuring methods for establishnew control point

1. Relative to APN station

2. Relative to VRS

3. Relative to base station

4. Geodetic network

Field Work Guidelines

► Two independent Observation sessions

► Observation sessions of at least 10 min

► Time duration between two sessions of at least 60 min

1. Measuring relative to APN station

10km

TELA

First session:

10min 10min

10min

10min

TELA

10min

10min

10min

Time duration between sessions – 60 min

1. Measuring relative to APN station

Second session:

5km

VRS1

10min 10min

10min

10min

2. Measuring relative to VRS

First session:

VRS2

VRS1

VRS3

The distance between two VRS should be at least 120m

10min

10min

10min

Time duration between sessions – 60 min

2. Measuring relative to VRS

Second session:

VRS2

VRS1

VRS3

Measured vectors:

2. Measuring relative to VRS

► Connect the base station to IGD05 system 10km

BASE

90min

IGD05

IGD05

3. Measuring relative to base station

BASE

10min 10min

10min

10min

IGD05

IGD05

► Measuring new control points

First Session:

3. Measuring relative to base station

BASE

10min

10min

10min

ILGD05

ILGD05

3. Measuring relative to base station

► Measuring new control points

Second Session:

Time duration between sessions – 60 min

Assume work with 3 receivers

1

IGD05

IGD05

2

3

4

- Sessions of at least 10 min- Each new point should be measured in two independent sessions

4. Measuring Geodetic Network

The Geodetic-Geodynamic Network (G1)

► Includes 160 points that homogeneously cover the state of Israel

► The location of the points was determined mainly according to geological considerations

►The points were built according to very high technical specifications, to ensure their geotechnical stability

The goal of the Geodetic-Geodynamic Network

► A potential geodetic network for monitoring deformations in primary and secondary known faults

► Serves as the major geodetic control network of Israel

The Measurement Campaigns► During 1996 the G1 network was measured for the first time (Blue circles and Red squares)

► The second campaign was held in 2002

► Only 100 points were measured (Blue circles)

► 5 new points were fixed in the northern part of the network (Yellow circles )

► 11 continuous permanent GPS stations were operated (Green triangles)

► the accuracy of the points is better than 1cm

The G2 Network

► Abut 1000 points that organized in closed loops

► Most of the points are BMs from the Israeli vertical control network

► The points were measured during long period and not as one campaign

► The network accuracy is not homogeneous and not satisfactory (~5cm)

Vertical Control

► Survey of Israel (SOI) decided that the future vertical control in Israel will be based on ellipsoidal heights instead of orthometric heights

► SOI will support and maintain spatial geodetic network which will serve as horizontal and vertical control

► The APN and G1 will be used as basis for ellipsoidal vertical control

► Undulation model will be used to convert ellipsoidal heights to orthometric heights