Transcript Document

Permanent GPS Stations
and their Influence on the
Geodetic Surveys in Israel
Gershon Steinberg
Survey of Israel
1 Lincoln St. Tel-Aviv 65220, Israel
Gilad Even-Tzur
Mapping and Geo-Information Engineering
Technion, Haifa 32000, Israel
(consultant to SOI)
Permanent GPS Stations
in Israel, October 2006
 18 Stations
Receivers: 7 Ashtech Z-XII
6 Leica SR500
5 Leica 1200 PRO
Antennas: 9 Ashtech DM
6 Leica DM
2 Topcon CR4
1 Trimble DM
Upgrade to GLONASS is coming up soon
Permanent GPS Stations
in Israel, October 2006
 11 stations are situated on
stable roof tops
NRIF
Permanent GPS Stations
in Israel, October 2006
 7 stations have geodynamic
monumentation
LHAV
The Control Center
The GPS receivers are
connected to a control
center, equipped with
master and backup
servers, through IPVPN
connections.
The Communication Network
The GPS Data Flow
 1 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.
Permanent GPS Stations
in Israel, October 2006
 RAMO is the official IGS
station in Israel
 All the data is processed at
SOPAC (Scripps Orbit and
Permanent Array Center)
 The data from RAMO and
DRAG is also processed at
EPN (EUREF Permanent Network)
The Permanent GPS
Stations in Israel are
called:
APN
Active Permanent Network
The VRS and RTK Options
In order to enable GPS surveying over the entire
state of Israel with direct connection to the
permanent GPS network, VRS and RTK
technologies are applied.
The VRS and RTK are produced
by the GEO++ software
The Plane Coordinates of the APN
Points
► Each point from the APN network was
connected by GPS observations to the nearest
1st order control points.
► A local datum transformation (3D) was
calculated in order to assign plane coordinates to
each permanent GPS station.
The accuracy of the coordinates is equivalent
to the accuracy of the classical 1st order
control network (~6cm)
Permanent GPS Network
A permanent GPS-based network is obviously
more accurate, reliable and homogenous than
the classical network.
Permanent GPS Network
Supreme Network
New Datum for APN
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
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
Israeli Grid
Scale
Network:
50km
Residual:
5cm
New Datum for Israel Grid
A new set of plane coordinates were adopted for
the APN points by adding the residuals of the
transformation.
The new coordinates defined new datum for the
Israeli Grid called:
IG05
Israel Grid 2005
Official 7 Parameters Transformation
IGD05
IG05
official 7 parameters
transformation between
the two systems
A flow chart for calculating new control
points in IG05 coordinate system
Geodetic Control Networks
• The National Geodetic Control Network will be
defined as 3D control.
• The network is based on the Permanent GPS
stations of Israel (constitute the higher order).
- Primary 3D class G
- Secondary classes:
S: horizontal coordinates .
E: ellipsoidal heights.
Horizontal Control
• The primary objective of the horizontal
control network is to serve the cadastral
surveys.
• The goal is to define the cadastral
boundaries with an accuracy of 5cm (95%).
National Control Network Classification
and Required Accuracy
Vertical Control
Ellipsoidal Control
• There is neither practical possibility nor
actual need to maintain a country-wide
vertical orthometric control network.
• SOI will maintain vertical ellipsoidal height
control network .
National Control Network Classification
and Required Accuracy
Orthometric control
• The transition to ellipsoidal heights only, is
premature yet.
• The orthometric heights will be used as having a
local datum.
• HL can be measured either by geometric leveling,
trigonometric leveling or GPS based on local
benchmarks.
• HS (statutory heights) measured by GNSS and
official geoid undulations model (OGUM).
THE IDEA OF OFFICIAL GEOID
UNDULATIONS MODEL (OGUM) AS A
SUBSTITUTE FOR ORTHOMETRIC
CONTROL
• A very important objective of the leveling network is
to bring consistent identical heights by every surveyor.
• There is no need to wait for the "perfect" geoid model.
• We suggest declaring the best available Geoid
Undulations Model as an Official Model (OGUM).
• The combination of OGUM with vertical Ellipsoidal
Control based on CORS, produces a practical countrywide network of Orthometric Height Control,
appropriate for most of the geodetic/surveying needs.
Vertical Local Orthometric Control Networks
Levels and Required Accuracy
•
•
•
•
New: D is the horizontal distance.
HL1 and HL2 can be measured by leveling only.
HL3, HL4, HL5 can be measured by GPS also.
E1 will produce HS1 and E2 will produce HS2 .
Experiments In Israel
Goal: To examine the accuracy of orthometric
height differences based on GPS measurements
and OGUM in different locations in Israel.
Two alternatives for OGUM:
1. ILUM1.0 - Israeli Undulations Model, Based
on
750 Benchmarks.
2. GPM98B- Global Geopotential Model (Wenzel),
contains few gravity data from Israel.
Experiments In Israel (cont.)
• Six height-differences (between 4 adjacent
benchmarks) were measured simultaneously
by GPS (40 minutes' sessions).
• The relative accuracy of the known
orthometric height -differences, as well as the
measured ellipsoidal height- differences, is 12cm.
Experiments
In Israel (cont.)
• Eight locations where the
OGUM experiment was
held in Israel.
• The numbers denote the
place's name as appears in
the next table.
Experiments - Results
• The RMS and the mean PPM values of the
differences between the known orthometric heightdifferences and the orthometric height-differences
obtained by GPS and the two alternatives for the
OGUM.
Discussion
For a reasonable orthometric control we actually
need a height-differences accuracy of 25mm for
benchmarks 1km apart: (25PPM).
• We achieved this goal in all our experiments with
the temporary Israeli OGUM. It was achieved
also using the Global model, except for Eilat.
• The results demonstrate the capability of the idea,
for most of the engineering works.
• Not instead of existing good networks.
• A special benefit for areas were establishing a
leveling network is practically impossible.