Terrestrial, Airborne and Satellite Gravimetryissge.ir/uploads/files/Taft/Hatam.pdf · - GPS...

Terrestrial, Airborne and Satellite

GravimetryY. HatamY. Hatam

- Terrestrial Gravimetry:

Absolute Gravimetry: FG-5, A10

National Absolute Gravity Network of Iran (NAGNI09)

Relative Gravimetry: CG-3/M, CG-5,

Multi-purpose Network (MPGGNI10),

National Gravity Calibration line (NGCLI10)

Damavand Gravimetry Profile

Digital Zenith Camera (DIADEM)

- Airborne (shipborne) Gravimetry: S124b L&R

- Satellite Gravimetry: CHAMP, GRACE, GOCE

New Gravimetric Geoid of Iran (IRGeoid10)

Spatial Resolution: Different G. Systems

Micro-g FG-5

Developping Gravimeters

(precision modification)

National Absolute Gravity Network of Iran

NAGNI09

Objectives:

Reference four other more densed gravity networks

(1st, 2nd , 3rd orders)

Opportunity of studying the variations inter-annuals at two sites

(Tehran et Alborz)

Specifications: Station distribution 300 km

Precision better than 5 µGal

Astara

Birjand

Chalous

Cheshmeh-shur

Esfahan

Kalaleh

Kandovan

Kermanshah

Lahijan

Low shan

Mashhad

Tabas

Tabriz

Teheran Abali

Yazd

35° N

40° N

2000

2500

3000

3500

m

Distribution of Absolute Gravity stations (NAGNI09)

Topogrphical Map

of Iran

Ahvaz

Bandar Abbas

Bushehr

Chabahar

Kerman

Laar

Shiraz

Yazd

Zahedan

45 ° E 50° E 55° E 60

° E

25° N

30° N

0

500

1000

1500To transfer FG-5

24 Measuring Stations

Approximately 40 Measurements

Measuring Absolute Gravity by FG-5

Measuring the couples ’’position - time’’ of an object in free-fall

Calculating the acceleration of the object =>

Gravity

FG5 228

2 23 40 0 0

0 0 0 0

( )1 1, .

2 2 6 24

i i ii i i i i

g t x t x xx x v t v t g t t t

c

γγ γ

−= + + + + + = −

% %% % % %

Measurement procedure

One fall

-5

0

5

10

15

20Cumulative Mean: 979095237.12 µGal +/- 0.71 µGal

µG

al

One hourly Measurement:

120 Falling of the object

Dispersion: 5.56 µGal

-20

-15

-10

15:00Sat 7 Oct 2006

18:00 21:00 Sun 8 3:00Time

16 hours of measurements

⇒16 * 120 fallings

Final Dispersion: 0.71 µGal

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 250

1

2

3

4

5

Station Number of Absolute Gravity points

Set

Scatt

er(

µG

al)

a)

Precision of the Absolute G. Network NAGNI09

Uncertainty of the

measurement

Noise of

the wavesSite in

altitude

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 254.25

4.3

4.35

4.4

4.45

4.5

Station Number of Absolute Gravity points

Tota

l U

ncert

ain

ty(µ

Gal)

b)

Total Uncertainty

Systematical

Error

Set up ErrorMeasurement and Total

Uncertainties of the

NAGNI09 network

Interannual variation of the Gravity in Iran: at

Tehran (NCC)

NCC

Significant Inter-annual

Decreasing of absolute gravity

Regional Hydrological Component (GLDAS et ECMWF, cf. J. P. Boy)

Inter-annual Decreasing : -0.4 µGal/anGPS height variation

Decreasing not explained by GPS or

Regional hydrological Models

Inter-annual Variations of the gravity in Iran

Tehran (NCC)

Estimated Porosity by the gravity measurements: between 2 and

12 %

Estimated Porosity by the pomping: App. 10 % (Engalenc, 1968)

Good Correlation with the height of water

level of the wellsPlate Effect / porosity


Abali (Alborz Chain)

Decreasing -0.76 ±±±±0.30 µGal/an

ABALI

Regional Hydrological Variations

0.28 à -0.35 µGal/an (GLDAS et ECMWF)

Decreasing not

explained by Regional

hydrological Models

Residual Slopes:

-0.99 ±31 µGal/an (GLDAS)-0.30 ±38 µGal/an (ECMWF)� Vertical Movement

� With tectonic origin


Abali (Alborz Chain)

Vertical Speed:

The continental lithosphere

�� Elastic Plate

ECMWF: between 1 ±1.26 mm/an and 1.6 ±2.00 mm/an

GLDAS: between 3.3 ±1.03 mm/an and 5.2 ± 1.63 mm/an

Multi-purpose Physical Geodesy and Geodynamic

Network of Iran (2005-8) (MPGGNI10)

Objectives

– Densification of the absolute gravity network (0 order) by the 1-st

order gravity network

calculating locally the geoidal undulation

Specifications:Specifications:

- Measuring relative gravities each 55 km, with a precision of the order

of 10 µGal

- GPS geodetic height determination with a precision of the order of 1-3

cm

- Precise levelling Height determination with a precision of the order of

Opportunity

– Study of the Geodynamics and Crustal structure of Iran

30° N

35° N

40° N

Region of study

Old g in land

g at 1 st levelling

g at Sea

data5

data6

Land boundary

Sea boundary

Pre-existed gravimetric measurements

45 ° E 50° E 55

° E 60

° E

25° N

Distribution of the pre-existed gravities BGI)

• Land gravity (Green Points)

• At Levelling BMs (Yellow points)

• Sea gravity (red points)

Complete Bouguer Anomaly map (1984)

Completed based on 10 000 gravity data

(Green points)

Not enough measurements for calculation of a

precise geoid

Multi-purpose Network ’’MPGGNI10’’• 600 sites

• 1600 gravimetric

observations

• 1600 working days at

field by 6 gravimètres

Relative Gravimetry ( ) ( )j jij i it St

f S S S j i j iC m m V g g D t t− + = − + −

Ahvaz

Astara

Birjand

Bushehr

Chalous

Cheshmeh-shur

Esfahan

Kalaleh

Kandovan

Kerman

Kermanshah

Lahijan

Low shan

Mashhad

Shiraz

Tabas

Tabriz

Teheran Abali

Yazd

Zahedan

30° N

35° N

40° N

1500

2000

2500

3000

3500

4000

4500

5000

m

Astara

Chalous

Kandovan

Lahijan

Low shan

Teheran-NCCAbali

Tochal1Tochal2

Tochal5Tochal7

Caspian Sea

36° N

37° N

38° N

1500

2000

2500

3000

3500

4000

4500

5000

m

National Gravity Calibration Lines of Iran

Bandar Abbas

Chabahar

Laar

45 ° E 50° E 55

° E 60

° E

25° N

0

500

1000Cheshmeh-shur

48° E 49

° E 50

° E 51

° E 52

° E 53

° E

35° N

0

500

1000

Old Line

851 mGal

New Line

1154 mGal

Profile of Damavand gravimetry

6- Damavand Summit St.

5610 m

5- Permanent icefall St.

5100 m

4- Climbing house St.4- Climbing house St.

4200 m

3- Goosfandsara St.

3000 m

2- Iraa St.

1700 m

1- ABALI Absolute Gravity st.

3160 m

Polour Permanent GPS Station

2280 m ■

Objectives of Damavand gravimetry

- To obtain minimum gravity value in Alborz mountain

- To extend and modify national gravity calibration line

- To modify the gravity prediction models

- To study the isostasy situation of the highest mountain of Iran

- To modify and control the existed numerical density models- To modify and control the existed numerical density models

- To modify the quality of Geoid

- To establish the control points for the future airborne gravimetry

- To study the geodynamical phenomena (Earthquake, Volcano, …)

- To obtain the correct elevation value of Damavand Summit

( Before= 5671 m , Now= ?)

Damavand Gravimetry Profile + NGCLI10

979,400

979,500

979,600

979,700

979,800

979,900

980,000

980,100

980,200Damavand Summit Gravimetry and Extending the new National Gravity Calibration Line of Iran (TC/L NGCLI2005)

All

Gra

vit

y V

alu

es

in

Ira

n (

mG

al)

Gravity Values (Blue)

Gravity Station (Red)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16978,200

978,300

978,400

978,500

978,600

978,700

978,800

978,900

979,000

979,100

979,200

979,300

Damavand Abshar PanahGah Gosfand Ira Abali TochalS Tochal7 Tochal5 Tochal2 Tochal1 NCC Lowshan Lahijan Astara

Summit Yakhi Sara

All

Gra

vit

y V

alu

es

in

Ira

n (

mG

al)

Misclosure Errors of the triangular gravity loops

Error < 50 µµµµGal

40

60

80

100

120

40

60

80

100

120

Uncertainties of the relative gravity measurements

and of the gravity values

-0.04 -0.03 -0.02 -0.01 0 0.01 0.02 0.03 0.040

20

mGal0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.02 0.0220

20

mGal

Histogram of the residuals of the relativegravity measurements

Histogram of the precisions of the gravities

Errors at measurements and at gravity of

the MPGGNI10, of the order of 10 µµµµgal

Permanent GPS Network + IGS

Precision for the GPS height : 1 cm

National GPS and Precise Levelling Networks

1st order

2nd order

Precision for the GPS height : 1 cm

GPS Measurements at 55 km Network (duration 24h)

Precision for the GPS height GPS: 1-3 cm (treated GAMIT)

National Precise Levelling Networks

Precision of the levelling: 3mm km

Transportable Zenith Cameras

(TZK1 , TZK2 , TZK3)

1976, 2000, 1986

Digital

Zenith

Camera

TZK2-D

(DIADEM)

20062006

Airborne

Gravimetry

(Shipborne G.)

GRACE (Gravity Recovery and Climate Experiment)

16 Mars 2002 – for 5 years NASA + DLR

2 Satellite, 200 km distance,

Polar orbit: 480 km

Precision N: 1 cm for 300-400 km, Monthly N

CHAMP (CHAllenging Minisatellite Payloadfor geoscience and application)

15 July 2000

Polar orbit

Altitude: 400 km

Constantly positioned by GPS

Perturbation analyses:

Precision N: 10 cm for wavelength 485 km

CHAMP

Precision N: 1 cm for 300-400 km, Monthly N

1-st Model: GGM02S, Deg. 160, Resolutin:

125 km (Tapley et al., 2005)

GRACE

GOCE

GOCE (Gravity field and steady state Ocean Circulation Explorer mission) ---- 17 Mars 2009 (ESA)

Orbit heliosyncronizd, Altitude: 250 km

Measure Accelerations by 6 accelerometers, 50 cm apart,

Tensor of the gradients (9 elements) and 6 are independent

Precision: 1 cm for wavelength 100 km

Geoid computation

Objective :

Calculation of a new gravimetric geoid model with high

precision - resolution

Method:

Remove - restore + Helmert Condensation

1-D FFT (Haagmans, 1993)

Reference surfaces and heights

N=R

4πγ∆gS(ψ)dσ

σ∫∫

N(Geoid) = h(ellipsoidal) – H(orthometric)

Earth Surface

Geoid

Ellipsoid

Ellipsoidal height

Geoidal Height

Orthometric Height

SRTM topographical Data over Iran

Distribution of gravity data over Iran

Free air Anomaly

∆gFGeopotential Model

∆gGGMDTM

∆gRTM

∆gres = ∆gF - ∆gGGM - ∆gRTMAtpoin

ts

Gravimetric Geoid Computation by remove-restore + Helmert C.

Interpolation

N = Nres + NGGM + NI

∆ggeoidres NresStokes

At

gri

d

Free air Anomaly

∆gF


Free air Anomaly


∆gGGMDTM

∆gRTM


ts

Interpolation



At

gri

d

Statistics of different Global Geopotential Models (GGMs)

At the points GPS / nivelés

Geopotential Model

∆gGGM

Geopotential Model

∆gGGM

Calculated by using the model GOCO01SEGM08(360)