Hello Abdel,

EMPCOV uses your input data points to derive the empirical covariance function. The empirical covariance function consists of discrete covariance values computed by taking into account points within a specified distance range (i.e. 0-10 km, 10-20 km, 20-30 km etc...).

The COVFIT function fits an analytical covariance model to the empirical values derived from EMPCOV. In general, the analytical covariance model is a function of distance, where its limit approximates zero, as the distance approximates infinity (i.e. exponential, gaussian). The analytical covariance model used in COVFIT is the Tscherning-Rapp.

Regards,

Dimitrios

Dear Dr. Piretzidis

Thanks for adding your answer

I have some questions about EMPCOV and COVFIT

EMPCOV

-The empirical covariance function for the anomalies (Δg) from the RTM-effects have been subtracted file (nmfa-egm96-TC.dat)

- The results should be stored in files named (nmfa-egm96-TC-COFIT(2).txt)

- The question here, where data of empirical covariance for the anomalies (Δg) (blue Curved)

COVFIT

-Gravity error-degree-variances for the EGM96 coefficients (file egm96.edg.) this file may be obtained using the GRAVSOFT program “ degv.for “, which will produce the degree-variances for gravity anomalies. (But, program “degv.for “Does not give the same results that are found in the file egm96.edg.) Why?

-Input convariance model parameters (How can be obtained)

- Finally, where data of analytical covariance for the anomalies (Δg) (red Curved)

Very Thank

Abdel Rahim

Hello.

The COVFIT is search between a set of definite positive functions. The important parameters of COVFIT are:

type (exponential, normal, bessel J0, bessel J1 [2-Dim case],  cos, sinc for [1-Dim case]), more complex COVFIT could be obtain combining  the model: e.g. exp*J0.

correlation lenght

amplitute and exponential terms.

The parameters of COVFIT are found with the "eyes", studing min-max, zero and so on  of EMPCOV. For obtain a positive covariance matrix the COVFIT must be zero to correlation lenght.

 Dr. Crippa

Thanks for adding your answer

Can you send me  more details about  "EMPCOV and COVFIT"

Very Thank

Abdel Rahim

I have no idea what these words stand for.  They sound like names of some computer programs.  Possibly the people above are more knowledgeable, so you should listen to them.

Cheers,

PV

Dear Abdel Rahim

I didn't get your problem with running EMPCOV module, but about COVFIT you should be careful when you input value for "mean lat./long. spacing". You can find the appropriate value in the report file of EMPCOV (empcov.log).

Regards,

Sabah

Dear Ramouz

Thank you  for adding your answer ...

Now  I know use "EMPCOV and COVFIT"

Very Thank

Abdel Rahim