You can try using 'gmt grdsample' module with -T option to translate between gridline node registration and pixel node registration.

Dear Pankaj Kumar, your question is very interesting, and it is triggering another one:

Why do you work in ocean with Bouguer instead Free Air gravity anomaly?

My warning / suggestion is due the possibly errors of your grids or nodes are masked by other effects, such as:

The salinity of the sea and its temperature effect over density. Do you have this data for the reduction? Do you use a constant water density of 1050 kg/m^3? 1030 kg/m^3?

Do you have enough input data for your Bouguer anomaly to fit the results, e.g., slab / Bullard´s correction, curvature Bullard´s correction and terrain Bullard´s correction?

Do you have the precision such as a very fine global relief model? Please, remember this landmark article: Challenges in defining of Bouguer gravity anomaly by Mehdi Goli (Journal of the Earth and Space Physics 40 (2): 97-111):

"One of the most ambiguities in definition of Bouguer effect gravity anomaly arises from formulating the effect of topography. The gravitational of topography can be split into Bouguer term, which is the dominant term, plus minor effect, terrain roughness. In the evaluation of a topographical effect, planar or spherical models of topography can be used. Many studies have shown that planar and spherical model of topography give very different results for Bouguer anomalies."

On the other hand, the last question could be: Do you use the Bouguer anomaly in Exploration or Geodetic application?

Best regards, Mario E. Sigismondi

@priyesh kunnummal yes, I have used grdsample with -T to translate from node registered to pixel registered.

Actually, when I am doing so, the new pixel registered grid file show very little variation in basemap. Suppose, lattitude 5 has been chosen in psbasemap but after it node to pixel lattitude changes from 5 to 4.9999.

Well.. I suppose that you are having a problem when doing the computation part due to the mismatch in the two grids files (gravity & gebco) node locations.

Both the grids should cover the same region. You can try the below code to slightly adjust the region.. It may work. Better consider larger regions and use grdcut to go for smaller one.

gmt grdsample -Rgravity.grd gebco.grd -Ggebco_new.grd -n+c -V

You can post in gmt forum for a quick response.

https://forum.generic-mapping-tools.org/

@Mario Emilio Sigismondi actually I have to calculate the Mantle Bouguer Anomaly of the region thats why calculating bouguer.

I don't have any other data but only satellite bathy and gravity data only. Yes, i have taken water density of 1050 kg/m^3.

I think that there is very minor role of salinity and temperature on FAA, even we don't consider it also.

Ok Pankaj, just let me recommend to you to work with the isostatic residual gravity that efficiently separates gravity caused by near-surface / intra-crustal density inhomogeneities from the large anomalies that effect from the mantle.

A benefit of the isostatic reduction over other methods of regional-residual separation, e.g., wavelength filtering, uwc, is that regional field removed by the isostatic reduction is a consequence of a physical model in which, density contrasts and geometries are completely arranged. Also, your initial model can be changed at any time in your iterative process of interpretation.

Best wishes Pankaj, Mario

@mario emilio sigismondi, thank you very much sir for your kind suggestion, i will surely do that. However, still my question remains unanswered. If you please suggest me some solution for this then that will b more appreciable.