Shanker KC

34 Questions 19 Answers 0 Followers

Questions related from Shanker KC

How to achive transformation from ITRF2014 to ITRF2020 using transformation parameters available in IERS website?

I have 3D position of few of GNSS stations obtained from AUSPOS service in ITRF2014 frame. I have 3D position of same stations from CSRS-PPP service in ITRF2020 reference frame. I want to...

27 April 2024 2,455 3 View

What information can one infer from gravity gradient?

A gravity gradient is different than an absolute gravity value. What is the interpretation of horizontal and vertical gravity gradient?

22 January 2024 8,587 7 View

Why gravity anomaly changes from negative in northern indian plainland to positive in Himalayas and Tibetan plateau?

Below I have added EGM2008 gravity anomaly plot. The gravity anomaly switch its direction from negative in north of India to positive in Himalayas and Tibetan plateau. Why is this happening? What...

01 January 2024 6,282 11 View

How does one go from discrete data points to gridded data points?

How do I obtain gridded data points from discrete data points as shown in following figure?

15 December 2023 8,360 1 View

What does it mean by long-wavelength part, medium-wavelength part, and short-wavelength part of gravity field?

Long-wavelength, medium-wavelength, and short-wavelength information of gravity field, what are these? What part of earth give rise to such different wavelength information?

29 August 2023 3,746 3 View

What makes earth's pole not to be stationery? and how?

I am having difficulty understanding the polar motion of the Earth. I am trying to understand terrestrial coordinate systems in geodesy. Then, there is idea of Conventional International Origin...

23 August 2023 3,194 2 View

Where can I download multi-GNSS precise orbit products?

In IGS website, only GPS precise orbit is available. I want to perform PPP analysis with multi-GNSS combination which requires precise orbit of other constellations along with GPS orbits. How can...

31 May 2023 7,619 5 View

What is the minimum amount of observation period to perform precise point positioning (PPP) in RTKLIB software?

We are trying to perform PPP analysis for 1h observation period. Is 1h of data sufficient for doing PPP analysis?

06 May 2023 9,054 2 View

How can convert rinex 3.04 to other version of rinex?

I have got rinex observation file of rinex version 3.04. But I needed to convert it to rinex 3.02 so that rtklib can take it as input. I checked the website of rtklib, it seems, rtklib can only...

02 April 2023 8,494 2 View

What is vertical datum?

What does vertical datum refer to? Is it Mean Sea Level (MSL)? Is it a zero mark in the tide gauge? Is it some other height value than zero, far from the tide gauge? Is it one reference benchmark?...

16 March 2023 1,036 3 View

Why "we don't we have sufficient knowledge about the density structure of the entire Earth"?

I am reading text on physical geodesy. It says, we can not compute the gravity potential directly because we don't have sufficient information of density structure of the Earth. Why is so?

10 March 2023 4,804 2 View

What is quasigeoid?

Geoid: there are infinitely many level surfaces (equipotential surfaces) and the one which coincides with MSL is called a geoid. But what is the quasigeoid?

10 March 2023 2,585 1 View

Is there any video lectures on 'Gravity Field of the Earth' explained with geodesy perspective?

I am reading through 'Gravity Field of the Earth' chapter of geodesy text book. Of course, its difficult to understand for me, is there any video lectures on this topic?

23 February 2023 3,567 3 View

How can I compute orthometric height from geopotential difference using Helmert's hypothesis?

I have determined the geopotential difference between two stations. Now I want to compute the orthometric height difference between these two stations using Helmert's height formula. But I am...

05 February 2023 5,426 2 View

How precisely we can determine the ionospheric delay in GNSS positioning?

What is the range of values of ionospheric delay and its uncertainty in GNSS positioning?

22 January 2023 4,204 5 View

Is there any python implementation of vmf1 grid?

In vmf data server https://vmf.geo.tuwien.ac.at/, there is fortran and matlab source code to interpolate vmf1 at given location using 2.5o x 2o grid data. I needed that source code in python...

10 January 2023 2,314 1 View

Can you please explain me what is the meaning of these 4 directories?

I enter to: https://vmf.geo.tuwien.ac.at/trop_products/GRID/2.5x2/VMF1/ and I got the following 4 directories: STD_FC/ STD_OP/ VMF1_FC/ VMF1_OP/ What is the meaning of each directory?

07 January 2023 174 2 View

What are the input and output of Vienna Mapping Function(VMF)? How can I get tropospheric delay from VMF?

How can I determine tropospheric dealy at give location (latitude, longitude, height) from VMF? How can I access VMF using python?

06 January 2023 9,758 8 View

How does ionospheric-free linear combination eliminate ionospheric effect from GNSS measured range?

How does this ionospheric-free linear combination work?

21 November 2022 8,731 1 View

Why did the RMS of u-d component for "combined" filter type is highly improved compared to that for "forward" filter type in PPP Static in RTKLIB?

I performed PPP static in RTKLIB in "forward" filter type and then did same in "combined" filter type keeping all other options in both approach. I checked the RMS of u-d component for both...

17 November 2022 8,340 0 View

How did geodesist define/determine/observed the direction of the earth's axis rotation?

How people infer the direction of earth's axis rotation because its invisible. How did they observe the earth's axis of rotation, how did they define and determine this axis?

14 November 2022 9,045 10 View

How did geodesist find/determine position of the equatorial plane?

If i happen to be at equatorial line, how do I know I am at zero degree latitude?

14 November 2022 3,455 5 View

How do I compute gravity anomaly, geoidal undulation, deflection of vertical, and geopotential at any point on the Earth surface from EGM2008 model?

Madar Datum Station (MDS) is one of the height datum stations of Nepal. We have position of MDS in ITRF2014 from GNSS. Being datum station, it has a height above Indian MSL derived from precise...

04 November 2022 319 4 View

What does it mean by tide free geoid model?

GEOID2022 of the USA follows the "tide free" tide system. I want to understand how the geoid model will be tide-free.

26 October 2022 2,132 3 View

Is it possible to process multiple days GNSS CORS data using RTKLIB in PPP positioning mode?

I have downloaded the 7 days GNSS observation data from one of the UNAVCO listed CORS station. So there are 7 different 24h files for each day for the same CORS station. Can I perform PPP in...

30 August 2022 9,804 1 View

What are the reasons behind convergence time period for PPP?

In precise point positioning (PPP) mode, the smooth positioning is obtained after only certain period, which is called convergence period? What causes for convergence period?

30 August 2022 4,130 1 View

How does PPP Static differ from PPP Fixed from PPP Kinematic?

Inside RTKPOST software, there is various positioning modes available. Among, three are: PPP Static, PPP Fixed, & PPP Kinematic. How is one different from another?

30 August 2022 7,352 2 View

Can I process multiple baselines at the same time in RTKLIB either in Kinematic mode or in DGPS/DGNSS mode?

Till now, I have only processed single baseline (One base - one rover) in RTKLIB in Kinematic or DGNSS mode. Can I process multiple baselines (e.g. One base - two rover) in RTKLIB? If so how can I...

30 August 2022 3,564 2 View

What is the modern international gravity datum after IGSN71?

IGSN71 is the international gravity datum defined in 1971. Is there any updated modern international gravity datum that replace IGSN71?

07 August 2022 6,421 5 View

What does the each pixel of SLC product from S1A represent, slant range or ground range?

The spatial resolution quoted in SLC images of S1A, is it the slant range resolution or ground range resolution?

27 April 2022 2,076 0 View

How do I compute the height of tallest skyscraper of Wuhan (Wuhan Greenland center) from S1A images using radar geometry?

26 April 2022 1,734 3 View

Which is more accurate, the ellipsoidal height from SLR or GNSS?

Satellite Laser Ranging (SLR) and Global Navigation Satellite System (GNSS) both measure the ellipsoidal heights. Which measurement of ellipsoidal height is more accurate?

17 February 2022 7,463 2 View

What does it mean GOCE aims to provide precise geoid information globally with 1-2 cm accuracy at a spatial resolution of about 100 km?

GOCE aims to provide precise geoid information globally with 1-2 cm accuracy at a spatial resolution of about 100 km.

11 December 2021 1,526 3 View

How does one compute gravity anomaly when gravity is observed at place which is below MSL?

Gravity reduction for gravity measured at topography below MSL.

21 November 2021 1,517 3 View