how to convert GRS80 to WGS84?

hello! I have problem with convert GRS80(EPSG:5179) dataset like X=959200, Y=1952800 into

WGS84 lon and lat...

Existing functions(utm2ll or utm2ell) give me wrong lat and lon!

they give me lat:17.448, lon:137.7768 while real answer is lat:37.3315, lon:126.4550

Is there any function for converting meter based GRS80 into lon and lat?

Answer 1

[Purvaja]

Hey @hye wook Kim,

I understand that you need to convert X–Y coordinates defined on the GRS80-based / Unified CS (EPSG:5179) back into geographic WGS84 latitude and longitude, and that existing UTM-based helpers like utm2ll are giving you different results than expected.

The simplest approach in MATLAB is to use the Mapping Toolbox’s PROJ-based functions:

1. Create the EPSG:5179 CRS object with “projcrs”.
2. Invert your X–Y to lat–lon using “projinv”.

Follow the below code regarding execution:

% 1. Create the EPSG:5179 projected CRS object 
p5179 = projcrs(5179, "Authority", "EPSG");  

% 2. Your input X–Y in meters 
X = 959200;  
Y = 1952800; 

% 3. Unproject to latitude and longitude (in degrees) 
[lat, lon] = projinv(p5179, X, Y);  

% 4. Display results 
fprintf('Latitude: %.6f°\nLongitude: %.6f°\n', lat, lon); 

For more clarifications refer to following documentation links:

1. Projcrs : https://www.mathworks.com/help/map/ref/projcrs.html
2. Projfwd: https://www.mathworks.com/help/map/ref/projcrs.projfwd.html

For version specific MATLAB documentation links type following commands in MATLAB command window:

web(fullfile(docroot, '/map/ref/projcrs.html')) 
web(fullfile(docroot, '/map/ref/projcrs.projfwd.html'))  

In case of any minute discrepancies between the obtained results and actual result refer to the following MATLAB answer link to understand why it is so:

https://www.mathworks.com/matlabcentral/answers/2173347-discrepancy-in-epsg-3003-coordinate-conversion-results-in-matlab#answer_1564578

Hope this helps you!