# Formulation of CRS (EPSG2438 to EPSG4326) conversion in Excel

I have about 14000 points with coordinates EPSG2438 and want to convert the coordinates into WGS84 (EPSG4326). I want to know that is there a way to make Excel formula to convert these coordinates. In QGIS (and I suppose in other GIS packages as well) when we want to change CRS, we can see certain information associated with each EPSG. For Example for EPSG4326

``````Extent: -180.00, -90.00, 180.00, 90.00
Proj4: +proj=longlat +datum=WGS84 +no_defs
``````

and for EPSG2438

``````Extent: 121.50, 28.22, 124.50, 53.56
Proj4: +proj=tmerc +lat_0=0 +lon_0=123 +k=1 +x_0=500000 +y_0=0 +ellps=krass
+towgs84=15.8,-154.4,-82.3,0,0,0,0 +units=m +no_defs
``````

Can this associated information be used to convert from EPSG2438 to EPSG4326 and vice versa?

• it would be easiest to use ogr2ogr on a csv file – Ian Turton Nov 26 '18 at 8:53
• This seems promising and more convenient. But I am confused by the complex syntex of this command line took. – datakeen Nov 26 '18 at 19:05
• Thank you all for giving a hand for help. I finally landed on Surfer 13 for the conversion. For the benefit of others who are not proficient with command line tool like ogr2ogr or through other complex methods, I am writing it here. Open your CSV or spreadsheet, containing coordinates data, using File|Open. Then go to Data|Coordinate System|New Projected Coordinates. Rest of things are straightforward. Just choose source X and Y columns, Target (empty) columns for converted X and Y. Also choose source source and target Coordinate Systems and press OK. – datakeen Nov 27 '18 at 15:33

QGIS uses a package called "PROJ4" to do the computation based on those coordinate reference specifications. The mathematics of transforming from X-Y coordinates to lat-long on an ellipsoid based on wrapping a cylinder round the Earth (which is what `+proj=tmerc` means, basically) are quite complicated.
But as mentioned in comments, saving as a CSV and using `ogr2ogr` or using QGIS might be easier.