Please help, Wrong Projection??

BadWolf · ‎03-25-2016

Dear all,

First of all I am new to ArcGis

I was given a shapefile with the information of the bathymetry of a Portuguese river reach. In the same shapefile "package" there was one file with the information of the projection, a *.prj file.

I have loaded the shapefile on ArcGis and I got this information:

Projected Coordinate System: Lisbon_Lisbon_Portuguese_Grid
Projection: Transverse_Mercator
false_easting: 0,00000000
false_northing: 0,00000000
central_meridian: 1,00000000
scale_factor: 1,00000000
latitude_of_origin: 39,66666667
Linear Unit: Meter
Geographic Coordinate System: GCS_Lisbon (Lisbon)
Datum: D_Lisbon
Prime Meridian: Lisbon
Angular Unit: Degree

This should be correct, but I used "layer to KML" and checked the location of this river in Google Earth, and it was placed on the sea, near Ibiza island. And this is a Portuguese river reach...

So, something is not correct here and I really do not know what can I do to project this river in the correct place... Can someone help me?

I know exactly the location of the river reach on Google Earth!

Thanks!

BadWolf · ‎03-27-2016

Dear Dan,

Sorry for the late reply. I have to thank you for your help! You were right! Projecting first to a geographic coordinate system solves all my problems!!!

THANK YOU SO MUCH!!!

pokkiri

This is a classic case where the .prj file exists but may have incorrect CRS information, or there's a datum/transformation issue between the Portuguese Grid and WGS84.

Before spending time on trial-and-error reprojection, it helps to verify what CRS the data is actually in by previewing it on a map. There's a free tool at projectionfinder.com that analyzes coordinate patterns and shows your data on a basemap - if it appears in the wrong location (like near Ibiza instead of Portugal), you immediately know the defined CRS is incorrect.

For Portuguese data specifically, common issues include confusion between the old Lisbon datum and newer ETRS89-based systems. The visual verification approach can save a lot of debugging time.