topic Re: Please help, Wrong Projection?? in Data Management Questions

Please help, Wrong Projection??

BadWolf — Sat, 26 Mar 2016 03:40:51 GMT

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!

Re: Please help, Wrong Projection??

DanPatterson_Retired — Sat, 26 Mar 2016 08:18:50 GMT

You will have to project your data to a WGS 1984 Web Mercator (Auxiliary Sphere) coordinate system... for example

Not lining up with Google Earth even after changing the projection

Re: Please help, Wrong Projection??

NeilAyres — Sat, 26 Mar 2016 08:33:32 GMT

And use the appropriate datum transformation between the Lisbon datum and WGS84.

Re: Please help, Wrong Projection??

NeilAyres — Sat, 26 Mar 2016 08:42:57 GMT

But be careful.

Portugal seems to have a rather complex history regarding geodetic control.

Several different versions listed in the documentation and in the EPSG database.

Including the very confusingly named :

Lisbon_1890_Lisbon_To_Lisbon

Might be useful to do a bit of research here on exactly what you are dealing with.

Re: Please help, Wrong Projection??

BadWolf — Sat, 26 Mar 2016 14:05:03 GMT

I have to truly thank you both for trying to help me!

I have researched on the EPSG database and I think I am dealing with EPSG:20790.

I have tried to to that transformation between datums and I always get a error after ArcGis process the "Project" feature...

Maybe I am choosing the wrong type of transformation? I have already tried a lot of them...

I will post here the data that I am working, can someone have a look on it please? I'm really lost!

Thanks again!!

Re: Please help, Wrong Projection??

DanPatterson_Retired — Sat, 26 Mar 2016 15:19:57 GMT

You of course, used the Define Projection tool first if the file didn't have a defined coordinate system. Then you can proceed to the Project tool. If it had a defined projection... that you can confirm in the layer's properties, you can skip the Define step.

Re: Please help, Wrong Projection??

BadWolf — Sat, 26 Mar 2016 15:45:58 GMT

Dear Dan,

I did not used "Define Projection" tool. The data that was given to me already had the information regarding the coordinate system.

I'm trying to do use the "Project" tool to project this data in the WGS 84 like you have said. But I can't, I always get an error. I will screenshot what I am doing.

Here I select this Geographic Transformation (the only one in this list).

After press "OK" I get this error:

I really do not know how to solve this...

Thanks!

Re: Please help, Wrong Projection??

DanPatterson_Retired — Sat, 26 Mar 2016 16:04:10 GMT

a screen grab of the properties of the layer would be useful... just to confirm what the extent of the file is, its type and to see if the defined coordinate system matches. Also... never save a file to the root directory of drive...just not good practice in some environments

Re: Please help, Wrong Projection??

BadWolf — Sat, 26 Mar 2016 16:18:48 GMT

Dear Dan, here I attach a screen grab of the properties of the layer:

Regarding the file, I am just saving this on the root of the drive just for testing purposes! My work is on other folders that I do not want to "contaminate" with testing purposes

Thanks for the help!!

Re: Please help, Wrong Projection??

DanPatterson_Retired — Sat, 26 Mar 2016 16:22:16 GMT

see if you can project the file to a geographic coordinate system first (aka a GCS WGS 84 or something standard). It may be the projected to projected coordinate system that is the issue. So in summary, project to decimal degrees, then project from decimal degrees to that webbie projection

Re: Please help, Wrong Projection??

BadWolf — Mon, 28 Mar 2016 02:21:52 GMT

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!!!

Re: Please help, Wrong Projection??

pokkiri — Sun, 28 Dec 2025 18:12:49 GMT

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.