[Qgis-user] On-the-Fly Projections Versus Manual Re-projections

[Nicolas Cadieux]

Hi,

These are two very different projections. I would load a base map from 
Quickmap services plugin to see if files are being loaded correctly.  If 
the files are in 4326, and are loaded in 4326, then all is good if they 
are well georeferenced (use the Quickmap base map to make sure).  If 
files don't have a CRS, they may been incorrectly loaded if you have the 
"use project CRS" or "Use a default CRS" in the options/CRS/CRS for new 
layers menu.

If a file is in 4326 but incorrectly loaded in another projection, you 
need to correct the CRS not reproject it with GDAL WARP.    Simply right 
click on the layer in the layers panel, change the CRS (Set CRS/set 
layer CRS) (Qgis 3x) and save the file under a new name.  That should 
change the CRS and the file position on the map.  If you are still in 
the wrong place, you need to make some guess work.

Nicolas


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


Extent: 123.73, 4.76, 126.65, 21.97 Proj4: +proj=tmerc +lat_0=0 
+lon_0=125 +k=0.99995 +x_0=500000 +y_0=0 +ellps=clrk66 
+towgs84=-127.62,-67.24,-47.04,-3.068,4.903,1.578,-1.06 +units=m +no_defs


On 2018-11-01 1:02 PM, Aj Hollenbach wrote:
> Hi QGIS Community,
>
> I have what I believe may be a fairly straight-forward question on 
> coordinate reference systems and projections in QGIS. I am currently 
> working on some maps in the southern Philippines and thus have set my 
> "project-level" coordinate reference system (CRS) to EPSG 3125. I have 
> noticed, however, that when I open a vector file or raster file that 
> is loaded into this project, the CRS still reads as EPSG 4326. Thus, 
> my question is whether it is necessary to "manually" go in and change 
> the EPSG of each new layer to EPSG 3125 (i.e. use the Warp Tool for a 
> raster file or the "Reproject Layer" tool for a vector file), or if 
> there is any issue with leaving them as EPSG 4326. I note that I am 
> not having any issues "seeing" the newly added files--meaning the 
> "on-the-fly" projection seems to be working fine. Appreciate any 
> insights that you might have.
>
> Regards,
> Allen
>
>
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