[Qgis-user] Fwd: Question

[Nicolas Cadieux]

Hi,

Ok what you want to do is to sample a raster with data points (and not 
merge two rasters).   This mean you have a csv of points and a raster 
with values.  You want the values of the raster to be added to a column 
in the csv.   When you open both layers, do they appear to be well 
placed in space (georeferenced) and one on top of the other?  If not, 
right click on the layer in the layer panel and go to "set CRS/Set layer 
CRS".  Once both layers are in the correct CRS, they should be one on 
top of the other.

Then used the Processing tool (sample raster values) or install the 
Point Sampling tool. Both are plugins that need to be activated under 
the plugins menu but the Point Sampling tool will need to be installed 
first.  You will need to save the CSV in another format because you 
cannot write to a CSV.  Use Shp or better, Geopackage.

Nicolas


On 2020-05-06 10:48 a.m., Nikos Benos wrote:
> Dear Nicolas,
>
> I have used the following methodology
> https://www.qgistutorials.com/en/docs/3/sampling_raster_data.html
> It works fine, but the problem is that the coordinates of the tiff 
> file are in different scale than the coordinates of the csv file.
> If I convert my csv file (list of points with their coordinates) in 
> raster file, how will I combine 2 raster files to produce an excel file?
> Thank you very much in advance for your help.
>
> Best,
> Nikos
>
> Στις Τετ, 6 Μαΐ 2020 στις 4:36 μ.μ., ο/η Nicolas Cadieux 
> <nicolas.cadieux at archeotec.ca <mailto:nicolas.cadieux at archeotec.ca>> 
> έγραψε:
>
>     Hi,
>
>     You can save a file and reproject it by changing the coordinates
>     reference system (CRS).  That would change the coordinates (and
>     the data dependent on the method used).  However, the is the csv a
>     vector file (a file with a list of points for example) or is it a
>     true raster file (a matrix).  If it’s a vector file, you will need
>     to change it as a raster.  Look for rasterize or « vector to
>     raster ».  Google it to understand the differences between raster
>     and vector.
>
>     Nicolas Cadieux
>     Ça va bien aller!
>
>>     Le 6 mai 2020 à 02:22, Nikos Benos <nbenos at uoi.gr
>>     <mailto:nbenos at uoi.gr>> a écrit :
>>
>>     
>>
>>
>>     ---------- Forwarded message ---------
>>     Από: *Nikos Benos* <nbenos at uoi.gr <mailto:nbenos at uoi.gr>>
>>     Date: Τρί, 5 Μαΐ 2020 στις 12:25 μ.μ.
>>     Subject: Question
>>     To: <qgis-user at lists.osgeo.org <mailto:qgis-user at lists.osgeo.org>>
>>
>>
>>     Dear Sir or Madam,
>>
>>     I hope all is well with you. I have converted a png file to a
>>     tiff file (when I attached it to the e-mail, the e-mail became
>>     too big and was not sent). I have been trying to combine the tiff
>>     file with a csv file with no success. The reason is that the
>>     coordinate units are different between the 2 files.
>>     Since I have constructed myself the csv file, is there any way to
>>     transform the coordinate units of the png file to make them
>>     compatible to those of the csv file?
>>     Thank you very much in advance for our help and I am sorry if
>>     this is a vdery simple question, but I am very new to QGIS.
>>
>>     Best regards,
>>     Nikos Benos
>>     -- 
>>     Dr Nikos Benos
>>     Associate Professor
>>     Department of Economics
>>     University of Ioannina
>>     University Campus
>>     45110 Ioannina
>>     GREECE
>>     Tel: +30-26510-05955
>>     Fax: +30-26510-05092
>>     e-mail:nbenos at uoi.gr  <mailto:nbenos at uoi.gr>
>>
>>
>>     -- 
>>     Dr Nikos Benos
>>     Associate Professor
>>     Department of Economics
>>     University of Ioannina
>>     University Campus
>>     45110 Ioannina
>>     GREECE
>>     Tel: +30-26510-05955
>>     Fax: +30-26510-05092
>>     e-mail:nbenos at uoi.gr  <mailto:nbenos at uoi.gr>
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>
>
> -- 
> Dr Nikos Benos
> Associate Professor
> Department of Economics
> University of Ioannina
> University Campus
> 45110 Ioannina
> GREECE
> Tel: +30-26510-05955
> Fax: +30-26510-05092
> e-mail:nbenos at uoi.gr  <mailto:nbenos at uoi.gr>
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