I have a remote sensing image with GCS WGS 1984 / EPSG: 4326.

I need to extract pixel values from this image which corresponds to specific point locations. For that purpose, I defined these locations by entering their latitude and longitude in degrees. (I am using QGIS, I added the remote sensing image by using "add raster layer" and I defined the point locations by uploading a .csv file through "add delimited text layer"). Afterwards by using "identify features" tool in QGIS, I could access the pixel values of these locations.

My first question is, is the workflow I did follow correct? I am new in the field, and I am not sure if I missed some steps.

My second question is, (I am a bit confused how I can ask this, so please let me know if I need to clarify more) since the image I use is not projected to 2D, will this workflow give accurate results for the pixel values of these point locations? Or I need to project it first before extracting the pixel values?

  • Welcome to GIS.SE. Please refrain from asking two question at once, since this makes answering them harder - or finding the right answer later on. Also: How is your image not in 2D? Do you have a holo-projector? – Erik Jul 31 '19 at 13:27
  • By 2D, I was referring to the image I was working on not having a projected coordinate system such as EPSG:32633 WGS 84 / UTM zone 33N. – user146783 Jul 31 '19 at 13:41
  • That would be of importance when it comes to area calculation, but not on the issue of value extraction. – Erik Jul 31 '19 at 13:54
  • As long as the image has a defined spatial reference system (and it does) QGIS will project it "on-the-fly" to the CRS of your map. It's not necessary to put it in a projected coordinate system. The method suggested by @Rhodri_22 should work. The Sample raster values tool should also work. In my experience QGIS's native tools work better (faster, less likely to crash) than the SAGA tools. – csk Jul 31 '19 at 21:59

Could you please be more specific in the type of data you are using? But from my understanding, you have inserted a Raster file into QGIS, and a .csv file of points with x and y coordinate values. You would then like to extract the raster value to those points?

If this is the case, in QGIS, you can use the "Add raster values to points" tool from "SAGA" processing toolbox (As seen below)

Add raster values to points

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