2

I am completely new to GIS, am currently using QGIS to try and accomplish a major feat.

Background: I have a file of over 150,000 property lat/long coordinates that exist in WA & OR (USA). I have also downloaded the data behind this map, the metadata and GeoTIFF files for WA and OR can be found here.

Data:

  1. Assume my list of coordinates is a CSV file with three columns: a unique property ID, a latitude and a longitude.
  2. I've loaded the GeoTIFF files for OR and WA from the above links into QGIS and replicated the ESRI link also above. Note that there are 10 color classes that correspond to the probability of a burn occurring in a given area; where the lightest red has a likelihood somewhere between a 0 to 1-in-10,000 chance, and the deepest red has a likelihood somewhere between a 1-in-22 to 1-in-8 chance.

Problem: For each row in my CSV file, I'd like to assign the burn probability value it would, should it be mapped on the map in QGIS. Note, I know how to map these coordinates; that is not what I'm seeking to accomplish. I'd like my CSV to have a new, fourth, column: the burn probability at this given location:

PropertyID Latitude Longitude BP_at_coor
input input input output

I want a table like this, for all coordinates provided.

Constraints: I do not have access to any other mapping software besides QGIS. I have access to SQL and Python. I am still learning how raster files work, and do not understand how to scrape them using Python; nor am I aware of any functionality in QGIS that will obtain the score from the raster and compute it for the coordinate in a way that produces what I'm seeking.

Additional Resources I found additional metadata for the map, here and noticed a hyperlink at the bottom that reads "Compute Pixel Location" which seems promising, but I have no idea how this works.

3
  • 1
    What have you tried so far?
    – Ian Turton
    Apr 21, 2022 at 18:39
  • See this answer which uses the raster_value() function of the field calculator.
    – Matt
    Apr 21, 2022 at 20:07
  • What I have tried so far is A LOT of googling / searching, but not really finding anything that fits my exact use case. I've also tried playing around with QGIS (I've been a user for 3 days). I have access to python but I'm also a newbie there, my experience is more data science. Geospatial analysis is a whole new world for me right now.
    – brisamh
    Apr 21, 2022 at 20:42

1 Answer 1

2

You can use the Point Sampling Tool plugin to extract the burn probability values to your existing property points.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.