Creating a bathymetric map in QGIS 3.34 using GRASS v.surf.idw

Question

I am brand new to QGIS and GIS in general. I am attempting to create a bathymetric map using data I collected myself. I am trying to use this tutorial: https://www.youtube.com/watch?v=dGDr3BrmmNw

The steps I have followed are:

1. import csv data as a delimitted text layer (my csv file has latitude, longitude, and depth columns)
2. draw polygon boundary around the points on another layer
3. use GRASS v.surf.idw to create the raster
   • use the delimitted text vector layer as the input
   • use defaults for other inputs
   • select depth as the attribute value to interpret
   • run

However, when using the v.surf.idw processing tool, the output is not what is expected. The output raster only has a single band (and the minimum and maximum values are the same number which is 1.033). Essentially there is no raster at all showing up but I cannot figure out where I am going wrong.

My full project files are located here: https://github.com/stonepreston/rio_vista_qgis

Can someone take a look and see if I am going way wrong somewhere? It seems simple to do, but I cannot for the life of me get it working.

Answer 1

Set your Advanced parameters -> GRASS GIS region cellsize to > 0. As your data are in decimal degrees, use a rough conversion to meters. Something like 0.000002 (~20cm) should do given your extent and point spacing.

You can then clip to your extent: