This is my first post here and I'm new to GIS and I'm not massively even sure what I'm asking, so please be gentle!

I'm attempting to learn QGIS through self-study and my idea is to take on a few different types of projects and puzzle my way through to learn that way. One of these is to make a map of my friend's farm... it's a small piece of land so I'll be working at a super zoomed-in level.

I've figured out how to get DEM data and make contour lines from that, but I've only been able to find data for 7.5 arc-seconds which isn't precise enough. I've done a bit of research and see that 1/3 arc-seconds exists and I'm wondering if this data will help me get more precise contour lines to be able to add them to the farm map?

Could someone please let me know where to find 1/3 arc-second DEM data for Portugal? Or if I'm completely off track on what I should be doing to achieve the contour lines, I'd be very happy to be pointed in the right direction!

  • you can try with SRTM which is a 1 second DEM (create an account here : urs.earthdata.nasa.gov and then use this website : dwtkns.com/srtm30m to download) but I doubt it will be enough at the scale of a farm. At this scale you probably need a DEM created from a drone. – Léo M May 25 '20 at 13:40

You can check the Copernicus EU-DEM, which has an estimated resolution of 1 second-arc (around 30m).

You can also find some elevation data for Portugal listed on this page. There is a 2m resolution DEM for some coastal regions, and 50m only for the rest of the country. I hope your area of interest is in a coastal area...!

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