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I am getting started with QGIS and have some confusion about base maps and their data.

For example, say I start with the ESRI National Geographic USA Topo Maps as my base map (a new tile layer, using the URL provided by QMS Search). I can render it as contours, but there is no labels information in the layer properties so I cannot label the actual elevation.

If I export my map as TIFF or Geo PDF, then I can add the labels. But, the elevations seem inverted (higher elevations have lower numbers).

And, related, I would like to turn off all data in the base map except elevation (removing roads, counties, etc.)

I seem to be missing something about how to access the use the actual data (in my case, the elevation data) underlying a base map. Can you point me in the right direction?

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  • Ah. Now I get it. Thank you for clarifying!
    – erikor
    Commented Aug 15 at 1:35
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    @user2856 that comment would make a good answer to this question
    – Ian Turton
    Commented Aug 15 at 8:19

2 Answers 2

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Your basemap is a pre-rendered map image. It's not a set of data layers you can use individually.

If you just want to display contours, you'll need to find a contour vector dataset (feature class e.g. shapefile/gdb/geopackage or a feature service).

One for the US is from NationalMap - https://carto.nationalmap.gov/arcgis/rest/services/contours/MapServer

Add conn

Conn prop

Data

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  • Now I get it. Als I didn't realize there were contour vector datasets available. The QGis learning curve is a hair steep but wow is that a powerful collection of tools and resources.
    – erikor
    Commented Aug 15 at 13:42
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What you can do based on pre-installed tools in QGIS:

  1. Load a DEM, a Digital Elevation Model: a data layer representing elevation. In XYZ-tiles, you have pre-installed a link to Mapzen Global terrain for worldwide elevations. Drag-and-drop this to the Layers panel to load the DEM as a raster layer (or use any other DEM).

  2. Change the rendering style to Contours. You can then style two different types: Countour interval (like every 100 meters) and Index Contour Interval (like every 500 m). See screenshot 1 below.

  3. To label these lines, you must extract the contours from the DEM. Save the extent of the DEM for your region of interest to a local drive (right click layer -> Export). Then use Menu Raster -> Extraction -> Contour. The resulting layer can then be labeled based on the ELEV attribute. See screenshot 2.

Screenshot 1: DEM rendered as contours:

enter image description here

Screenshot 2: Extracted contours with labels based on ELEV:

enter image description here

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    Nice. This also clarifies another problem I was having...I was getting errors trying to extract contours from internet service based layers due to the files being "missing". Saving the relevant region of interest locally as you mention solves that. Thanks!
    – erikor
    Commented Aug 15 at 13:41

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