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I need to generate a raster looking like a « heatmap » based on a points layer. On this layer, each point represents a nest (bird population study). I need to produce a nest density map (raster) from this layer. I noticed that rasters produced from Heatmaps and Interpolation plugins were somewhat similar, so I'm wondering if there is one plugin specifically recommended for what I need to achieve.

I specifically would like a square-shaped extent (with X,Y mini and X,Y maxi), that Heatmaps plugin does not do (Interpolation does). I would like this extent to be colored for zero values. One more thing: I don't have any attribute to be taken into account in my nests layer (Interpolation plugin asks for such an attribute to rely upon).

Then, I don't really get the difference between the two plugins.

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3  
A heat map is surface of observed density. Interpolation takes a variable that varies over space, and tries to use observations to determine an estimate of a variable where observations do not exist. While the output may often look similar, these are very different ideas. – Richard Law Mar 18 at 7:33
up vote 7 down vote accepted

Heatmaps and interpolations are completely different things though they might look similar. A heatmap visualizes "hotspots" in the distribution of features on the map i.e. dense areas will be highlighted in a heatmap, based on the parameters you use for processing it.

However the purpose of an interpolation is to estimate feature values at locations where no measurement data is available. If you would for example take a lot of temperature measurements in the field you can obviously not measure the temperature at every single location across the study area (i.e. you can't measure a continuous field). You would use the interpolation to estimate the temperature values between the measurement points.

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Thanks a lot! This is clearer... The Interpolation plugin seems to be closer to what I want to achieve, then... As I don't have any specific attribute to use as a variable, would it be acceptable to add a new attribute column filled with only 1 values (as each point is equivalent to 1 nest)? – wiltomap Mar 18 at 7:40
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I think the heatmap is what you need if you want to plot nest densities. Assuming you would do what you suggested and add a new attribute where the value for every nest is 1 the interpolation would return a monochrome rectangle. It would consider this specific attribute as being given at the nest locations. It would then try to estimate the attribute for all single locations between the nests. Since every nest has a value of 1 the interpolation would also return 1 for every other location. – TobsenB Mar 18 at 7:45
    
Basically a heatmap visualizes densities based on the point locations whereas the interpolation calculates an attribute value for a specific location based on the attribute values of measurements taken at other locations. If you want to plot the density of the nests a heatmap would be the right choice – TobsenB Mar 18 at 7:48
    
OK thanks a lot for your advice! I assume that it is not possible to get a coloured background with Heatmaps plugin (I only get circles around points that depends on radius value). – wiltomap Mar 18 at 8:14
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QGIS already comes along with heatmap visualization so you don't necessarily need a third party plugin. Just open your layer properties and go to the style tab. In the dropdown menu you can select heatmap I think that should get you what you try to achieve. – TobsenB Mar 18 at 8:18

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