# Pixel sizes, cartographic scales and maps

In spite of being a widely discussed topic, I have not been able to find the complete answer to my concerns regarding scale's use in maps preparation. I am interested in finding in the relationship(s) between pixel size and the best scale which can be derived from a particular product (image). Let's suppose I want to prepare a Land cover map (using unsupervised classification for example), using for that purpose only Landsat imagery (fixed 30x30m pixels), which criteria should be considered to define the 'best' achievable scale for the land cover map in this case?

• Could you add a few links to previous discussions? Aug 19, 2016 at 18:00

This is very simple. All you have to do is apply the Waldo Tobler, renowned analytical cartographer (now emeritus from University of California-Santa Barbara) rule:

“The rule is: divide the denominator of the map scale by 1,000 to get the detectable size in meters. The resolution is one half of this amount.”

So the formula is:

``````Raster resolution (in meters) = Map Scale / 1000 /2
``````

The formula above is to get the raster resolution, or its pixel size.

Hence, in order to discover the contrary, that is, what would be the map scale based on a pixels size of raster, you can apply the formula below:

``````Map Scale = Raster resolution (in meters) * 2 * 1000
``````

It means that a regular Landsat TM, ETM+ and OLI image with its 30 metres spatial resolution would be good enough to produce a 1:60000 scale map.