Choosing a Zoom Level for Downloaded Maps

Zoom Level: Background Information

When you download a map for offline use, Gaia GPS will ask you to select a zoom level.

On Android, there's a slider like this:

On iOS, there are three options - Low, Medium, and High.

• High corresponds to the maximum zoom level for the source.
  
  • Note: The maximum zoom for Gaia Topo and Gaia Streets is 12 because it is a vector source. Read on to learn more.
    
• Medium is 15
• Low is 13

The max zoom, also known as "zoom level", you choose represents the level of detail you want to download for that area. The same map layer downloaded with a zoom level of 18 will have more detail than a map downloaded with a zoom level of 15. 

Users familiar with topo maps may be thinking that this sounds similar to numeric map scale, and they would be correct. Numeric map scale refers to the relationship (or ratio) between distance on a map and the distance on the ground.

For example, on a 1:24,000 scale map, 1 inch on the map is 24,000 inches, or 2000 feet, on the ground. Print maps are often referred to by their scale in this way.

Zoom level is the digital equivalent of numeric map scale.

Why use "zoom level" and not "scale" in the app? 

Calculating the numeric map scale for a digital display is complicated because it involves the screen size and resolution, which can be different for every device.   

Furthermore, digital maps can be either raster or vector, which have different display properties.

Raster maps are constructed of a grid of images, with different images for different zoom levels.  Most of the maps in Gaia GPS are raster maps. This is why when you zoom all the way in on some map sources, the labels become large and fuzzy.

For example, USGS Topo is a raster map:

Vector maps are composed of points and lines. Vector maps are "lossless". As you zoom in, it does not get blurry. Instead, the different components of the map, like contour lines, hillshading, or labels all resize using independent scales. This allows you to zoom really far in on an area while retaining clear topo lines, labels, and POI icons.

Compare USGS Topo above to the recently updated Gaia Topo below. Both are of Logan Pass and both are from the same zoom level.

Notice how much more information can be viewed in the Gaia Topo vector map. There's space for more detailed trails, parking lot, bathroom, and trailhead POIs, all with perfect clarity. Where raster maps are limited by how much they can legibly print in a small space, vector maps are not.

• Interested in more map info? See: How Do Maps Work in Gaia GPS?

Scale for Raster and Vector Maps

Because Gaia GPS is used on many different devices with many different screen sizes, and given the complexity of map scale calculations using multiple map types, an exact scale for a downloaded area can't be easily calculated.

This means the scale displayed for map downloads is an estimate.

Raster Map Zoom Level

The table below is an approximate reference for how the zoom level corresponds to the numeric map scale for a raster map.  We recommend experimenting to see what zoom level works best for you, but we find that a zoom level of 14 or 15 is adequate for most outdoor activities.

Vector Map Zoom Level

As mentioned above, vector map scale is significantly more complicated. 

But to give a very rough estimate for sources based on Gaia Topo (Gaia Topo (feet and meters), Gaia Streets), the maximum zoom of 12 approximately corresponds to a 1:8,000 scale.