Estimated rendering time

Estimated rendering time is a feature introduced in MapTiler Engine 11.2.
In this article, you’ll learn more about the meaning of this and other estimated parameters.

Due to technical aspects, the displayed values are just a rough estimate of the expected output parameters. In most cases, they will overshoot the real values, but it is important to note that they are supposed to give you a general idea of the rendering settings’ impact on the output.

Output settings page

One of the steps you need to take during the rendering process is setting the parameters of the output tiles. The page looks like this:

It is divided into 3 sections:

• Output tile format - lets you set the file format in which the generated tiles will be stored as well as the image compression parameters. Also, there is a switch that lets you choose if the output should include transparency data.
• Zoom levels - here you can set the minimum and maximum zoom levels of the rendered map. Also, using the checkbox on the right-hand side of the window, you can set the tiles to be generated in the HiDPI / Retina format.
• Estimates - this section contains the pre-rendering estimates based on the chosen rendering parameters.

Estimated rendering time and output size

These parameters are influenced by several factors:

• Format of the output tiles - different file formats implement different algorithms and store the data differently, resulting in the output file size being different. Moreover, due to implementation differences, some are faster than others which impacts the rendering speed.
• Max zoom - the maximum zoom level impacts the number of tiles being generated. The higher is the zoom level, the more tiles the output file will contain thus its size will increase and it will take more time to finish the rendering process.
• HiDPI / Retina tiles - choosing this option increases the tile size from 256x256 to 512x512, increasing the output size approximately 4 times. If you don’t set the zoom levels explicitly, after choosing HiDPI / Retina tiles, MapTiler Engine will modify them so that the output size stays more or less the same.

Estimated output data resolution at max zoom

The smallest element of the output map is the pixel of a tile at the maximal zoom level which accounts for a certain piece of the area represented by the generated map. Resolution at max zoom tells you how many meters in the real world the said pixel represents (in both X and Y axes). In a way, you can compare it to a classic map scale. This parameter is influenced by two main factors:

• Max zoom - the bigger is the zoom level, the more tiles the input image will be cut into. The tiles have a fixed size, and with increasing zoom levels they account for a smaller area of the output map, so effectively a pixel of a tile at maximal zoom level will represent a smaller area in the real world. The resolution will increase (the displayed value will be smaller).
• HiDPI / Retina tiles - as HiDPI / Retina tiles are twice as big in both dimensions than the standard ones, choosing this option while leaving the max zoom level unchanged will increase the resolution by a factor of 2 (the displayed value will be halved).

Resolution at the latitude of your data

The Mercator projection is probably the most commonly used projection in modern online maps. It has several advantages, but one of its downsides is that the distance represented in this projection varies with latitude. With the increase in latitude, the same distance on a map accounts for a smaller distance in the real world. Hence the areas closer to the poles are disproportionally big. Due to this fact, the value of the resolution explained in the previous paragraph, is correct basically only at the Equator. This article explains the problem pretty well.

The resolution estimate displayed in MapTiler Engine includes also a value that accounts for the effect of the Mercator projection and shows you the real resolution your output map will have at the maximal zoom level.

Conclusion

In this article, we have presented the pre-rendering estimates feature. You should now have a better idea, of what the estimated parameters mean and how the output settings impact the rendering process as well as the generated map package.

Useful links

Tiles à la Google Maps - Coordinates, Tile Bounds, and Projection
Understanding scale and resolution
Map scale