Image has gaps at low zooms (i.e. z0-3)

[fungjj92]

Hi! I am using the cog module of titiler and trying to display data from z0/1 all the way to z15.

Two questions --

1. Can you explain what the scale querystring param does and why are the values only 1-4?

2. When showing this 600m raster at z0-3 using scale=2, titiler made an image with gaps

Adjusting to scale=3 or scale=4 got rid of gaps z2-3, but there are still gaps at z1.

This is what the request url looks like
tiles/cog/tiles/WebMercatorQuad/6/22/32.webp?url=<tif_uri>&bidx=1&rescale=0%2C650.0&return_mask=true&scale=3

Can you explain what's happening under the hood and how we can get rid of the gaps? We want a clean and continuous raster image.

Thank you!

[vincentsarago]

Can you explain what the scale querystring param does and why are the values only 1-4?

the scale define the size of the tile

https://github.com/developmentseed/titiler/blob/main/src/titiler/core/titiler/core/factory.py#L905-L910
1: 256x256
2: 512x512
3: 1024x1024
4: 2048x2048

it's limited to 4 because it was the default of mapbox gl when we started this project

When showing this 600m raster at z0-3 using scale=2, titiler made an image with gaps

I'm not sure what's going on without having a minimal reproducible example. What I can say is that you shouldn't use the scale parameter except if you tell your map client that it will get bigger tiles