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tilezen / joerd

Joerd can be used to download, merge and generate tiles from digital elevation data
MIT License
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Canada: SRTM looking better than CDEM #189

Open daniloide opened 4 years ago

daniloide commented 4 years ago

Hi, First of all, thanks for the products you provide, they are awesome! I have a question regarding the Terrain Tiles.

I am working with some mapping for Canada and I find that a lot of the tiles height values are in about 1 meters intervals.

Here is an example: elevation-tiles-prod.s3.amazonaws.com/geotiff/14/3074/5309.tif

The original data source is CDEM, with a resolution from 20 to 400 m, and according to their documentation: "The  unit  of  measure  for  storing  vertical  data  is  the  metre. In  general, elevations are  expressed  as integers . They are expressed as floating point when ever available", being that the reason of the 1 m intervals. The point is that CDEM data may be better than SRTM in some places but also worse in others (most of them from what I have been testing).

Is there some way to use the TerrainTiles without the CDEM? It could be even better if it could be used only where resolution is better than SRTM (about 20 m horizontal and floats in vertical instead of integer), but looks far more complicated.

Thanks in advanced for any suggestions or ideas!!

nvkelso commented 4 years ago

There's a coverage database that controls which sources are used to build which geographic tiles. You can toggle the values there to change the effective zoom levels for each.

NOTE: This would require a new tile build. If you find values you like locally in Marble Cutter, than we can update the main config for the next global build (no schedule yet, but likely end of 2020).

fionag11 commented 4 years ago

It seems even the Canadian govt is abandoning CDEM https://open.canada.ca/data/en/dataset/7f245e4d-76c2-4caa-951a-45d1d2051333 I believe it was based on interpolation of point elevations, not remote sensing like the other datasets.