3 ms·

That's a nice experiment, take something a mundane as contour lines, turn it to eleven and see where it gets you. Is it a materialized remapping of the underly

by usrusr 5y ago

That's a nice experiment, take something a mundane as contour lines, turn it to eleven and see where it gets you. Is it a materialized remapping of the underlying .hgt or is it done client-side, in some webGL-shader? (if we'd even need that, plain js or wasm might be good enough these days?) I could imagine this being even more compelling if we could interactively shift the remapping to put regions we are currently interested in into high saturation parts (and/or scaling it down to make mountain ranges "readable"). Another, even simpler reading help would be sampling the color at the mouse position and displaying a translation into meters. In any case, the vertical perception amplification (compared to other visualisations) is truly awesome! in my region I can easily make out the forest offsets that SRTM and LIDAR data happens to come with, and bigger roads cutting through those forests.

jamessb 5y ago
> Is it a materialized remapping of the underlying .hgt or is it done client-side, in some webGL-shader? The map loads pre-rendered map tiles as JPG images from Amazon S3 (you can confirm this in the Network tab of your browser's dev tools). The page says: > This map layer is hosted as a public service, and map tiles are free to use under a Creative Commons 4.0 Attribution-NonCommercial-ShareAlike license.
- jimmySixDOF 5y ago
  Geosynced DEMs prepped to feed into microwave link design software can cost a lot of money. I knew one engineer who was sent up in a special plane they found just to photograph a remote region and then he matched the elevation data by hand for all the routes. I don't know what the non commercial uses are for this data but I suspect it would be otherwise prohibitively expensive without the CC4.0 license so I am happy for whomever it benefits.
zhdc1 5y ago
It looks like he's using vanilla Leaflet and a tile map. Gdaltile My guess is that he used GDAL to color and tile the DEM. GDAL can work with hgt files, but the DEM he used probably came as a bunch of geotiffs (I haven't checked, but that's pretty standard practice iirc). > Another, even simpler reading help would be sampling the color at the mouse position and displaying a translation into meters. If he's using gdal2tiles to create the tile map, he's likely converting the DEM to an 8 bit raster somewhere in the process, so the information conveyed by each of tiles will be less than ideal. There are ways around this, but they would take some effort, which may be more than what the author wanted to put in.
mrgriscom 5y ago
I used the typical GDAL tools -- gdalwarp, gdaldem, with some associated scripts of my own. I recall not using GDAL's image pyramid builder as I ran into some issues with wrapping at the int'l date line and in general wanted more fine-grained control over the process. This could be rendered dynamically using the elevation tile services now available from mapbox, et al. I wanted to use Jon de Ferranti's dataset specifically though due to his commitment to uniform global quality. An additional issue is since the color ramp is quite jagged, aliasing would be quite unsightly when zoomed out. You'd need a hefty amount of supersampling to get back the desired smoothness... not sure the tile services can support that easily.

by usrusr 5y ago

jamessb 5y ago

> Is it a materialized remapping of the underlying .hgt or is it done client-side, in some webGL-shader? The map loads pre-rendered map tiles as JPG images from Amazon S3 (you can confirm this in the Network tab of your browser's dev tools). The page says: > This map layer is hosted as a public service, and map tiles are free to use under a Creative Commons 4.0 Attribution-NonCommercial-ShareAlike license.

jimmySixDOF 5y ago
Geosynced DEMs prepped to feed into microwave link design software can cost a lot of money. I knew one engineer who was sent up in a special plane they found just to photograph a remote region and then he matched the elevation data by hand for all the routes. I don't know what the non commercial uses are for this data but I suspect it would be otherwise prohibitively expensive without the CC4.0 license so I am happy for whomever it benefits.

zhdc1 5y ago

It looks like he's using vanilla Leaflet and a tile map. Gdaltile My guess is that he used GDAL to color and tile the DEM. GDAL can work with hgt files, but the DEM he used probably came as a bunch of geotiffs (I haven't checked, but that's pretty standard practice iirc). > Another, even simpler reading help would be sampling the color at the mouse position and displaying a translation into meters. If he's using gdal2tiles to create the tile map, he's likely converting the DEM to an 8 bit raster somewhere in the process, so the information conveyed by each of tiles will be less than ideal. There are ways around this, but they would take some effort, which may be more than what the author wanted to put in.

mrgriscom 5y ago

I used the typical GDAL tools -- gdalwarp, gdaldem, with some associated scripts of my own. I recall not using GDAL's image pyramid builder as I ran into some issues with wrapping at the int'l date line and in general wanted more fine-grained control over the process. This could be rendered dynamically using the elevation tile services now available from mapbox, et al. I wanted to use Jon de Ferranti's dataset specifically though due to his commitment to uniform global quality. An additional issue is since the color ramp is quite jagged, aliasing would be quite unsightly when zoomed out. You'd need a hefty amount of supersampling to get back the desired smoothness... not sure the tile services can support that easily.