[gdal-dev] gdal2tiles with GeoTIFF which crosses antimeridian?

[James Russo]

Good Evening,

I'm just following up on this question from a few days ago with some more
information and the script I am using which reproduces this issue.

The example results can be found here at the s3 links below and are all
generated from the same original GeoTIFF. The only difference is that on
one of them I slice off all data left of the 180, the other one the map is
left complete. The html files are set to the same example point and zoom
level to show how that without slicing the file, the image quality is very
poor. The one thing I notice is that if I include the 180 meridian, the
number of tiles generated is far larger (46k vs 8k).

Bad Results:

http://halo3.net/alaska_tiles_no_slice/leaflet.html

Good Results:

http://halo3.net/alaska_tiles_sliced_at_180/leaflet.html


Below is the script I use to generate both tile sets. It will automatically
download, unzip and process the input file I am using producing the same
results shown at the links above.

I'd appreciate any insight into the issue and how I might be able to get it
resolved? I'm still quite a novice at all this GIS stuff, but it has been a
fun experience so far.

Thanks,

-jr


---snip---
#!/bin/bash

wget -SN https://aeronav.faa.gov/content/aeronav/Planning/AK_WallPlan_2.zip
&& unzip -xo AK_WallPlan_2.zip
mv "Alaska Wall Planning Chart 2.tif" Alaska_Wall_Planning_Chart_2.tif
gdal_translate  -expand rgb  -strict  -co TILED=YES -co COMPRESS=LZW  -co
BIGTIFF=YES Alaska_Wall_Planning_Chart_2.tif alaska_expanded_rgb.vrt
gdalwarp -t_srs EPSG:3857 -r lanczos -overwrite -multi -wo
NUM_THREADS=ALL_CPUS -wm 1024 --config GDAL_CACHEMAX 1024 -co TILED=YES
alaska_expanded_rgb.vrt alaska_warped.vrt
gdalwarp -t_srs EPSG:3857 -te -19979999 6016546 -13438444 11497579 -r
lanczos -overwrite -multi -wo NUM_THREADS=ALL_CPUS -wm 1024 --config
GDAL_CACHEMAX 1024 -co TILED=YES alaska_expanded_rgb.vrt alaska_warped.vrt
rm -rf alaska_tiles_no_slice
rm -rf alaska_tiles_sliced_at_180
gdalinfo alaska_warped.vrt
time gdal2tiles.py -vvv -z 0-9 --processes=16 -r lanczos -w leaflet
alaska_warped.vrt alaska_tiles_no_slice
gdalinfo alaska_warped_sliced_at_180.vrt
time gdal2tiles.py -vvv -z 0-9 --processes=16 -r lanczos -w leaflet
alaska_warped_sliced_at_180.vrt alaska_tiles_sliced_at_180

---snip---









On Tue, Nov 24, 2020 at 6:20 AM James Russo <jr at halo3.net> wrote:

> Good Evening,
>
> GIS novice here. I have a GEOTiff that I'm trying to create tiles from
> which crosses the 180. It's a FAA sectional chart from the US used for
> aviation. If I slice off anything west of the 180, I can generate the tiles
> and they look good. If I don't the area of the tiles is super large and the
> resulting tile set is very pixelated.
>
> The source file is located here in zip form (
> https://aeronav.faa.gov/content/aeronav/Planning/AK_WallPlan_2.zip)
>
> I've tried some of the solutions that specify to use the CONFIG_LONG
> option, but that doesn't seem to be impacting anything. The only solution I
> have come up with is to cut off the area which crosses the 180 which yields
> good results.
>
> I've included below the commands I've been using.  I'm looking for any
> suggestions/guidance. I realize this is somewhat of a common problem. Even
> MapTiler had the problem, but they have sent an updated version which
> supposedly fixes it, but I can't afford that solution at this point so I'd
> like to stick to GDAL if possible.
>
> Thanks,
>
> -jr
>
>
> --- snip --
>
> gdal_translate \
>     -expand rgb \
>     -strict \
>     -co TILED=YES \
>     -co COMPRESS=LZW \
>     -co BIGTIFF=YES \
>     alaska.tif alaska_expanded_rgb.vrt
>
> gdalwarp \
>        -overwrite                  \
>        -cutline "Alaska_Wall_Planning_Chart.shp"       \
>        -crop_to_cutline            \
>        -cblend 10                  \
>        -r lanczos                  \
>        -dstalpha                   \
>        -co ALPHA=YES               \
>        -co TILED=YES               \
>        -multi                      \
>        -wo NUM_THREADS=ALL_CPUS    \
>        -wm 1024                    \
>        --config GDAL_CACHEMAX 1024 \
>        "alaska_expanded_rgb.vrt"   \
>        "alaska_clipped.vrt"
>
> gdalwarp \
>         -t_srs EPSG:3857            \
>         -te -19497422 6016546 -13438444 11497579 \
>         -r lanczos                  \
>         -overwrite                  \
>         -multi                      \
>         -wo NUM_THREADS=ALL_CPUS    \
>         -wm 1024                    \
>         --config GDAL_CACHEMAX 1024 \
>         -co TILED=YES               \
>         "alaska_clipped.vrt" \
>         "alaska_warped.vrt"
>
> gdal2tiles.py -z 0-8 --processes=16 -r lanczos -w leaflet alaska_warped.vrt
>
>
>
>
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