use pyflwdir package to parse nextxy data of CaMa-Flood! about pyflwdir HOT 8 CLOSED

Yes -10 is inland termination, while -9 is for usual river mouth flowing to ocean,

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Hi @Jiangchao3,

Thanks for using pyflwdir!

I had a look at your data and noticed that pits have a value of -10 instead of -9 in the nextxy data. Perhaps this has changed in the recent CaMa-Flood updates? Pinging Prof Yamazaki (@bigasmountain) here to confirm this has indeed changed in which case I'll update the code.

For now you can just change the pit values in the nextxy data to use pyflwdir.

import pyflwdir
import rasterio
import numpy as np

# read data
with rasterio.open('nextxy.tif') as src:
    data = src.read()
    transform = src.transform
    latlon = src.crs.is_geographic

# change pit values and parse with pyflwdir
data = np.where(data==-10, -9, data)
flw = pyflwdir.from_array(data, ftype='nextxy')

To make nice visualization you will want to use either the vectorize or streams method. Both methods can take an additional xs and ys argument with the outlet x and y coordinates which will make your visualizations look much better.

Hope this helps! Dirk

PS. For a next issue anywhere on github it is always useful if you paste the actual code instead of a screenshot to quickly be able to reproduce it. Otherwise your issue was really clear and had the data for me to debug it!

Hi @DirkEilander , your recomended script worked after replace the pits of -10 with -9. I will spend some time to further learn the whole package of pyflwdir. And looking forward to your update of the code to be able to parse the new river network dataset of cama-flood. Many thanks for your kindly help.

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This is fixed in 16b1ac0 (still unrealeased - for now you get the update by updating pyflwdir directly from git)
In addition I've added a convenience method to read the binary CaMa-Flood nextxy data.
The following example should provide a nice plot of your CaMa-Flood rivers.

# %%
import pyflwdir

# %% read data
bbox=[-180, -90, 180, 90]
data, transform = pyflwdir.read_nextxy(
    fn='nextxy.bin', nrow=720, ncol=1440, bbox=bbox
)
flw = pyflwdir.from_array(
    data,
    ftype='nextxy',
    latlon=True,
    transform = transform

)
# %% vectorize streams
import geopandas as gpd
feats = flw.streams(strord=flw.stream_order(), min_sto=2)
gdf = gpd.GeoDataFrame.from_features(feats, crs=4326)

# %% drop lines crossing anti-meridian
import numpy as np
def check_crossing(line):
    return np.any(np.abs(np.diff([xy[0] for xy in line.coords[:]]))>180)
drop_lines = np.vectorize(check_crossing)(gdf.geometry)
gdf1 = gdf[~drop_lines]

#%% plot values by stream order
gdf1.sort_values('strord').plot(column='strord')

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Hi @DirkEilander, the above script you provided works well, many thanks to your sincere help!

from pyflwdir.

And I also email to Prof. Dai Yamazaki, he replied that the traditionary GMT and Fortran code for river network visualization don't work now, so I am trying to learn the pyflwdir toolbox recently.

from pyflwdir.

Hi @Jiangchao3,

Thanks for using pyflwdir!

I had a look at your data and noticed that pits have a value of -10 instead of -9 in the nextxy data. Perhaps this has changed in the recent CaMa-Flood updates? Pinging Prof Yamazaki (@bigasmountain) here to confirm this has indeed changed in which case I'll update the code.

For now you can just change the pit values in the nextxy data to use pyflwdir.

import pyflwdir
import rasterio
import numpy as np

# read data
with rasterio.open('nextxy.tif') as src:
    data = src.read()
    transform = src.transform
    latlon = src.crs.is_geographic

# change pit values and parse with pyflwdir
data = np.where(data==-10, -9, data)
flw = pyflwdir.from_array(data, ftype='nextxy')

To make nice visualization you will want to use either the vectorize or streams method. Both methods can take an additional xs and ys argument with the outlet x and y coordinates which will make your visualizations look much better.

Hope this helps!
Dirk

PS. For a next issue anywhere on github it is always useful if you paste the actual code instead of a screenshot to quickly be able to reproduce it. Otherwise your issue was really clear and had the data for me to debug it!

from pyflwdir.

Hi @DirkEilander and @bigasmountain, thanks very much for your kindly reply.
I will follow your suggestions to paste the code instead of screenshot on any of my next github issue.

And yes I also noticed that the latest CaMa-Flood manual describes that -10 represents the inland termination while -9 represents the river mouth.

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So great for providing such a detailed script. I will check it after getting back to office tomorrow! Thanks again!

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