Dfs1

A dfs1 file contains node-based line series data. Dfs1 files do not contain enough metadata to determine their geographical position, but have a relative distance from the origo. A common use case for dfs1 files is boundary conditions in MIKE 21 that vary along the boundary. Note that the MIKE FM engine treats the values as equidistant along the boundary regardless of the dx specified in the file.

import mikeio

ds = mikeio.read("../data/tide1.dfs1")
ds
<mikeio.Dataset>
title: Predicted tide level
dims: (time:97, x:10)
time: 2019-01-01 00:00:00 - 2019-01-03 00:00:00 (97 records)
geometry: Grid1D (n=10, dx=0.06667)
items:
  0:  Level <Water Level> (meter)

Grid 1D

The spatial information is available in the geometry attribute (accessible from Dfs1, Dataset, and DataArray), which in the case of a dfs1 file is a Grid1D geometry.

ds.geometry
<mikeio.Grid1D>
x: [0, 0.06667, ..., 0.6] (nx=10, dx=0.06667)

Grid1D’s primary properties and methods are:

  • x
  • nx
  • dx
  • find_index()
  • isel()

See API specification for details.

Creating a dfs1 file

  1. Create a datetime index
  2. Create a data array with dimensions (time, x)

In this example the grid consist of two points (west and east), but the same approach can be used for any number of points.

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import mikeio

t = pd.date_range("2021-01-01", periods=100, freq="15min")
t_rel = (t - t[0]).total_seconds().values

west = np.sin(t_rel / 3600)
east = 1.2*np.sin(t_rel / 3600 + 0.5)

data = np.column_stack((west, east))
data.shape
(100, 2)
  1. Create a Grid1D geometry with the number of points in the x-direction and the spacing.
geometry = mikeio.Grid1D(nx=2, dx=1)
geometry
<mikeio.Grid1D>
x: [0, 1] (nx=2, dx=1)
  1. Create a DataArray object with the data, time, geometry, and item information.
da = mikeio.DataArray(
    data,
    time=t,
    geometry=geometry,
    item=mikeio.ItemInfo("Water level", mikeio.EUMType.Water_Level),
)
da
<mikeio.DataArray>
name: Water level
dims: (time:100, x:2)
time: 2021-01-01 00:00:00 - 2021-01-02 00:45:00 (100 records)
geometry: Grid1D (n=2, dx=1)
da.plot.timeseries()

Optional, repeat step 4 for additional items to create a Dataset.

  1. Write to a dfs1 file.
da.to_dfs("boundary.dfs1")