SimpleGridDB

The SimpleGridDB is very similar to the SimpleDB but the values must be provided at locations on a logically rectangular grid aligned with the coordinate axes. The query algorithm leverages the topology of the grid, resulting in much more efficient queries compared to a SimpleDB. The points do not need to be uniformly spaced along each coordinate direction. The point values can be specified in any order, as well as over a lower dimension than the spatial dimension. For example, one can specify a 2D grid in 3D space provided that the 2D grid is aligned with one of the coordinate axes.

SimpleGridDB uses a simple ASCII file to specify the variation of values in space. The file format is described in SimpleGridDB Format.

Note

You do not need to specify the data dimension when using a SimpleGridDB. The SimpleGriDB will determine the layout of the data from the spatial dimension and array of coordinates along each axis.

Pyre User Interface

See SimpleGridDB component.

Examples

We create a spatial database with three components of a displacement field over an xy surface in a UTM zone 10n geographic projection. We use an analytical function for the displacement field, \(\vec{u}\):

(4)\[\begin{align} u_x &= 2.0 + 4.0e-3*x \\ u_y &= 0.5 + 2.0e-3*y \\ u_z &= 1.0 + 3.0e-3*x - 1.0e-3*y \end{align}\]

You can create a SimpleGridDB data file manually in a text editor or generate the file using a Python script. In most cases, using a Python script is easier because you do not have to worry about the format of the file.

SimpleGridDB file

#SPATIAL_GRID.ascii 1
SimpleGridDB {
  num-x = 6
  num-y = 4
  num-z = 1
  space-dim = 3
  num-values = 3
  value-names =  displacement_x  displacement_y  displacement_z
  value-units =  m  m  m
  cs-data = geographic {
    crs-string = EPSG:32610
    space-dim = 3
  }
}
// x-coordinates
 -3.000000e+04 -2.000000e+04 -1.000000e+04  0.000000e+00  1.000000e+04  2.000000e+04
// y-coordinates
 -2.000000e+04 -1.000000e+04  0.000000e+00  1.000000e+04
// z-coordinates
  0.000000e+00
// data
 -3.000000e+04 -2.000000e+04  0.000000e+00 -1.180000e+02 -3.950000e+01 -6.900000e+01
 -2.000000e+04 -2.000000e+04  0.000000e+00 -7.800000e+01 -3.950000e+01 -3.900000e+01
 -1.000000e+04 -2.000000e+04  0.000000e+00 -3.800000e+01 -3.950000e+01 -9.000000e+00
  0.000000e+00 -2.000000e+04  0.000000e+00  2.000000e+00 -3.950000e+01  2.100000e+01
  1.000000e+04 -2.000000e+04  0.000000e+00  4.200000e+01 -3.950000e+01  5.100000e+01
  2.000000e+04 -2.000000e+04  0.000000e+00  8.200000e+01 -3.950000e+01  8.100000e+01
 -3.000000e+04 -1.000000e+04  0.000000e+00 -1.180000e+02 -1.950000e+01 -7.900000e+01
 -2.000000e+04 -1.000000e+04  0.000000e+00 -7.800000e+01 -1.950000e+01 -4.900000e+01
 -1.000000e+04 -1.000000e+04  0.000000e+00 -3.800000e+01 -1.950000e+01 -1.900000e+01
  0.000000e+00 -1.000000e+04  0.000000e+00  2.000000e+00 -1.950000e+01  1.100000e+01
  1.000000e+04 -1.000000e+04  0.000000e+00  4.200000e+01 -1.950000e+01  4.100000e+01
  2.000000e+04 -1.000000e+04  0.000000e+00  8.200000e+01 -1.950000e+01  7.100000e+01
 -3.000000e+04  0.000000e+00  0.000000e+00 -1.180000e+02  5.000000e-01 -8.900000e+01
 -2.000000e+04  0.000000e+00  0.000000e+00 -7.800000e+01  5.000000e-01 -5.900000e+01
 -1.000000e+04  0.000000e+00  0.000000e+00 -3.800000e+01  5.000000e-01 -2.900000e+01
  0.000000e+00  0.000000e+00  0.000000e+00  2.000000e+00  5.000000e-01  1.000000e+00
  1.000000e+04  0.000000e+00  0.000000e+00  4.200000e+01  5.000000e-01  3.100000e+01
  2.000000e+04  0.000000e+00  0.000000e+00  8.200000e+01  5.000000e-01  6.100000e+01
 -3.000000e+04  1.000000e+04  0.000000e+00 -1.180000e+02  2.050000e+01 -9.900000e+01
 -2.000000e+04  1.000000e+04  0.000000e+00 -7.800000e+01  2.050000e+01 -6.900000e+01
 -1.000000e+04  1.000000e+04  0.000000e+00 -3.800000e+01  2.050000e+01 -3.900000e+01
  0.000000e+00  1.000000e+04  0.000000e+00  2.000000e+00  2.050000e+01 -9.000000e+00
  1.000000e+04  1.000000e+04  0.000000e+00  4.200000e+01  2.050000e+01  2.100000e+01
  2.000000e+04  1.000000e+04  0.000000e+00  8.200000e+01  2.050000e+01  5.100000e+01

Python

import numpy

from spatialdata.spatialdb.SimpleGridAscii import createWriter
from spatialdata.geocoords.CSGeo import CSGeo

# Create the UTM zone 10n (WGS84 datum) coordinate system.
# The corresponding EPSG code is 32610. See https://epsg.io/32610.
cs = CSGeo()
cs.crsString = "EPSG:32610"
cs._configure()

# Create the coordinates of the points defining the spatial variation.
dx = 10.0e+3 # 10 km resolution
x1 = numpy.arange(-30000.0, +20000.0+0.5*dx, dx)
y1 = numpy.arange(-20000.0, +10000.0+0.5*dx, dx)
z1 = numpy.array([0.0])
x,y,z = numpy.meshgrid(x1, y1, z1, indexing="ij")
points = numpy.stack((x.ravel(),y.ravel(),z.ravel())).transpose()
del x,y,z
displacement = numpy.zeros(points.shape, dtype=numpy.float64)
displacement[:,0] = 2.0 + 4.0e-3*points[:,0]
displacement[:,1] = 0.5 + 2.0e-3*points[:,1]
displacement[:,2] = 1.0 + 3.0e-3*points[:,0] - 1.0e-3*points[:,1]

# Create a dictionary containing the data to write to the `SimpleDB` data file.
data = {
    "points": points,
    "x": x1,
    "y": y1,
    "z": z1,
    "coordsys": cs,
    "data_dim": 2,
    "values": [
        {
        "name": "displacement_x",
        "units": "m",
        "data": displacement[:,0],
        },{
        "name": "displacement_y",
        "units": "m",
        "data": displacement[:,1],
        },{
        "name": "displacement_z",
        "units": "m",
        "data": displacement[:,2],
        },
    ]
}

# Create the writer object and write the data file.
writer = createWriter("displacement.spatialdb")
writer.write(data)