r.profile - GRASS GIS manual

NAME

r.profile - Outputs the raster map layer values lying on user-defined line(s).

KEYWORDS

SYNOPSIS

r.profile

r.profile --help

r.profile [-gc] input=name [output=name] [coordinates=east,north[,east,north,...]] [file=name] [resolution=float] [null_value=string] [units=string] format=name [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags:

-g: Output easting and northing in first two columns of four column output
-c: Output RRR:GGG:BBB color values for each profile point
--overwrite: Allow output files to overwrite existing files
--help: Print usage summary
--verbose: Verbose module output
--quiet: Quiet module output
--ui: Force launching GUI dialog

Parameters:

input=name [required]: Name of input raster map
output=name: Name of file for output (use output=- for stdout); Default: -
coordinates=east,north[,east,north,...]: Profile coordinate pairs
file=name: Name of input file containing coordinate pairs; Use instead of the 'coordinates' option. "-" reads from stdin.
resolution=float: Resolution along profile (default = current region resolution)
null_value=string: String representing NULL value; Default: *
units=string: Units; If units are not specified, current project units are used. Meters are used by default in geographic (latlon) projects.; Options: meters, kilometers, feet, miles
format=name [required]: Output format; Options: plain, json; Default: plain; plain: Plain text output; json: JSON (JavaScript Object Notation)

DESCRIPTION
OUTPUT FORMAT
NOTES
EXAMPLES
SEE ALSO
AUTHOR

DESCRIPTION

This program outputs two or four column (with -g) data to stdout or an ASCII file. The default two column output consists of cumulative profile length and raster value. The optional four column output consists of easting, northing, cumulative profile length, and raster value. Profile end or "turning" points can be set manually with the coordinates argument. The profile resolution, or distance between profile points, is obtained from the current region resolution, or can be manually set with the resolution argument.

The coordinates parameter can be set to comma separated geographic coordinates for profile line endpoints. Alternatively the coordinate pairs can be piped from the text file specified by file option, or if set to "-", from stdin. In these cases the coordinate pairs should be given one comma separated pair per line.

The resolution parameter sets the distance between each profile point (resolution). The resolution must be provided in GRASS database units (i.e. decimal degrees for Lat Long databases and meters for UTM). By default r.profile uses the resolution of the current GRASS region.

The null parameter can optionally be set to change the character string representing null values.

OUTPUT FORMAT

The multi column output from r.profile is intended for easy use in other programs. The output can be piped (|) directly into other programs or saved to a file for later use. Output with geographic coordinates (-g) is compatible with v.in.ascii and can be piped directly into this program.

r.profile -g input=elevation coordinates=... | v.in.ascii output=elevation_profile separator=space

The 2 column output is compatible with most plotting programs.

The optional RGB output provides the associated GRASS colour value for each profile point.

Option units enables to set units of the profile length output. If the units are not specified, current coordinate reference system's units will be used. In case of geographic CRS (latitude/longitude), meters are used as default unit. Finally, the output from r.info can be output in JSON by passing the format=json option.

NOTES

The profile resolution is measured exactly from the supplied end or "turning" point along the profile. The end of a profile segment will be an exact multiple of the profile resolution and will therefore not always match the end point coordinates entered for the segmanet.

To extract the numbers in scripts, following parameters can be used:

r.profile input=dgm12.5 coordinates=3570631,5763556 2>/dev/null

This filters out everything except the numbers.

EXAMPLES

Extraction of values along profile defined by coordinates (variant 1)

Extract a profile with coordinates (wayoints) provided on the command line (North Carolina data set):

g.region raster=elevation -p
r.profile -g input=elevation output=profile_points.csv \
          coordinates=641712,226095,641546,224138,641546,222048,641049,221186

This will extract a profile along the track defined by the three coordinate pairs. The output file "profile_points.csv" contains east,north,distance,value (here: elevation).

Extraction of values along profile defined by coordinates (variant 2)

Coordinate pairs can also be "piped" into r.profile (variant 2a):

r.profile elevation resolution=1000 file=- << EOF
641712,226095
641546,224138
641546,222048
641049,221186
EOF

Coordinate pairs can also be "piped" into r.profile (variant 2b):

echo "641712,226095
641546,224138
641546,222048
641049,221186" > coors.txt
cat coors.txt | r.profile elevation resolution=1000 file=-

The output is printed into the terminal (unless the output parameter is used) and looks as follows:

Using resolution: 1000 [meters]
Output columns:
Along track dist. [meters], Elevation
Approx. transect length: 1964.027749 [meters]
 0.000000 84.661507
 1000.000000 98.179062
Approx. transect length: 2090.000000 [meters]
 1964.027749 83.638138
 2964.027749 89.141029
 3964.027749 78.497757
Approx. transect length: 995.014070 [meters]
 4054.027749 73.988029

JSON Output

r.profile -g input=elevation coordinates=641712,226095,641546,224138,641546,222048,641049,221186 -c format=json resolution=1000

The output looks as follows:

[
    {
        "easting": 641712,
        "northing": 226095,
        "distance": 0,
        "elevation": 84.661506652832031,
        "red": 113,
        "green": 255,
        "blue": 0
    },
    {
        "easting": 641627.47980925441,
        "northing": 225098.57823319823,
        "distance": 1000.0000000000125,
        "elevation": 98.179061889648438,
        "red": 255,
        "green": 241,
        "blue": 0
    },
    {
        "easting": 641546,
        "northing": 224138,
        "distance": 1964.0277492948007,
        "elevation": 83.638137817382812,
        "red": 100,
        "green": 255,
        "blue": 0
    },
    {
        "easting": 641546,
        "northing": 223138,
        "distance": 2964.0277492948007,
        "elevation": 89.141029357910156,
        "red": 169,
        "green": 255,
        "blue": 0
    },
    {
        "easting": 641546,
        "northing": 222138,
        "distance": 3964.0277492948007,
        "elevation": 78.497756958007812,
        "red": 35,
        "green": 255,
        "blue": 0
    },
    {
        "easting": 641546,
        "northing": 222048,
        "distance": 4054.0277492948007,
        "elevation": 73.988029479980469,
        "red": 0,
        "green": 249,
        "blue": 17
    }
]

Using JSON output with Python for plotting data

The JSON output makes for ease of integration with popular python data science libraries. For instance, here is an example of creating a scatterplot of distance vs elevation with color coding.

import grass.script as gs
import pandas as pd
import matplotlib.pyplot as plt

# Run r.profile command
elevation = gs.read_command(
    "r.profile",
    input="elevation",
    coordinates="641712,226095,641546,224138,641546,222048,641049,221186",
    format="json",
    flags="gc"
)

# Load the JSON data into a dataframe
df = pd.read_json(elevation)

# Convert the RGB color values to hex format for matplotlib
df["color"] = df.apply(lambda x: "#{:02x}{:02x}{:02x}".format(int(x["red"]), int(x["green"]), int(x["blue"])), axis=1)

# Create the scatter plot
plt.figure(figsize=(10, 6))
plt.scatter(df['distance'], df['elevation'], c=df['color'], marker='o')
plt.title('Profile of Distance vs. Elevation with Color Coding')
plt.xlabel('Distance (meters)')
plt.ylabel('Elevation')
plt.grid(True)
plt.show()

AUTHOR

Bob Covill

SOURCE CODE

Available at: r.profile source code (history)

Latest change: Tuesday Jul 02 15:24:52 2024 in commit: 7f4aabffb350c6d12ef5d27f954a95f7d1de3be4