Processor RasterExtract#

Table of Contents#

  1. What is Processor RasterExtract

    1. Edge Cases

  2. Processor RasterExtract Example

    1. Setup BDT

    2. Input Data

    3. Running Processor RasterExtract

Part 1: What is Processor RasterExtract#

RasterExtract is a processor that enriches point geometries with the values of raster cells the point overlaps.

This processor requires additional libraries not included with the BDT jar. See the Setup for Raster guide for the respective environment to use this processor.

Overview of raster extract

Edge Cases#

If a point lays on a border of a raster cell, the processor will always look to the cell below it.

If a point lays on a corner of a raster cell, the processor will always look to the lower right cell.

If there is no cell below or to the lower right, the point is considered outside of the raster bounds and no value will be emitted.

Overview of raster extract

Part 2: Processor RasterExtract Example#

Setup BDT#

[1]:

import bdt
bdt.auth("../bdt.lic")
from bdt import processors as P

BDT has been successfully authorized!

            Welcome to
             ___    _                ___         __             ______             __   __     _   __
            / _ )  (_)  ___ _       / _ \ ___ _ / /_ ___ _     /_  __/ ___  ___   / /  / /__  (_) / /_
           / _  | / /  / _ `/      / // // _ `// __// _ `/      / /   / _ \/ _ \ / /  /  '_/ / / / __/
          /____/ /_/   \_, /      /____/ \_,_/ \__/ \_,_/      /_/    \___/\___//_/  /_/\_\ /_/  \__/
                      /___/

BDT python version: v3.4.0-develop-12-ge79ea377
BDT jar version: v3.4.0-develop-12-ge79ea377

Input Data#

Create a DataFrame of Point geometries with IDs. Ensure the DataFrame has geometry metadata.

[6]:

point_df = spark.createDataFrame([
  (1, 0.0, 0.0),
  (2, 1.0, 1.0),
  (3, 0.5, 0.7),
  (4, 2.5, 1.5),
], schema="ID int, X double, Y double") \
    .selectExpr("ID", "ST_MakePoint(X, Y) AS SHAPE") \
    .withMeta("Point", 4326)

[7]:

point_df.show(truncate=False)

+---+--------------------------------------------------------------------------------------+
|ID |SHAPE                                                                                 |
+---+--------------------------------------------------------------------------------------+
|1  |{[01 01 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00], 0.0, 0.0, 0.0, 0.0}|
|2  |{[01 01 00 00 00 00 00 00 00 00 00 F0 3F 00 00 00 00 00 00 F0 3F], 1.0, 1.0, 1.0, 1.0}|
|3  |{[01 01 00 00 00 00 00 00 00 00 00 E0 3F 66 66 66 66 66 66 E6 3F], 0.5, 0.7, 0.5, 0.7}|
|4  |{[01 01 00 00 00 00 00 00 00 00 00 04 40 00 00 00 00 00 00 F8 3F], 2.5, 1.5, 2.5, 1.5}|
+---+--------------------------------------------------------------------------------------+

Running Processor RasterExtract#

  • Let’s run Processor RasterExtract using the same simple.tif pictured above.

[8]:

out_df = P.raster_extract(point_df, "simple.tif", miid_field="ID", shape_field="SHAPE")

[10]:

out_df.show()

+---+-----------------+
| ID|            value|
+---+-----------------+
|  2|6.481858253479004|
|  3|2.502182722091675|
+---+-----------------+

  • Point 1 was not emitted since it was on a raster cell corner and no cell was found to its lower right.

  • Point 4 was not emitted since it was outside of the raster bounds.

Overview of raster extract

The resulting dataframe can be joined back to the original dataframe to enrich the point geometries with the raster cell values.

[11]:

out_df.join(point_df, "ID").show(truncate=False)

+---+-----------------+--------------------------------------------------------------------------------------+
|ID |value            |SHAPE                                                                                 |
+---+-----------------+--------------------------------------------------------------------------------------+
|2  |6.481858253479004|{[01 01 00 00 00 00 00 00 00 00 00 F0 3F 00 00 00 00 00 00 F0 3F], 1.0, 1.0, 1.0, 1.0}|
|3  |2.502182722091675|{[01 01 00 00 00 00 00 00 00 00 00 E0 3F 66 66 66 66 66 66 E6 3F], 0.5, 0.7, 0.5, 0.7}|
+---+-----------------+--------------------------------------------------------------------------------------+