Using the 'gdalinfo' Command (with examples)

The ‘gdalinfo’ command is a powerful tool within the GDAL (Geospatial Data Abstraction Library) software that allows users to obtain various information about a GDAL-supported raster dataset. This information can be crucial for understanding the characteristics and properties of a raster dataset, such as its format, spatial parameters, data type, and metadata. The ‘gdalinfo’ command can also be used to extract histogram values and analyze Web Map Services (WMS). In this article, we will explore different use cases of the ‘gdalinfo’ command, along with relevant code examples, motivations, explanations, and example outputs.

1: Listing all supported raster formats

gdalinfo --formats

Motivation: It is important to know the supported raster formats by GDAL in order to determine if a specific format is compatible with the library. This becomes relevant when choosing a raster dataset to work with, or when attempting to convert a raster dataset to a different format.

Explanation: The ‘–formats’ option instructs the ‘gdalinfo’ command to list all supported raster formats. This provides users with a comprehensive list of raster formats compatible with GDAL.

Example Output:

Supported Formats:
  VRT (rw+v): Virtual Raster
  GTiff (rw+vs): GeoTIFF
  ...

2: Listing information about a specific raster dataset

gdalinfo path/to/input.tif

Motivation: When working with a specific raster dataset, it is essential to gather detailed information about the dataset such as its resolution, extent, coordinate system, and metadata. This information aids in understanding the dataset’s spatial characteristics and can guide subsequent analysis or processing steps.

Explanation: The ‘gdalinfo’ command with a specific raster dataset path provides extensive information about the dataset. The ‘path/to/input.tif’ is a placeholder that should be replaced with the actual file path of the desired raster dataset.

Example Output:

Driver: GTiff/GeoTIFF
Files: path/to/input.tif
Size is 512, 512
Coordinate System is:
...

3: Listing information about a specific raster dataset in JSON format

gdalinfo -json path/to/input.tif

Motivation: Obtaining information about a raster dataset in JSON format can be useful for automation, parsing, or exchanging data between different software applications or systems. JSON is a widely accepted and flexible data format that can be easily handled by programming languages.

Explanation: The ‘-json’ option instructs ‘gdalinfo’ to output the raster dataset information in JSON format, which allows for structured data representation. By including this option along with the raster dataset path, the command will produce the information in a JSON-encoded format.

Example Output:

{
  "description": "path/to/input.tif",
  "driverShortName": "GTiff",
  ...
}

4: Showing histogram values of a specific raster dataset

gdalinfo -hist path/to/input.tif

Motivation: Understanding the statistical distribution of pixel values within a raster dataset can provide insights into the overall data characteristics. Calculating and visualizing histograms can reveal patterns, detect outliers, and aid in subsequent analysis or decision-making processes.

Explanation: The ‘-hist’ option prompts ‘gdalinfo’ to calculate the histogram values for the specified raster dataset. The command should be executed with the path to the desired raster dataset.

Example Output:

  ...
  1000: 0
  2000: 0
  3000: 182
  4000: 509
  ...

5: Listing information about a Web Map Service (WMS)

gdalinfo WMS:https://services.meggsimum.de/geoserver/ows

Motivation: Understanding the properties and capabilities of Web Map Services (WMS) is crucial when integrating them into GIS applications or analyzing data from online sources. Listing information about a WMS allows users to view its supported layers, coordinate systems, and other important details.

Explanation: By utilizing the ‘gdalinfo’ command with the ‘WMS:’ prefix followed by the URL of the desired WMS, relevant information about the service will be provided. The example URL used here is just a placeholder and should be replaced with an actual WMS URL.

Example Output:

Driver: WMS/OGC Web Map Service
Files: none associated
Layer name: layer1
...

6: Listing information about a specific dataset of a Web Map Service (WMS)

gdalinfo WMS:https://services.meggsimum.de/geoserver/ows -sd 4

Motivation: When working with a Web Map Service (WMS) that provides multiple datasets or layers, it becomes essential to retrieve detailed information about a particular dataset of interest. This information aids users in understanding the dataset’s spatial extent, resolution, coordinate system, and other important details.

Explanation: The ‘gdalinfo’ command with the ‘WMS:’ prefix and a URL of the WMS, along with the ‘-sd’ option and a dataset index, allows users to obtain relevant information about a specific dataset. The dataset index refers to the position of the dataset within the WMS service, with 0 being the first dataset.

Example Output:

Driver: WMS/OGC Web Map Service
Files: none associated
Layer name: layer4
...

In conclusion, the ‘gdalinfo’ command is a versatile tool that provides valuable information about GDAL-supported raster datasets and Web Map Services. These use cases presented in this article showcase how the command can assist in identifying supported raster formats, obtaining dataset information, extracting histogram values, and exploring the characteristics of Web Map Services. By incorporating the ‘gdalinfo’ command into one’s workflow, users can gain deeper insights into their geospatial data and make more informed decisions.