Crop mapping

View larger image Figure 1: A chickpea crop growing amongst old stubble Enlarge image
Figure 1: A field photo of a mungbean crop sown with residual stubble taken on 2 March 2018 (left) and a Sentinel-2a satellite image of the same location, captured 19 February 2018 (right). The photo location and view direction are indicated by the red dot and arrow on the satellite image.
Image courtesy of the European Space Agency.

We use satellite imagery to map and monitor the groups of crops grown in Queensland’s broadacre cropping regions. Our remote sensing scientists have brought together and analysed satellite imagery back to 1987. The analysis produces two maps each year: one for the winter growing-season (June to October), and one for the summer growing-season (November to May).

In winter the mapped groups are:

  • cereal (e.g. wheat, barley, oats)
  • pulse (e.g. chickpea).

In summer the mapped groups are:

  • coarse-grain and pulse (e.g. sorghum, maize, mungbean)
  • cotton.

A ‘Bare soil’ group is also mapped in both summer and winter. This group describes parcels of land that have not been cropped and have little or no ground cover for a substantial part of a growing season.

View larger image Figure 2: Crop maps for an area in the south-west of Queensland in two consecutive growing seasons. Enlarge image
Figure 2: Crop maps for an area in the south-west of Queensland in two consecutive growing seasons.

How can crop maps be used?

Our satellite-derived crop maps deliver spatially comprehensive information that can be used for a range of agricultural production and strategic-planning activities. Some examples include:

  • identifying and protecting strategic cropping lands
  • improving our understanding of the water quality in our waterways
  • improving supply chains, including prioritising improvements to transportation infrastructure
  • informing land evaluations
  • directing response efforts and support, following natural disasters
  • studying the long-term effects of cropping on soil.

How are crop maps made?

To make a crop map, our scientists gather the satellite imagery for a year and growing-season of interest, and analyse it in a high-performance computing facility. The basic procedure is:

  1. Download Landsat and MODIS imagery from the United States Geological Survey, and the European Space Agency’s Sentinel-2 imagery, accessed from the Regional Copernicus Data Hub.
  2. Pre-process the imagery to correct for atmospheric and landscape effects, and exclude areas contaminated by clouds and cloud-shadows.
  3. Assemble the imagery as a time-series.
  4. Calculate the seasonal vegetation parameters across the landscape.
  5. Informed by field observations, use a model to predict the most likely group across the landscape, according to the particular growing-season and the seasonal vegetation parameters.
  6. Deliver the map to landholders, extension officers, private industry and government for a range of applications and purposes.

Step 4 involves applying a rigorously tested and validated statistical model.

The primary source of satellite imagery is from the Landsat mission. Landsat satellites have a 30-metre spatial resolution and a return interval of 16 days.

Since 2015, Sentinel-2 imagery is also included. Sentinel-2 has a return interval of up to five days, and helps to fill gaps in the Landsat time-series due to cloud. Sentinel-2 has a spatial resolution of 10 or 20 metres, but for ease of use in the crop model, it is resampled to 30-metre pixels to match Landsat. MODIS imagery, which has been available since 2000 and has a daily return interval, but a coarse spatial resolution of 250 metres, serves as a backup in cases of long gaps in the Landsat and Sentinel-2 imagery (i.e. > 4 weeks).

Where can I get the data?

Reports that summarise the cropping data on a lot-on-plan basis are available from the FORAGE reporting system. These reports are used in support of the Regional Planning Interest Act (RPI), 2014, and provide an estimate of the cropping history over a certain time period.

The crop maps are available at:

Contact us

For more information about crop mapping, contact the Science Leader via email, Remote Sensing Sciences.