Completed works
The main tool for this expert examination is the vegetation index (NDVI). This indicator can show the presence of plants and the stage of vegetation they are in. The index is obtained based on the interaction operation with different spectral ranges of remote sensing data. Plants absorb the red zone of the spectrum with their green mass and reflect the near-infrared. The resolution of the satellite images was 10 meters per pixel, and the wheat field had an area of 620 hectares. The scale of the images allowed us to observe the main stages of plant development.
Using higher resolution imagery on the site can help determine the presence of weeds or diseases, assess germination and plant growth, and even predict the productivity of crop rotation fields.
The main goal was to track the growth and development dynamics of the crop and determine the harvesting time.
We took satellite images from March-April 2020 and June 2020. The processing of the satellite images and measurement of the vegetation index were carried out in several software packages. Preliminary operations were performed in QGIS (version 3.24.2) and ENVI (Harris).
The image preparation consisted of the following tasks:
- Finding and extracting the required plot from the entire area;
- Combining panchromatic and multispectral channels to obtain a high-quality color image;
- Atmospheric and radiometric corrections;
- Performing geocoding, or tying the image to the global coordinate system WGS 84 (resulting in each pixel on the image corresponding to the required points on the ground).
This level of processing is necessary for quantitative and qualitative analysis based on NDVI. It is important to understand that atmospheric correction helps reduce error when assessing the vegetative state of vegetation in the fields.
The NDVI measurement was performed in the ArcGIS (ESRI) program.
NDVI values in the images from August and September clearly showed that the fields had no vegetation and the level of vegetation was absent.
NDVI values in the images from October showed that there was vegetation on the fields and the vegetation level on each field was high.
During the spring period, it was established that at that time the field had wheat seedlings in the tillering phase, not crop residues or stubble (which are plant residues that improve soil fertility). At the end of May, the analysis of satellite images showed a high level of vegetative activity. This means that the wheat was in the stem elongation and heading stages.
The images from early June 2020 showed us the harvesting process during this period. The use of high-resolution images allowed us to decipher the traces of agricultural machinery in the fields during the harvest period.
Thanks to the spectral method of satellite image analysis, GEO INNOTER specialists deciphered the period of winter wheat sowing, seedlings, growth, crop ripening, and harvesting.