Frequently Asked Questions¶
Which remote sensing products is the Biomass Proxy based on?¶
VanderSat Biomass Proxy is a fusion of active microwave imagery from the European Space Agency (ESA) Sentinel-1 satellite and optical images from its Sentinel-2 satellites.
How does cloud cover affect the quality of the product?¶
An image can be provided daily. However, if for a long period of time (multiple weeks) Sentinel-2 images are unavailable, the signal is dominated by the microwave signal. Since these satellites have a high repeat frequency, the temporal resolution of the overall product is hardly affected. However, in the case that this shortage of Sentinel-2 is coincident with a drastic change event within the field (e.g. harvest, disease), the spatial accuracy may suffer as it is more challenging to capture these events with high spatial detail using microwave data alone.
The extent of any quality reduction will be quantified in the companion quality layer (coming soon).
What is the unit of measurement?¶
We use a relative measure of biomass, so each pixel value has a value of 0 (low biomass) to 1 (high biomass). 1 is where the signal is saturated, it is rare, but it sometimes happens when you have a very dense vegetation cover (e.g. LAI > 5) but it happens in dense forests. As the Biomass Proxy is designed for agricultural practices, this does have a very limited effect on the intended applicability of the product.
What is the spatial resolution?¶
The resolution of the Biomass Proxy is 10 m x 10 m. See Biomass Proxy for more product specifications.
Does the Biomass saturate at high values?¶
The signal can get saturated, it is rare and only happens at very dense vegetation covers (e.g. LAI > 5). As the Biomass Proxy is designed for agricultural purposes, this does not affect the intended applicability of the product.
For what regions on Earth is the product available?¶
The Biomass Proxy can be processed for any (agricultural) location on Earth. However, at this moment, the Biomass Proxy is fully operational in Canada, the United States, and Ukraine. Brazil, Argentina, Germany, and the Netherlands will become available later in 2021. Beyond that, New regions will become available in late 2021 based on customer demand.
How does biomass compare with yield?¶
Biomass is an important indicator of crop yield. Nonetheless it is also different from yield depending on crop type. The biomass that is measured corresponds with the full column of above-ground biomass. The actual yield obtained is measured in units of production e.g. kg/m2 corn (which is not the same as kg/m2 corn plant, including the stems and the leaves). Often, through strong correlations with yield (>0.7), biomass can to a certain degree be translated to yield and has a predictive skill.
Does it work in grassland?¶
Absolutely. The Biomass Proxy can accurately monitor changes in biomass in areas of pasture and grassland, and is sensitive enough to produce a characteristic signal for each field.
Has the product been validated?¶
The product has been extensively tested together with our launching customer (xarvio™ Digital Farming Solutions, BASF) in three regions – Europe, North America and South America. We are currently broadening the validation study with different scientific groups and will soon be able to share the results.
What are the effects of frozen ground / snow cover?¶
Frozen ground and snow cover impacts both optical and microwave signals. This has been accounted for and taken care of by the algorithm and now rarely affects the signal in the growing season.
Could harvest be detected?¶
Yes, field harvest events can clearly be seen in the timeseries of the Biomass Proxy. However, in order to verify that a low and outlying biomass value is indeed due to harvest and not other technical factors, we may require and additional overpass, which would delay harvest detection
How does the Biomass Proxy compare to NDVI? What are the advantages over NDVI?¶
Unlike Normalized Difference Vegetation Index (NDVI), which is not available on cloudy days and only measures spectral greenness, the Biomass Proxy measures biophysical parameters and water content in vegetation continually to accurately calculate all stages of crop growth during the entire growing season. NDVI is based on optical satellite data so is unavailable when it is cloudy. VanderSat Biomass Proxy on the other hand also makes use of microwave data, so is also available even when there is cloud cover. NDVI and Biomass Proxy can complement each other because they look at different biophysical characteristics of the plant. By combining the NDVI and Biomass Proxy you have a better view on your crop conditions.
What is the difference between the Biomass Proxy and Vandersat Vegetation Optical Depth (VOD)?¶
The Biomass Proxy is a fusion of optical and microwave data and is at a 10 x 10 m spatial resolution. However the historical archive is only available back to 2017. On the other hand, the VOD product is based only on passive microwaves signal but is available back until 2002. VOD also has a lower spatial resolution, so is typically used to calculate anomalies in vegetation water content on a more regional scale, taking advantage of the long historical record.
What makes the product unique?¶
There is no other globally available and fully operational product like the Biomass Proxy that observes biomass with this revisit time, accuracy and spatial resolution. The basis for the product is found in the VanderSat’s wealth of experience in remote sensing, combining active microwave data from the European Space Agency (ESA) Sentinel-1 satellites and optical images from its Sentinel-2 satellites.
How is the data delivered?¶
Data is delivered through our API. You can upload shapefiles into your allowed area and directly download via the API time series for each field in .csv format, or download spatial data in NetCDF or GeoTiff format. The data can also be viewed in-browser in the VanderSat viewer, where API requests can also be made and managed. (see API User Guide for more details).
When can I expect a new image? How soon after a satellite overpass is the data available?¶
A new update will be available in your account at 6am local solar time, every day, based on the most recent images from all of the satellite data sources.
How long is the historical record?¶
In addition to our NRT offering, we are also able to provide a historical archive of Biomass. Any service including historical data will include data from april 1st 2020 on. It is also possible to process the full archive back to 2017, at additional cost.
What is the cost/ how does pricing work?¶
Prices are set on the basis of per hectare, per year, and are determined by the size and duration of the customer commitment and the required historical record.
How can we (“prospect/customer”) validate the VanderSat Biomass Proxy¶
The Biomass Proxy could be validated against your or your customers’ in-field Biomass. We are happy to exchange data and work together with you on this sort of validation activity as part of a proof of concept study before a commercial deal.
Is there a quality metric available?¶
Within VanderSat we are currently working on a data quality layer which will eventually be packaged together with the Biomass Proxy.