Enhanced Resolution
Soil Water Content is no longer sold at 20 m and 100 m resolution. Active contracts remain fully supported through their remaining terms, and the core infrastructure will officially sunset in April 2028. Upon renewal, please contact your Account Executive to transition to our 1000 m product variant or explore other suitable alternatives for your specific use case.
Soil Water Content 100 m
Product Specifications
Table 1: SWC 100 m product specification
| Data Resource | SWC 100 m L band | SWC 100 m C band | SWC 100 m X band |
|---|---|---|---|
| Source ID | SWC-SMAP-L_V2.0_100 | SWC-AMSR2-C_V2.0_100 | SWC-AMSR2-X_V2.0_100 |
| Satellites Used | AMSR-2, SMAP, Sentinel-2 | AMSR-2, Sentinel-2 | AMSR-2, Sentinel-2 |
| Band | L band | C band | X band |
| Version | 2.0 | 2.0 | 2.0 |
| Unit | m³/m³ | m³/m³ | m³/m³ |
| Sensing Depth | ~5 cm | ~2 cm | ~1 cm |
| Pixel Size | 100x100 m | 100x100 m | 100x100 m |
| Temporal Resolution | 0° latitude: 137 to 183 observations per year 40° latitude: 183 to 228 observations per year | 0° latitude: 205 to 228 observations per year 40° latitude: 274 to 292 observations per year | 0° latitude: 205 to 228 observations per year 40° latitude: 274 to 292 observations per year |
| Overpass Time | 06:00 local solar time | 01:30 local solar time | 01:30 local solar time |
| Geographical Coverage | Global | Global | Global |
| Data Availability | 2017-07-01 - Present Data Gaps: 2019-06-19 to 2019-07-24 2022-08-05 to 2022-09-24 2022-11-16 to 2022-11-18 | 2017-07-01 - Present | 2017-07-01 - Present |
| NRT latency (p90) | 72 hours | 48 hours | 48 hours |
| Archive latency | Within 30 days after creating a subscription | Within 30 days after creating a subscription | Within 30 days after creating a subscription |
The sensing depth described in the table is an estimation of the average condition. Several studies (For example, Schmugge et al., 1986; Wang et al., 1987; Owe et al., 1998) have shown that microwave-based soil water content penetration depth depends on the soil water content conditions and frequency. At 1.41 GHz the penetration depth varies from approximately 10 cm to 1 m for soil conditions ranging from saturated to dry, whereas at 10.7 GHz the penetration depth varies from less than a few mm to a little over 2 cm for similar conditions. Thus, the drier the soil, the deeper the sampling depth.
Asset Properties
Each SWC 100 m observation is delivered as a SWC data asset (*swc.tif) with metadata provided in a separate quality flag asset (*swc-qf.tif).
Table 2: Asset properties of SWC 100 m data resources
| Asset Name | Band Name | Unit | Type | Typical Range | No Data Value | Scale | Format |
|---|---|---|---|---|---|---|---|
| swc | Band 1 | m3/m3 | UINT16 | 0 - 1 | 65535 | 0.001 | GeoTIFF |
| swc | Band 2 | m3/m3 | UINT16 | 0 - 1 | 65535 | 0.001 | GeoTIFF |
| swc-qf | Band 1 | unitless | UINT16 | NA | 0 | 1 | GeoTIFF |
Enhancements Using Optical Data
The microwave observations are further downscaled to a spatial resolution of 100 m based on the Normalized Difference Shortwave Infrared (NDSWIR) index. This index is constructed from Near-Infrared (NIR) and Shortwave Infrared (SWIR) bands of Sentinel-2, namely B08 (842 nm) and B11 (1610 nm).
Several studies (Lobell & Asner 2002, Fensholt and Sandholt 2003, Sadeghi et al. 2017, Yue et al. 2019) found that soil and plant water content significantly affect the reflection in the SWIR part of the spectrum. The NIR reflectance is influenced by the internal structure and dry matter content of leaves, but not by water content. By combining SWIR, which responds to water content, with NIR reflectance, we can more accurately retrieve water content from the reflectance data (Gao 1996, Ceccato et al. 2001).
Planet produces a daily NDSWIR composite using a backward Gaussian weighted distribution. This composite integrates into the downscaling framework by attributing the weight of a brightness temperature to each pixel within the footprint. The output format remains similar to that of the downscaling algorithm without NDSWIR input.
The Sentinel-2 data is extracted from L2A - Bottom of the atmosphere (BOA) - reflectance in the Sentinel-2 dataset documentation.
Input Data
Table 3: List of inputs for SWC 100 m production
| Product | Description |
|---|---|
| Brightness Temperature L band | Soil Moisture Active Passive (SMAP) Level-1B Radiometer Half-Orbit Time-Ordered L band Brightness Temperatures, Version 5 (downloaded from NSIDC in HDF5 format). This Level-1B product provides calibrated estimates of time-ordered geolocated brightness temperatures at 1.41 GHz with a footprint size of 39x47 km. SMAP L band brightness temperatures are referenced to the Earth's surface with undesired and erroneous radiometric sources removed. Data has been available since April 2015 with a latency of 12 hours. Detailed information is available here. |
| Brightness Temperature X band | Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and Advanced Microwave Scanning Radiometer 2 (AMSR-2) Level-1B Radiometer X band Brightness Temperatures (downloaded from JAXA G-portal in HDF5 format). This Level-1B product provides calibrated estimates of geolocated brightness temperatures at 10.7 GHz with a footprint size of 24x42 km. Data has been available from July 2002 to October 2011 (AMSR-E) and from June 2012 (AMSR-2) up to now with a latency of 12 hours. Detailed information is available here |
| Brightness Temperature C band | AMSR-E and AMSR-2 Level-1B Radiometer C band Brightness Temperatures (downloaded from JAXA G-portal in HDF5 format). This Level-1B product provides calibrated estimates of geolocated brightness temperatures at 6.9 GHz with a footprint size of 35x62 km. Data has been available from July 2002 to October 2011 (AMSR-E) and from June 2012 (AMSR-2) up to now with a latency of 12 hours. Detailed information is available here. |
| Brightness Temperature Ka band | AMSR-E and AMSR-2 Level-1B Radiometer Ka band Brightness Temperatures (downloaded from JAXA G-portal in HDF5 format). This Level-1B product provides calibrated estimates of geolocated brightness temperatures at 36.5 GHz with a footprint size of 7x12 km. Data has been available from July 2002 to October 2011 (AMSR-E) and from June 2012 (AMSR-2) up to now with a latency of 12 hours. Detailed information is available here. |
| Brightness Temperature W band | AMSR-E and AMSR-2 Level-1B Radiometer W band Brightness Temperatures (downloaded from JAXA G-portal in HDF5 format). This Level-1B product provides calibrated estimates of geolocated brightness temperatures at 89 GHz with a footprint size of 3x5 km. Data has been available from July 2002 to October 2011 (AMSR-E) and from June 2012 (AMSR-2) up to now with a latency of 12 hours. Detailed information is available here. |
| Reflectances SWIR and NIR | Sentinel-2 Level-2A reflectance data for two bands: SWIR (shortwave infrared around 1610 nm) and NIR (near infrared around 842 nm). |
| Digital Elevation Model | Digital elevation model (DEM) static map resampled at 100 m based on the Copernicus DEM GLO-90 product covering the full global landmass of the time frame of data acquisition (2011-2015). Detailed information is available in the link. |
| Land Cover Map | Custom global land classification including permanent water bodies based on the Copernicus Global Surface Water Bodies product from PROBA-V. Detailed information is available here |
| Soil Map | Soil property maps resampled at 100 m based on the SoilGrids product. SoilGrids was funded by the core funding of ISRIC with additional support from the EUH2020 CIRCASA project. Detailed information is available here, |
Metadata
Quality flag assets (*swc-qf.tif) provide metadata for each pixel using bitwise flags. Critical flags indicate unreliable data, with corresponding pixels in band 1 of the SWC asset (*swc.tif) set to the no data value. The replaced SWC value can be found in band 2 of the SWC asset. Non-critical flags indicate that the data can be used with caution, taking into account the flag description.
Critical and non-critical flags are described in the tables below. For more information on how to access the quality flag asset, check out subscribing to planetary variables.
Table 4: Non-critical flags
| Bit | Flag layer | Description |
|---|---|---|
| 1 | Dense vegetation | The retrieved soil water content is less reliable over dense vegetation cover. |
| 2 | Low soil water content | The retrieved soil water content is lower than the estimated wilting point. |
| 3 | High soil water content | The retrieved soil water content is higher than the estimated porosity. |
| 4 | Possible severe precipitation | Part of the footprints touch an area flagged as severe precipitation. |
| 5 | Possible RFI | Footprints are contaminated for less than 25% with Radio Frequency Interference (RFI). RFI occurs when human-made transmitters emit in the same frequencies and thus disrupt the radiometer measurements of the natural microwave emission. |
| 7 | Possible frozen soil | The soil may be frozen. These are pixels with a soil temperature between -10°C and 0°C. |
Table 5: Critical flags
| Bit | Flag layer | Description |
|---|---|---|
| 6 | Statistical outlier | The underlying footprint is considered a statistical outlier. |
| 8 | Frozen soil | The soil is frozen. Pixels with a soil temperature below -10°C. A conservative value of -10°C was chosen to avoid masking valid data. |
| 9 | Severe precipitation | Severe precipitation is detected. |
| 10 | Vegetation too dense | The vegetation cover is too dense for the algorithm to reliably retrieve soil water content. |
| 11 | No overpass | The satellite did not pass over. |
| 12 | RFI | Footprints are contaminated for more than 25% with Radio Frequency Interference (RFI). RFI occurs when human-made transmitters emit in the same frequencies and thus disrupt the radiometer measurements of the natural microwave emission. |
| 13 | Instrumental flaws | Unrealistic values due to instrumental flaws. If the brightness temperature at 36.5 GHz V produces values either over 400K or under 0.9 * the water temperature, the data is considered as unrealistic and is removed. |
| 14 | Out of valid range | Soil water content values are outside the valid range, meaning under 0 m3/m3 or above 1 m3/m3. |
| 15 | Open water | Soil water content is not defined over water. |
| 16 | Brightness temperature residuals too high | The LPRM model could not find a soil water content value that is consistent with all provided input data. |
Figure 1: An example of two quality flags for a region around Nantes, France. The image shows critical flags 'open water' and 'no overpass' overlaid on SWC 100 m.
The following Python script converts a quality flag pixel value into a list of corresponding quality flags. Note that one pixel may have multiple flags applied to it.
# swc_quality_flags.py
import argparse
SWC_QUALITY_FLAGS = {
1: "Dense vegetation",
2: "Low soil water content",
3: "High soil water content",
4: "Possible severe precipitation",
5: "Possible RFI",
6: "Statistical outlier (critical flag)",
7: "Possible frozen soil",
8: "Frozen Soil (critical flag)",
9: "Severe precipitation (critical flag)",
10: "Vegetation too dense (critical flag)",
11: "No overpass (critical flag)",
12: "RFI (critical flag)",
13: "Instrumental flaws (critical flag)",
14: "Out of valid range (critical flag)",
15: "Open water (critical flag)",
16: "Brightness temperature residuals too high (critical flag)",
}
def convert_to_quality_flags(decimal_value: int) -> list[str]:
binary_string = format(decimal_value, "016b")
reversed_binary_string = binary_string[::-1]
return [
f"{i}. {SWC_QUALITY_FLAGS.get(i, 'Unused flag')}"
for i, bit in enumerate(reversed_binary_string, start=1) if bit == "1"
]
if __name__ == "__main__":
parser = argparse.ArgumentParser(description="Convert a decimal value to quality flags.")
parser.add_argument("decimal_value", type=int, help="The decimal value to convert.")
args = parser.parse_args()
flags = convert_to_quality_flags(args.decimal_value)
print(*flags, sep="\n")
that you can call as follows, using value 32770 as example:
> python swc_quality_flags.py 32770
2. Low soil water content
16. Brightness temperature residuals too high (critical flag)
Other Limitations
- Cloud cover hinders the optical observations by Sentinel-2 that are used for the SWC 100 m products. The downscaling can therefore only be updated when we obtain a cloud-free observation and the SWC data may suddenly increase or decrease after a long spell of no observations.
Frequently Asked Questions
What is the difference between the SWC 20 m, 100 m, and 1000 m products?
Our SWC 1000 m product is based on our patented disaggregation method where we make optimum use of the overlapping satellite footprints to refine the resolution from 36 km to 1 km. The SWC 100 m product also uses the NIR and SWIR band from Sentinel-2 to add more spatial constraints to our disaggregation method.
Why does the SWC 1000 m product show a higher correlation with in-situ measurements than the SWC 100 m product?
Sometimes, customers compare our SWC products with in-situ measurements and find that the SWC 1000 m products perform better than the SWC 100 m products. This can be explained by the method used to enhance the spatial resolution. The SWC 1000 m product uses passive microwave observations, and has a temporal resolution of about 2 days, depending on the microwave band used and the latitude.
As a result, the SWC 1000 m product sees a lot of the temporal variations in SWC which are also caught by the in-situ sensor. For the enhanced-resolution products, we combine the passive microwave observations with infrared observations from the Sentinel-2 satellite. The infrared observations have a repeat cycle of about 5 days, depending on the latitude, but they cannot be made on cloudy days. The infrared data tell us how the soil water content is spatially divided within the coarser SWC 1000 m product and thus can accurately tell us which fields are relatively wet or dry, compared to the environment. However, the lower temporal resolution of the infrared data can cause the correlation coefficient to drop compared to the SWC 1000 m product. The enhanced-resolution product does get updated every time a new passive microwave observation comes in, but the temporal changes that result from the infrequent infrared observations can cause a degradation in the correlation.
Therefore, when a customer is interested mostly in the temporal changes, often the 1000 m products are the best choice. When they are interested in the spatial variations, the enhanced-resolution product can tell which areas are relatively dry or wet, compared to the environment.
Soil Water Content 20 m
Product Specifications
Table 6: SWC 20 m product specification
| Data Resource | SWC 20 m |
|---|---|
| Source ID | SWC-field_V1.0_20 |
| Satellites Used | AMSR-2, AMSR-E, SMAP, Sentinel-2 |
| Band | L, C and X-band |
| Version | 1.0 |
| Unit | m³/m³ |
| Sensing Depth | ~5 cm |
| Pixel Size | 20x20 m |
| Temporal Resolution | 267-364 observations/year |
| Overpass Time | 06:00 local solar time |
| Geographical Coverage | Global |
| Data Availability | 2018-01-01 - Present Data Gaps: 2019-06-19 to 2019-07-24 2022-08-05 to 2022-09-24 2022-11-16 to 2022-11-18 |
Asset Properties
SWC 20 m is field-based: each observation is delivered as a single-band asset with metadata embedded in the GeoTIFF.
Table 7: Asset properties of SWC 20 m data resources
| Asset Name | Band Name | Unit | Type | Typical Range | No Data Value | Scale | Format |
|---|---|---|---|---|---|---|---|
| swc | Band 1 | m3/m3 | UINT16 | 0 - 1 | 65535 | 0.001 | GeoTIFF |
Input Data
Table 8: List of inputs for SWC 20 m production
| Product | Description |
|---|---|
| Brightness Temperature L band | Soil Moisture Active Passive (SMAP) Level-1B Radiometer Half-Orbit Time-Ordered L band Brightness Temperatures, Version 5 (downloaded from NSIDC in HDF5 format). This Level-1B product provides calibrated estimates of time-ordered geolocated brightness temperatures at 1.41 GHz with a footprint size of 39x47 km. SMAP L band brightness temperatures are referenced to the Earth's surface with undesired and erroneous radiometric sources removed. Data has been available since April 2015 with a latency of 12 hours. Detailed information is available here. |
| Brightness Temperature X band | Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and Advanced Microwave Scanning Radiometer 2 (AMSR-2) Level-1B Radiometer X band Brightness Temperatures (downloaded from JAXA G-portal in HDF5 format). This Level-1B product provides calibrated estimates of geolocated brightness temperatures at 10.7 GHz with a footprint size of 24x42 km. Data has been available from July 2002 to October 2011 (AMSR-E) and from June 2012 (AMSR-2) up to now with a latency of 12 hours. Detailed information is available here |
| Brightness Temperature C band | AMSR-E and AMSR-2 Level-1B Radiometer C band Brightness Temperatures (downloaded from JAXA G-portal in HDF5 format). This Level-1B product provides calibrated estimates of geolocated brightness temperatures at 6.9 GHz with a footprint size of 35x62 km. Data has been available from July 2002 to October 2011 (AMSR-E) and from June 2012 (AMSR-2) up to now with a latency of 12 hours. Detailed information is available here. |
| Brightness Temperature Ka band | AMSR-E and AMSR-2 Level-1B Radiometer Ka band Brightness Temperatures (downloaded from JAXA G-portal in HDF5 format). This Level-1B product provides calibrated estimates of geolocated brightness temperatures at 36.5 GHz with a footprint size of 7x12 km. Data has been available from July 2002 to October 2011 (AMSR-E) and from June 2012 (AMSR-2) up to now with a latency of 12 hours. Detailed information is available here. |
| Brightness Temperature W band | AMSR-E and AMSR-2 Level-1B Radiometer W band Brightness Temperatures (downloaded from JAXA G-portal in HDF5 format). This Level-1B product provides calibrated estimates of geolocated brightness temperatures at 89 GHz with a footprint size of 3x5 km. Data has been available from July 2002 to October 2011 (AMSR-E) and from June 2012 (AMSR-2) up to now with a latency of 12 hours. Detailed information is available here. |
| Reflectances SWIR and NIR | Sentinel-2 Level-2A reflectance data for two bands: SWIR (shortwave infrared around 1610 nm) and NIR (near infrared around 842 nm). |
| Digital Elevation Model | Digital elevation model (DEM) static map resampled at 100 m based on the Copernicus DEM GLO-90 product covering the full global landmass of the time frame of data acquisition (2011-2015). Detailed information is available in the link. |
| Land Cover Map | Custom global land classification including permanent water bodies based on the Copernicus Global Surface Water Bodies product from PROBA-V. Detailed information is available here |
| Soil Map | Soil property maps resampled at 100 m based on the SoilGrids product. SoilGrids was funded by the core funding of ISRIC with additional support from the EUH2020 CIRCASA project. Detailed information is available here, |
Metadata
Metadata embedded in the GeoTIFF contains information about the quality of the observation. For example:
Table 9: Metadata fields of SWC 20 m data resources
| Field | Type | Description | Example |
|---|---|---|---|
PRODUCT_VERSION | String | Version identifier for the product specification | v1 |
SOFTWARE_VERSION | String | Version of the fbsl software that generated the output | 0.4.1 |
INPUT_ASSETS | String | Comma-separated list of input data sources used | NDSWIR_STATS,NDSWIR_RASTER,KA_V_DESC_STATS |
LAST_NDSWIR_DATE | String (ISO date) | Date of the last NDSWIR (Sentinel-2) observation with full coverage | 2024-01-19 |
LAST_NDSWIR_COV | String (fraction) | Coverage fraction of the last NDSWIR observation used | 0.85 (= 85% coverage) |
QUALITY | String | Overall quality assessment: HIGH if valid coverage > 80%, otherwise LOW | HIGH or LOW |
FUSION | String | Whether L-band fusion was applied | YES or NO |
DIVERGENCE_COV | String (fraction) | Fraction of pixels where LPRM algorithm did not converge | 0.05 (= 5% divergence) |
QA_MDPI_LT_0_0001 | String (fraction) | Fraction of pixels with Modified Dual Polarization Index < 0.0001 | 0.12 (= 12% of pixels) |
QA_NO_COVERAGE | String (fraction) | Fraction of pixels with no microwave coverage | 0.0 (= 0% missing) |
QA_FREEZING | String (fraction) | Fraction of pixels flagged as freezing conditions | 0.0 (= 0% frozen) |