# GOSAT_FTS_L2_CH4_TC

## Variables

The table below lists the variables that are present in the HARP product that results from an ingestion of `GOSAT_FTS_L2_CH4_TC` data.

field name | type | dimensions | unit | description
--- | --- | --- | --- | ---
datetime | double | {time} | [seconds since 2000-01-01] | time of the measurement at end of integration time
longitude | double | {time} | [degree_east] | longitude of the measurement
latitude | double | {time} | [degree_north] | latitude of the measurement
longitude_bounds | double | {time, 4} | [degree_east] | corner longitudes for the geospatial footprint of the measurement
latitude_bounds | double | {time, 4} | [degree_north] | corner latitudes for the geospatial footprint of the measurement
solar_azimuth_angle | double | {time} | [degree] | solar azimuth angle at the observation point
solar_zenith_angle | double | {time} | [degree] | solar zenith angle at the observation point
sensor_azimuth_angle | double | {time} | [degree] | sensor azimuth angle at the surface
sensor_zenith_angle | double | {time} | [degree] | sensor zenith angle at the observation point
CH4_column_number_density | double | {time} | [molec/cm^2] | CH4 column number density
CH4_column_number_density_uncertainty | double | {time} | [molec/cm^2] | uncertainty of the CH4 column number density
index | int32 | {time} |  | zero-based index of the sample within the source product

## Mapping description

The table below details where and how each variable was retrieved from the input product.

field name | mapping description
--- | ---
datetime | path | /scanAttribute/time[]
longitude | path | /Data/geolocation/longitude[]
latitude | path | /Data/geolocation/latitude[]
longitude_bounds | path | /Data/geolocation/footPrintLongitude
description | the corners are calculated by defining a bounding box around the circular footprint area
latitude_bounds | path | /Data/geolocation/footPrintLatitude
description | the corners are calculated by defining a bounding box around the circular footprint area
solar_azimuth_angle | path | /Data/geolocation/solarAzimuth[]
solar_zenith_angle | path | /Data/geolocation/solarZenith[]
sensor_azimuth_angle | path | /Data/geolocation/satelliteAzimuth[]
sensor_zenith_angle | path | /Data/geolocation/satelliteZenith[]
CH4_column_number_density | path | /Data/totalColumn/CH4TotalColumn
CH4_column_number_density_uncertainty | path | /Data/totalColumn/CH4TotalColumnSmoothingError, /Data/totalColumn/CH4TotalColumnRetrievalNoise, /Data/totalColumn/CH4TotalColumnInterferenceError, /Data/totalColumn/CH4TotalColumnExternalNoise
description | the uncertainty returned is the sum of all four error components