Geovariances: Where no one has gone before

 Air pollution mapping

The geostatistical mapping algorithm, called kriging, is based on the specific spatial behavior of the phenomenon via a spatial correlation function calculated from the sample measurements. Because this correlation function determines the shape of the final map, the geostatistical algorithm adapts itself directly to the spatial characteristics of the data, thus eliminating the need for a subjective evaluation.

Whatever the scale, map quality is enhanced by the integration of additional information (meteorology, topography, soil occupation, traffic density, industrial emissions, meteorological and pollution forecast models). Auxiliary information can easily be integrated in the final map by integrating any relationship (linear or non-linear) with the main measures into the kriging algorithm.

We have experience in:

Cartography of NO2

• Accurate mapping of nitrogen dioxide, ozone, benzene particulate matter PM10 taking into account the heterogeneous nature of the data (rural, traffic, industrial and urban stations);
• Air quality mapping in urban areas integrating background and proximity pollution based on pollutant measurements and a physico-chemical road model;
• Real-time mapping of air pollutants through batch procedures aiming at public information (see the websites www.airparif.asso.fr, www.airnormand.asso.fr, www.atmonet.org).

 Monitoring network or sampling campaigns optimization

Because of the probabilistic framework of geostatistics, the variance of the interpolation error can be calculated. This estimation variance only depends on the variogram and the data configuration. Therefore, it is possible to tune additional sample locations to reduce the uncertainty in under-sampled areas.

Probability map NO2>40µg

 Risk analysis and population exposure

The geostatistical simulations allow to compute equally probable images of the reality which are used to assess the variability of the phenomenon and to perform accurate uncertainty quantification.

Public health is your issue. Geovariances consultants provide accurate and reliable solutions to evaluate the probability of human exposure to air pollution:

• Probability of exceeding a pollutant threshold over a given period (day, week, year)
• Probability distribution of the number of inhabitants exposed to a pollution above regulatory limits.