DAN passive measurements provide better spatial coverage than the active measurements because they can be acquired while the rover is moving.
Alternatively, herbarium data can be used to fit species distribution models and their predictions can be used to provide complete spatial coverage and derive species richness maps.
An alternative approach to validation might include the use of inventory-based NPP datasets where available, which provide complete spatial coverage [105].
A random-sampling method was included in this study as a benchmark because its characteristics are well known and conform to the requirements of sampling theory even though such methods often fail to provide good spatial coverage.
For a better understanding of the global phenomena of ionospheric irregularities, a RO technique using multiple satellites that can provide dense spatial coverage of the world such as FORMOSAT-3/COSMIC (F3/C) is essential.
A sufficient number of density measurements should be performed to: (1) provide ample spatial coverage of each rock unit and (2) to facilitate the calculation of statistics to assess the distribution, range, and standard deviation of density in each rock unit.
Fig. 1 shows that the measured data are sparse, and do not provide complete spatial coverage of the study region.
An alternative approach to validation might include the use of inventory-based NPP datasets where available, which provide complete spatial coverage [ 105].
These data are modelled-PCM yearly mean background concentrations in μgm−3 at a 1 km × 1 km resolution, which hence provide complete spatial coverage across the study area with no missing data.
However, even combining both data sets still does not provide sufficient spatial coverage of NO2 for epidemiological studies, and modelled concentrations on a regular grid from atmospheric dispersion models are also available.
The monitoring data were highly unbalanced, with a small number of locations providing long time series of several years' duration and a larger number of locations providing broader spatial coverage, but at a relatively small number of time points.
