Table 1.
Demographic description of 160 participants for which concurrent semi-structured interviews and GPS tracking were performed.
Figure 1.
Locations inferred by (A) semi-structured interviews (SSI) and (B) GPS units.
(A) Spatial distribution of all locations reported as visited by 160 participants during a 14-day period. (B) Raw GPS tracks (yellow points) and locations inferred after the application of a data-reduction algorithm (black dots) that assigns each track to a specific location code in the Iquitos GIS.
Table 2.
Comparison of number of “concordant” locations identified by semi-structured interviews and GPS from both study phases.
Figure 2.
Concordance between SSI locations and raw GPS positions at different distance buffer thresholds, GPS data collection frequencies, and number of GPS points.
Concordance was expressed as the percentage of locations for which a SSI-GPS match was found.
Figure 3.
Concordance between SSI locations and raw GPS positions at 20 meters from a SSI location.
Concordance is expressed as the proportion of locations for which a SSI-GPS match was found. Panels show values for different location types, combinations of GPS data collection frequencies (15, 90 and 150 seconds) and number of GPS points used to define a visit (1, 5 and 10 points).
Figure 4.
Sample map to interview participants about possible causes of discordance between GPS-derived vs. semi-structured interview locations.
Given both types of locations were joined to the Iquitos GIS, the lot code was provided to ease identification of locations in the database. Size of points was proportional to reported or calculated time spent at each location. Inset of map shows locations within the city of Iquitos. GPS-derived locations were obtained using a clustering algorithm.
Table 3.
Reasons for discordance given by participants between locations from semi-structured interviews (SSI) and GPS data, from Phase 2 (n = 101).