I found a count for a street or mall that differs from Targomo's. What can be possible reasons?

Typically footfall/visitor counts that are publicly available are measured in one of the following ways:

• Laser scanners in streets or inside malls. One should expect these to be relatively close to Targomo figures but not match exactly. Notable differences are that we count pedestrians only one time per day, whereas laser scanners can not differentiate unique visitors. Laser counts in streets are also very sensitive to the position of the sensor which does not necessarily coincide exactly with our grid cells.
• Manual street counts. These are typically done on specific days during a fixed time window. Our data is an average over the whole year, across different seasons and weather conditions. A yearly average can differ quite significantly from a daily snapshot.
• GPS data from other providers. Depending on the sophistication of the used algorithms and quality of the source data results can differ quite substantially. We have benchmarked our data against ground-truth measurements from laser scanners across a wide range of countries and we have found our data to be highly accurate and reliable.