Field survey

A handheld Global Positioning System (GPS) receiver (Garmin eTrex 20 X) was used to collect coordinates for each of the two target street trees (J. mimosifolia and P. × acerifolia) and other associated vegetation types from 22 to 24 November 2017 to ground-truth the SPOT 6 satellite data. A total of 711 GPS points was collected from random street trees by visiting most of the major parks and suburbs across the study area (65 732.67 ha) and the distribution of the GPS points collected is indicated in Fig. 2. The study area was divided into suburbs and GPS points were taken selectively from every 100–200 m in the parks or by moving randomly left and right sides of the streets.

The distribution of the ground-truthing GPS points collected for mapping the distribution of two street trees, Jacaranda mimosifolia and Platanus × acerifolia (London Plane) and other land cover classes in the study area, the city of Johannesburg, South Africa, which includes the central business district (CBD), Randburg, Sandton, Houghton, Selby, Crown, and Fairland regions of the city as well as over half of the Alexandra township among others. The map was generated using the ArcGIS desktop software version 10.3 from SPOT 6 image obtained from the South African National Space Agency (SANSA).