# Use of SAR and Optical Time Series for Tropical Forest Disturbance Mapping
## 2 Material and Methods  
### Test Sites  
The study is performed at two test sites in humid tropical forest regions: one test site is located in Peru, near the city of Yurimaguas, and the second test site is located in Gabon, near the city of Fougamou.  
The Peruvian test site (see Figure 1) covers approximately 6000 km\({}^{2}\) around the city of Yurimaguas (76\({}^{\circ}\)05\({}^{\prime}\)W, 5\({}^{\circ}\)45\({}^{\prime}\)S), which is located at the river Huallaga near the border between the Loreto and San Martin regions. It is the same test site that was previously used to demonstrate the SAR shadow method for forest disturbance detection [47]. Most of the study area lies within the tropical rainforest zone, which is characterized by a mean temperature of all months higher than 18 \({}^{\circ}\)C, an annual precipitation of at least 1500 mm, and at most three dry months during winter. In Yurimaguas, the mean long-term temperature is 26 \({}^{\circ}\)C and the mean annual rainfall is 2200 mm [61; 62]. Only in June, July, August, and September the mean monthly rainfall is lower than 200 mm [61]. The Peruvian test site is intensively used and characterized by shifting cultivation, plantations, and mining activities. The patterns of forest degradation strongly differ in extent and temporal behavior. Areas with traditional subsistence farming based on shifting cultivation typically show forest disturbances smaller than 0.5 ha, which by FAO definition is forest degradation [63]. The forests in the area are partly primary and mostly secondary forests, i.e., previously disturbed forests. Forest/Non-forest maps that follow the FAO forest definition [63] and forest disturbance maps are derived for the entire test site. Due to limited availability of reference data, the validation was performed at a small subset of 88.33 km\({}^{2}\), which includes the major forest change drivers and is mainly characterized by areas of shifting cultivation and by forest disturbances that are smaller than 0.5 ha in size.  
The Gabonese study area (see Figure 2) is approximately 6480 km\({}^{2}\) large and it extends over parts of the provinces of Ngouine, Ogooue-Maritime and Moyen-Ogooue. It completely lies within the ecological zone of tropical rainforests. In Fougamou (10\({}^{\circ}\)35\({}^{\prime}\)E, 1\({}^{\circ}\)13\({}^{\prime}\)S), the largest city in the study area, the climatic conditions are very similar to Yurimaguas with a mean long-term temperature of 26 \({}^{\circ}\)C and a mean annual precipitation of 1995 mm with the dry season between June and September, where precipitation does not exceed 100 mm ([[https://de.climate-data.org/location/32332/#climate-graph](https://de.climate-data.org/location/32332/#climate-graph)]([https://de.climate-data.org/location/32332/#climate-graph](https://de.climate-data.org/location/32332/#climate-graph))). The presence of cloud cover in Gabon is nearly continuous throughout the year. The main drivers for deforestation at the test site are (i) mining activities in the north; (ii) large palm oil plantations in the south; and (iii) agricultural activities along roads and rivers. The main driver for forest degradation is industrial selective logging [64], which occurs in several concession areas and is characterized by a large number of very small forest disturbances (<0.2 ha) and related logging roads [65].