CONCLUSION

The findings show that the accuracy of the automatic vectorization and morphometric characterization of drainage networks is influenced by various factors. The DEM that produced the most consistent results was the ALOS-PALSAR DEM. This shows that, when comparing DEMs generated using similar methodologies, the higher the spatial resolution of the DEM, the better the accuracy. Moreover, the DEMs obtained by active radar signal imaging showed better accuracy in relation to the ASTER-GDEM, generated from stereoscopic pairs of optical images created from passive satellite sensors.

The level of detail obtained by automatic vectorization can be brought closer to that of manual vectorization by adjusting the value inputted into the Threshold field of the Channel network and drainage basin tool, reducing variations between the model and the on-ground hydrographic network.

Manual vectorization is the best, or probably the only, option for following circumstance: studies that demand a high level of accuracy; mapping of small watersheds or subwatersheds with few watercourses; and the production of administrative and criminal technical case reports, where accuracy may be called into question and inaccuracy may lead to the incorrect application of the law, for example by calculating a lower number of watercourses and area of permanent preservation areas.

Finally, the consistency of morphometric data can be improved by performing manual vectorization of the drainage divide and watershed perimeter after automatic vectorization, thus increasing accuracy in relation to reality on the ground. Similarly, manual vectorization of the main river improves the accuracy of the parameters related to this variable.