Cartographic Accuracy Standard (CAS) of the digital terrain model of the digital and continuous cartographic base of the state of Amapá: case study in the city of Macapá

Abstract

The Cartographic Accuracy Standard (CAS) is a quality parameter used by the Brazilian standard to estimate the positional quality of cartographic products in their degree of precision, also including altimetry. The Digital and Continuous Cartographic Base of Amapá -BCDCA has a large amount of freely available spatial information, for the study of its territory within the state of Amapá. This project, a partnership between the Government of the State of Amapá and the Directorate of Geographical Services of the Brazilian Army (DSG), obtained a large amount of SAR data by interferometry. Among the resulting products, the Digital Terrain Model -DTM has a wide range of applications: watershed analysis, infrastructure program, diagnosis of environmental risks and so many others. Therefore, the present work aims to evaluate the altimetric data (DTM) provided by the BCDCA through 2172 orthometric points calculated from the Brazilian Network for Continuous Monitoring -RBMC measured in the field in the city of Macapá, capital of the State of Amapá. For the level curves, the results presented class A for the 1: 10 000 scale, at an equidistance of 5 m, showing that the DTM product is highly reliable for urban applications.

Challenges of relief modeling in flat areas: a case study in the Amazon coast floodplains

“…For the main global DEMs, several studies in Brazil indicate that their vertical accuracy is lower in the Amazon region than in other parts of the country, where the vegetation cover is smaller and altimetric amplitude is higher (Miceli et al 2011;Grohmann 2018;Orlandi et al 2019;Santos Filho et al 2022). The main limitations of these models in forested areas are the fact that they are generated by short wavelength radar (i.e., X-band and C-band), where the radar signal is not capable of reaching the ground and the radar phase is decorrelated by the foliage movement between two acquisitions in repeat pass interferometry (Polidori et al 2018).…”

“…BCDCA DTM and BCDCA DSM, that originally have a 2.5 m grid, can be used as examples, since even on a 30 m mesh, BCDCA DSM showed much more roughness in the visual comparison results than the other DSMs, which indicates that on the 2.5 m mesh this would be aggravated. Nevertheless, the use of Lidar and high-resolution DTMs (such as the BCDCA DTM 2.5 m mesh) are more suitable for representing floodplains at larger scales, since the canopy effect is attenuated (Colby and Dobson 2010;Clubb et al 2017;Santos Filho et al 2022;Bielski et al 2024). This effect confirms the importance of not only specifying the DEM surface (whether a DTM or a DSM) but indicate its scale for a better understand of the limitations and what expect when using it.…”