The recognition of the remnants of the Royal Road of the interior land using high-resolution multispectral satellite images

Abstract

The Spaniards built the Royal Road of the Interior Land in the colonial times of Mexico. Such a road ranged between Mexico City and Santa Fe, New Mexico, USA. Some remnants still survive in Mexico, but their geographic location, position, length and condition are not well known. By means of fieldwork and a search of historic records left by the Spaniards, three segments of the Royal Road were identified. Three high-resolution multispectral images from the Pleiades satellite were acquired. Such images cover three zones where the Royal Road segments were located, and fieldwork was carried out. Due to degradation, the segments of the Royal Road show a low contrast with respect to the surroundings but a distinctive texture. A procedure of enhancement and sharpening was applied to the images based on the Vector Laplacian operator and Principal Component Analysis (PCA). Such a procedure enhances the texture and the edges of the Royal Road segments. An RGB false color composite formed by the Laplacian operator, the first principal component, and band 4, produced an image where the Royal Road segments are clearly observed. By means of fieldwork, the geographic coordinates and condition of the Royal Road segments were identified.