Cartographic memory preservation of the Petrópolis city in Brazil: Koeler map scanning using photographic survey

Abstract

Historical cartographic documents have been increasingly essential to several studies, especially when understanding how the current forms of a landscape are structured. In this regard, these documents, along with the assistance of new digital technologies, are preserved and made available to the public. This research focused on investigating the Koeler Plan, a document providing guidance on urban planning for the development of the city of Petrópolis. The plan’s milestone is the Petrópolis Map (1846), which became known as Koeler Map, in honor of its creator. The map was made at a scale of 1:5,000 and contains different cartographic elements such as hydrography, public parks, streets, blocks, and land reserved for public and religious buildings. This research aims to digitally reproduce this map, since its restoration and further use are quite difficult due to its current conditions. The methodology comprises photographic survey techniques using a high resolution digital camera and a track system which moves the camera vertically and horizontally. Several tests were made using multiple georeferencing algorithms to check which of them would better adjust into a mosaic the 191 photographs taken and preserve the features for the digital map generation. The process was developed in five pairs of photographs distributed along the map area, using ArcGIS 10.1 software with different transformations: Zero Order Polynomial, 1st Order Polynomial (Affine), 2nd Order Polynomial, 3rd Order Polynomial, Adjust, Projective Transformation, and Spline. After georeferencing these pairs, a test was made based on the distortions produced in area and length, in addition to the RMS for each transformation. From these results, it was found that the 1st Order Polynomial (Affine) transformation had lower distortion values for the photographs, which allowed a highest quality photo mosaicking.