Portolan haritaların mapanalyst uygulaması ile planimetrik doğruluk analizi

Abstract

Geçmişten günümüze kadar ki dönem incelendiği zaman haritacılığın temelleri olarak kabul edilebilecek çizimlerin tarih öncesi çağlarda orta çağ dönemine rastladığı kabul edilmektedir. Nehir, dağ, yol gibi bir kaç ayrıntı içeren çizimler mağaralara, kayalara hatta post ve deri gibi taşınabilir eşyaların üzerine çizilmişlerdir. Günümüzde bu kalıntılar, diğer tarihi eserler gibi insanlık için önemli sayılabilecek kültür varlıkları arasında kabul edilmektedir. İnsanlar yerleşim yeri olarak genellikle deniz kıyıları ve suyun bulunduğu bölgeleri tercih etmişlerdir. Bu bölgeler deniz ticaretinin de etkisiyle insanlık için çok önemli merkezler ve daha ötesi devletler haline gelmiştir. Özellikle Akdeniz devletleri, ticaret ve güvenlik nedeniyle kıyı haritaları (Portolan) yaptırmıştır. Bu gelişmeler doğrultusunda haritacılık bir meslek olarak kabul edilmiştir. Haritacılığın gelişmesiyle birlikte bilinmeyen yerlere gidilmesi ve keşifler çağının başlaması sağlanmıştır. Bu noktada geçmiş dönemde hazırlanan ve bir çok gelişmeye neden olan eski kıyı haritalarının doğruluğu günümüz araştırmacılarının ilgisini çekmektedir. Eski kıyı haritalarının yapımında kullanılan yöntemler, planimetrik doğruluk ve üzerinde yer alan bilgilerin doğruluğu gibi konular araştırmalar arasında yer almaktadır. Gelişen teknoloji ve bilgisayar çağı ile birlikte bu araştırmalar artmakta ve yöntemler kolaylaşmaya başlamıştır.Günümüzde bilgisayarların yardımı ile geçmişte yapılması mümkün olmayan analizlerin yapılması mümkün olmaya başlamıştır. Gelişen programlama dilleri vasıtasıyla oluşturulan programlar bir çok ana bilim dalı için araştırmalara ön ayak olmaktadır. Haritacılık için ise geliştirilen bir çok CBS (Coğrafi Bilgi Sistemi) programı bulunmaktadır. Bu programlar vasıtasıyla haritacılıkta bir çok farklı konuda analizler ve değerlendirmeler yapılabilmektedir. Bu çalışmada CBS programlarından biri olan MapAnalyst programı kullanılarak eski dönem kıyı haritalarının analizi yapılmıştır.MapAnalyst programı eski haritaların doğruluk analizi için kullanılabilen ücretsiz ve açık kaynak kodlu bir yazılımdır. MapAnalyst programı sayesinde geçmiş dönemler için çok önemli olan kıyı haritalarının doğruluğu hakkında bilgi sahibi olunabilmektedir. Eski harita ile günümüz teknolojileri ile hazırlanan güncel haritaların eş noktalar vasıtasıyla karşılaştırılması yapılmaktadır. Çalışmada Marmara Deniz'i, Ege Deniz'i, Akdeniz ve Karadeniz'i baz alan eski kıyı haritalarının modern harita ile karşılaştırması yapılarak planimetrik doğruluğu hakkında bilgi sahibi olunması hedeflenmiştir. Uygulamada orta ölçekli haritalar kullanılmıştır. Eski haritalar programa sayısallaştırılarak eklenmiştir. Sonuç olarak MapAnalyst programı ile yapılan analizlerin vektör, deformasyon ağı, eş uzunluk ve eş açı deformasyon eğrileri vasıtasıyla görselleştirilerek anlatımı sağlanmıştır. Görselleştirmeler üzerinden eski haritalardaki hataların gösterimi gerçekleştirilmiştir.

When the period from past to present is examined, it is accepted that the drawings which can be accepted as the foundations of mapping are found in the middle ages in prehistoric times. Drawings with a few details such as river, mountain and roads were drawn on caves, rocks and even portable goods such as post and leather. Today these remains are recognized among the cultural assets and heritage that can be considered important for humanity, like other historical artifacts.People generally settled near coasts and waterfronts. With respect to shipping trade, these regions had became very important centers for humanity and beyond that states. Especially the Mediterranean states have made coastal maps (Portolan) for trade and security. In line with these developments, cartography was accepted as a profession. With the development of cartography, traveling to unknown places, reduction of ship losses, acceptance of cartography as a profession, performing more reliable sea voyages, drawing maps of the unique appearance of the earth, commencing map trading, shortening of expedition times, emerging of cartography and maps in the Ottoman Empire and leading the age of discoveries were provided.Portolan maps were drawn by the sailors and cartographers of the period by taking into account the distance traveled by the compass rose. Produced with a technique suitable for the conditions of the period, portolan maps also have unique features. As well as for the sailor, portolan maps were also produces for the sovereigns of the period.At this point, the accuracy of the old coastal maps attract the attention of today's researchers. The methods used in the construction of the old coastal maps, planimetric accuracy and accuracy of the information are the subjects of many researches. Advancing technologies and information age, lead an increase at these researches and ease the methods.Today, with the lead of computers, it is possible to carry out analyzes that are not possible in the past. The programs created through the developing programming languages lead to research for many branches of science. There are many GIS (Geographical Information System) programs developed for cartography. Through these programs, analyzes and evaluations can be made on many different topics in cartography. In this study, it is aimed to analyze the old coastal maps by using the MapAnalyst program which is one of the GIS programs.MapAnalyst is a free open source software designed for accuracy analysis of old maps. Its main purpose is to create a visualization showing the geometric accuracy and deformations of the old maps. It is a java based program developed by Bernash Jenny, a faculty member at Monash University. In general, Mapanalyst calculates via control points through old and new maps. Via MapAnalyst, the scale, rotation and statistical indicators of the old maps can also be calculated. The program can be downloaded from `http://mapanalyst.org/` with the current version.Through the MapAnalyst program, it is possible to know the accuracy of the coastal maps which are very important for the past periods. The comparison of the old map and the current maps prepared with today's technologies is made by means of the identical points. Previous applications with MapAnalyst were also examined.In this study, 4 different portolan maps drawn by Diego Homem, Battista Agnese, Joan Martines and Jean François Roussin were considered. It is not possible to speak of a modern projection on maps. However, it was determined that compass rose method which is considered as the most important portolan map drawing technique of the period was taken into consideration in the construction of 4 these portolan maps. This method is generally based on the calculation of length by the speed of the ship and the distance traveled, taking into account the compass and wind direction. Small and medium sized maps were used in the application. Old maps were added to the program by digitizing.OpenStreetMaps for Portolan maps are taken as reference and accuracy analyzes are performed via MapAnalyst application. OpenStreetMaps has been referenced due to accuracy and efficiency on small and medium-sized maps. For the planimetric accuracy analysis of the portolan map, the application of the old map was loaded into the system by running the application. In the application, there is the old map in the right part and OpenStretMap reference map in the left part. After the old map loading process is completed, checkpoints are marked by city names that can be determined on both maps. The city names on the old map are Latin or historical names of the region. At this point, the historical names of cities added to Google Earth plugin is used. The approximate position accuracy was kept low because the region names during the assignment of points were taken into account. Control points are assigned to the locations determined between the old map and the current map. Each control point marked on both maps is connected to each other.After these punctuation operations, `compute` tab that is located in the upper left corner of the application, is being runned to start calculation. As a result, the application performs the visualization. With `compute` command, the application can perform 4 different visualizations as decomposition grids, displacement vectors, scale and rotational equivalent curves (isolines).In the MapAnalyst application, firstly the map drawn by Diego Homem in 1574 was taken into consideration for the planimetric accuracy of the portalan maps. Diego Homem (1521 - 1576) is a Portuguese cartographer. 53 point pairs were selected on the maps. This size of this map is 61.5 x 44.4 cm (5242 x 7266 pixels). Diego Homem used the compass rose method on the this map.Secondly, the portolan map of Battista Agnese drawn in 1553 was taken into consideration. Battista Agnese (1500 - 1564) is a cartographer from the Republic of Genoa. 41 point pairs were selected on the maps. The size of this map is 135.1 x 93.2 cm (6385 x 4401 pixels). Battista Agnese used the compass rose method on the this map.Thirdly, the portolan map drawn by Joan Martines in 1578 was taken into consideration. Joan Martines (1556 - 1590) is a cartographer from Mallorca. 58 point pairs were selected on the maps. The size of this map is 63.2 x 98.7 cm (2985 x 4665 pixels). Joan Martines used the compass rose method on the this map.Finally, the portolan map of Jean François Roussin drawn in 1661 was taken into consideration. Jean François Roussin (17th century) is a Marseille cartographer. 62 point pairs were selected on the maps. The size of this map is 138.9 x 184.1 cm (6561 x 8697 pixels). Jean François Roussin used the compass rose method on the this map.As a result of this study, the average scale, mean rotation and mean location error of portolan maps were determined. The data obtained with MapAnalyst application is visualized.Obtained statistical data determined that 4 different portolan maps made in different periods can be useful works considering the time conditions. Although it is not as much as the maps produced with today's technologies, it is thought to be an important resource for the users of these maps in the period. When the compass rose in the center of the maps is taken into consideration, it is determined that the errors increase parallel to the distance from the center. In some parts, it has even been systematically shifted in a certain direction. In addition, as the scale of the map decreases, the amount of deformation increases. As the area expands and the scale increases, the calculated error increases. Although the compass rose method and knot calculation used in the period were not considered as a modern method, it is thought that it transferred the general geography properly or at least partially.The analyzes made with MapAnalyst program were visualized and explained through vector, grid and isolines. The visualization of the errors in the old maps was realized. As a result of the comparison of the maps drawn in the previous period with the maps prepared in the current period, MapAnalyst was found to be a very important guide for commenting on old maps. Statistical data such as spatial vectors, scale, orientation, position error of old maps can be obtained through this application. It was also found that this program was not suitable for the analysis of large areas. It is thought that as a result of the large coverage area and scale of large maps, distortions may increase and accurate calculations and analysis cannot be performed.