{"id":578,"date":"2022-02-11T13:29:53","date_gmt":"2022-02-11T18:29:53","guid":{"rendered":"https:\/\/pressbooks.library.upei.ca\/geospatialhumanities\/?post_type=chapter&p=578"},"modified":"2023-01-16T19:57:42","modified_gmt":"2023-01-17T00:57:42","slug":"part-iii-b-opening-rasters","status":"publish","type":"chapter","link":"https:\/\/pressbooks.library.upei.ca\/geospatialhumanities\/chapter\/part-iii-b-opening-rasters\/","title":{"raw":"Part III B: Opening Rasters","rendered":"Part III B: Opening Rasters"},"content":{"raw":"Now that we have learned about vector data, we can turn our attention to raster data. A raster is a digital image of a map that has accurate coordinates added to it through the process of georeferencing. This textbook will teach you how to georeference in Chapter 3: Georeferencing. For now, we will use a raster that has already been georeferenced.\r\n\r\nThe raster we will add is a reproduction of the map that British naval captain Samuel Holland produced in the 1760s. Holland produced this map to provide the British, who had just acquired the Island, with a better understanding of PEI (or, as it was known at the time, St. John\u2019s Island). Holland surveyed the Island and divided the Island into 67 lots, which were then given out to British owners in the Great Lottery of 1767. This reproduction of Holland\u2019s original map was produced in 1798.\r\n\r\nMaps like this one show how, at the time, the Island\u2019s forests were so dense that they heavily influenced settlement patterns. Settlers could not easily penetrate the forests, so most of the villages on the map are along the coasts or along the navigable rivers.\r\n\r\nAfter we add the 1798 map, we can compare the settlement locations at that time with the ones from the modern OpenStreetMap basemap. We will be able to see how deforestation\u2014along with other factors, such as the construction of Prince Edward Island Railway in the 1870s\u2014allowed Islanders to settle throughout the Island\u2019s interior. We can see towns in the Island\u2019s interior today, such as Kensington and Hunter River. These towns did not exist in the early settlement period, partly because the dense forest made it difficult to traverse the Island\u2019s interior.\r\n

Adding a Raster<\/h1>\r\nLet\u2019s add the 1798 map to our project.\r\nClick here to download the 1798 map<\/a> to your Data folder.\r\n\r\n[caption id=\"attachment_579\" align=\"aligncenter\" width=\"977\"]\"Figure Figure 1.65<\/strong>[\/caption]\r\n\r\nWe will use this file as the first raster layer we add to our project.\r\n\r\n\u25cf Use the Browser to add the 1798 map raster to QGIS in the same way that you added vector layers.\r\n\r\n[caption id=\"attachment_580\" align=\"aligncenter\" width=\"977\"]\"Figure Figure 1.66.<\/strong>[\/caption]\r\n

Symbolizing the Coastline File over the Top of a Raster<\/h1>\r\nTo get a sense of the coastline on which most Islanders settled before the Island\u2019s interior was deforested, we can move the coastline layer above the PEI_HollandMap1798_compLZW.\r\n