| Title Scanning and Digitizing Maps of the Presidial District of San Diego: Locating the boundaries for Distrito de San Diego | |
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Author Jill Bradeen American River College, Geography 350: Data Acquisition in GIS; Fall 2005 Contact Information: jillbradeen@yahoo.com | |
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Abstract This project attempts to map the district boundaries of the historic Presidio of San Diego. Several old maps of the area were scanned and georeferenced, and the boundaries and place names were then digitized using ArcMap. These maps were hard to come by and, individually, they did not cover the entire area. They did, however, overlap and give a good idea of where the boundary was. | |
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Introduction I am currently working on an archaeological report of Old Town San Diego (OTSD) for the California State Department of Parks and Recreation. Recently, my supervisor asked me to use GIS on this project to create a map in ArcMap, displaying the boundaries for the Presidial District of San Diego. He wanted me to align two maps he had of southern California and northern Mexico. He also gave me scanned copies of several other old maps of the area to work with. I decided to georeference and digitize these scanned documents, as I had just learned how to do this in class a few days prior to getting this work assignment. With this process, I hope to display the boundaries of the historic Presidio, plot historic places, and relevant natural resources (water bodies, mountains, etc.) of the time. | |
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Background Between 1769, when it was formally founded, and 1776, the San Diego Presidio (a fort until it was legally established as a presidio in 1774) was the base of operations for expeditions that explored new routes and founded new missions and presidios; and from 1776 until 1837 it continued to be the seat of military jurisdiction in southern California (www.cr.nps.gov). The Presidio was abandoned in 1837 after San Diego became a pueblo (http://ceres.ca.gov). The two scanned maps I aligned for my boss came out of The California diary of Faxon Dean Atherton, 1836-1839 (Doyce B. Nunis, Jr., ed.). They were initially from the same map, but were treated separately in this book, even having different scale bars. These maps were used to name and georeference locations for missions and other places of importance during Presidial times. The other two maps came out of The Dominican Mission Frontier of Lower California (Peveril Meigs, 3D). These maps were used to locate the Presidial District boundaries. One of these maps shows the location of the northern Presidial boundary and most of its eastern boundary. The other map shows the location of the southern boundary for the Dominican missions, which was probably the same as the southern Presidial boundary. Fortunately, the Pacific coast defines the western boundary, so I am fairly certain of its accuracy. Spatial data came from: ESRI_Data\mexico\drainage.shp ESRI_Data\mexico\states.shp ESRI_Data\Elev\northamerica CA State Parks Layer Control: Lakes from Base.HYDRO.MjrWtrBdys CA State Parks Layer Control: Cities from Base.CARTOG.Cities CA State Parks Layer Control: California from Base.BDYS.California | |
Alta California  |
Baja California Norte 
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| The maps above are both from Nunis
(1964) and are the original two I aligned for my boss. The one on the left
shows southern California and the one on the right shows nothern Mexico. I used
these maps for georeferencing places of importance during Presidial times. | |
Northern Presidial District Boundary  |
Probable Southern Presidial District
Boundary
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| The maps above are both from Meigs (1935)
and were used to locate the Presidial District boundaries. | |
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Methods Datasets from the California State Parks network were used, as were datasets from ESRI. I used the following process to create a map of the Presidial District boundaries: 1) I received scanned maps from my boss. 2) I created a base map in ArcMap using datasets of California and Mexico, projecting them into NAD83. I also brought in city points and water bodies to help myself georeference the scanned maps. 3) I georeferenced the scanned maps. 4) I digitized place names and boundaries. | |
The map to the right shows the two Nunis (1964) maps aligned. As they originate from the same historic map, they lined up very well and were easy to georeference. |
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| The maps above show the
Meigs (1935) maps georeferenced. The Northern Presidial District
Boundary map, on the left, was very difficult to georeference. I was
only able to georeference two points along the coast. All additional
points stretched the image quite severely. Also, the geography of the
coastline does not match that of my base map.
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The map to the right simply shows how all of the maps overlay. |
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Results | |
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I created the map to the left in ArcMap. This map shows the digitized locations of missions, the presidio, and other places relevant to the time that the San Diego Presidio District was operational. |
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Analysis I was fairly successful in producing a map of the boundaries for the Presidial District of San Diego. The map used to create the northern boundary was difficult to georeference, so this boundary was estimated as closely as possible. The southern boundary is based on mission boundaries and probably represents the Presidial District boundary fairly accurately. The Pacific Coast defines the western boundary, but the eastern boundary had to be estimated. The eastern boundary was created from the same map as the northern boundary, but was not complete at the southern end. | |
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Conclusions I ran into quite a few problems with this project. First of all, several of the scanned maps I used were difficult to georeference. With better maps, the boundaries I created might be more accurate. Also, this was initially a work project and some of the data layers I was using were only available through a network connection. This leads me to yet another problem. After I had aligned the maps that my boss wanted, he decided to just use the Northern Presidial District Boundary map (Meigs, 1935) for this report and did not need me to make a map anymore. This made it difficult for me to complete this school project at work, and without remote access to the network I could not work on it at school. The problems I encountered, with the exception of georeferencing, were more annoying than anything and did not affect the outcome of this project. | |
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References Meigs, 3D., Peveril, 1935.The Dominican Mission Frontier Of Lower California. , University of California Press, Berkeley, CA. Nunis, Jr., Doyce B. ed., 1964.The California diary of Faxon Dean Atherton, 1836-1839. San Francisco: California Historical Society, 1964. | |