Self-organizing cultured neural networks: Image analysis techniques for longitudinal tracking and modeling of the underlying network structure

Esta tesis estudia la evolución estructural de conjuntos de neuronas como la capacidad de auto-organización desde conjuntos de neuronas separadas hasta que forman una red (clusterizada) compleja. Esta tesis contribuye con el diseño e implementación de un algoritmo no supervisado de segmentación basado en grafos con un coste computacional muy bajo. Este algoritmo proporciona de forma automática la estructura completa de la red a partir de imágenes de cultivos neuronales tomadas con microscopios de fase con una resolución muy alta. La estructura de la red es representada mediante un objeto matemático (matriz) cuyos nodos representan a las neuronas o grupos de neuronas y los enlaces son las conexiones reconstruidas entre ellos. Este algoritmo extrae también otras medidas morfológicas importantes que caracterizan a las neuronas y a las neuritas. A diferencia de otros algoritmos hasta el momento, que necesitan de fluorescencia y técnicas inmunocitoquímicas, el algoritmo propuesto permite el estudio longitudinal de forma no invasiva posibilitando el estudio durante la formación de un cultivo. Además, esta tesis, estudia de forma sistemática un grupo de variables topológicas que garantizan la posibilidad de cuantificar e investigar la progresión de las características principales durante el proceso de auto-organización del cultivo. Nuestros resultados muestran la existencia de un estado concreto correspondiente a redes con configuracin small-world y la emergencia de propiedades a micro- y meso-escala de la estructura de la red. Finalmente, identificamos los procesos físicos principales que guían las transformaciones morfológicas de los cultivos y proponemos un modelo de crecimiento de red que reproduce el comportamiento cuantitativamente de las observaciones experimentales. ABSTRACT The thesis analyzes the morphological evolution of assemblies of living neurons, as they self-organize from collections of separated cells into elaborated, clustered, networks. In particular, it contributes with the design and implementation of a graph-based unsupervised segmentation algorithm, having an associated very low computational cost. The processing automatically retrieves the whole network structure from large scale phase-contrast images taken at high resolution throughout the entire life of a cultured neuronal network. The network structure is represented by a mathematical object (a matrix) in which nodes are identified neurons or neurons clusters, and links are the reconstructed connections between them. The algorithm is also able to extract any other relevant morphological information characterizing neurons and neurites. More importantly, and at variance with other segmentation methods that require fluorescence imaging from immunocyto- chemistry techniques, our measures are non invasive and entitle us to carry out a fully longitudinal analysis during the maturation of a single culture. In turn, a systematic statistical analysis of a group of topological observables grants us the possibility of quantifying and tracking the progression of the main networks characteristics during the self-organization process of the culture. Our results point to the existence of a particular state corresponding to a small-world network configuration, in which several relevant graphs micro- and meso-scale properties emerge. Finally, we identify the main physical processes taking place during the cultures morphological transformations, and embed them into a simplified growth model that quantitatively reproduces the overall set of experimental observations.

Self-organizing cultured neural networks: Image analysis techniques for longitudinal tracking and modeling of the underlying network structure (versión actualizada)

Esta tesis estudia la evolución estructural de conjuntos de neuronas como la capacidad de auto-organización desde conjuntos de neuronas separadas hasta que forman una red (clusterizada) compleja. Esta tesis contribuye con el diseño e implementación de un algoritmo no supervisado de segmentación basado en grafos con un coste computacional muy bajo. Este algoritmo proporciona de forma automática la estructura completa de la red a partir de imágenes de cultivos neuronales tomadas con microscopios de fase con una resolución muy alta. La estructura de la red es representada mediante un objeto matemático (matriz) cuyos nodos representan a las neuronas o grupos de neuronas y los enlaces son las conexiones reconstruidas entre ellos. Este algoritmo extrae también otras medidas morfológicas importantes que caracterizan a las neuronas y a las neuritas. A diferencia de otros algoritmos hasta el momento, que necesitan de fluorescencia y técnicas inmunocitoquímicas, el algoritmo propuesto permite el estudio longitudinal de forma no invasiva posibilitando el estudio durante la formación de un cultivo. Además, esta tesis, estudia de forma sistemática un grupo de variables topológicas que garantizan la posibilidad de cuantificar e investigar la progresión de las características principales durante el proceso de auto-organización del cultivo. Nuestros resultados muestran la existencia de un estado concreto correspondiente a redes con configuracin small-world y la emergencia de propiedades a micro- y meso-escala de la estructura de la red. Finalmente, identificamos los procesos físicos principales que guían las transformaciones morfológicas de los cultivos y proponemos un modelo de crecimiento de red que reproduce el comportamiento cuantitativamente de las observaciones experimentales. ABSTRACT The thesis analyzes the morphological evolution of assemblies of living neurons, as they self-organize from collections of separated cells into elaborated, clustered, networks. In particular, it contributes with the design and implementation of a graph-based unsupervised segmentation algorithm, having an associated very low computational cost. The processing automatically retrieves the whole network structure from large scale phase-contrast images taken at high resolution throughout the entire life of a cultured neuronal network. The network structure is represented by a mathematical object (a matrix) in which nodes are identified neurons or neurons clusters, and links are the reconstructed connections between them. The algorithm is also able to extract any other relevant morphological information characterizing neurons and neurites. More importantly, and at variance with other segmentation methods that require fluorescence imaging from immunocyto- chemistry techniques, our measures are non invasive and entitle us to carry out a fully longitudinal analysis during the maturation of a single culture. In turn, a systematic statistical analysis of a group of topological observables grants us the possibility of quantifying and tracking the progression of the main networks characteristics during the self-organization process of the culture. Our results point to the existence of a particular state corresponding to a small-world network configuration, in which several relevant graphs micro- and meso-scale properties emerge. Finally, we identify the main physical processes taking place during the cultures morphological transformations, and embed them into a simplified growth model that quantitatively reproduces the overall set of experimental observations.

World Bathymetric Chart of the Oceans, 1899 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Bathymetrical chart of the oceans, showing the "deeps" according to Sir John Murray. It was published by the Royal Geographical Society in 1899. Scale [ca. 1:100,000,000]. The image inside the map neatline is georeferenced to the surface of the earth and fit to the 'World Gall Stereographic' projection with the central meridian at 20.00000 degrees west. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, shoreline features, and more. Relief shown by hypsometric tints. Depths shown by gradient tints. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Atmospheric Temperature Isotherms (January), 1884 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Karte der Januar-Isotherme. It is part of a two map set: [Karten der Isothermen, von Alexander Supan]. It was published by Ed. Holzel in 1884. Scale [ca. 1:110,000,000]. Map in German. The image inside the map neatline is georeferenced to the surface of the earth and fit to a non-standard 'Mercator' projection with the central meridian at 17.666 degrees west. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, selected cities, shoreline features, and more. Isotherms are shown at 2 degree intervals for January. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Atmospheric Temperature Isotherms (July), 1884 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Karte der Juli-Isothermen. It is part of a two map set: [Karten der Isothermen, von Alexander Supan]. It was published by Ed. Holzel in 1884. Scale [ca. 1:110,000,000]. Map in German. The image inside the map neatline is georeferenced to the surface of the earth and fit to a non-standard 'Mercator' projection with the central meridian at 17.666 degrees west. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, selected cities, shoreline features, and more. Isotherms are shown at 2 degree intervals for July. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map Showing Geomagnetic Meridians and Parallels, 1849 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Wachsende Karte der Magnetischen Meridiane und Parallelen : Gegründet auf die Beobachtungen der Declination welche sämmtlich auf das Jahr 1825 reducirt worden sind, von dem Schiffs Kapitain L. I. Duperrey. It was published by Stablstich (diretion v. Kleinecht) aus der Schweinfurter Geographischen Graviranstalt de Bibliographischen Instituts in [1849]. Scale [ca. 1:190,000,000]. Map in German. The image inside the map neatline is georeferenced to the surface of the earth and fit to a non-standard 'Mercator' projection with the central meridian at 180 degrees west. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as geomagnetic meridians, parallels, and magnetic declination, selected cities and other human settlements, shoreline features, and more. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map, 1725 (Image 1 of 2) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Carte generale de toutes les costes du Monde : et les pays nouvellement decouvert, dressé sur les relations les plus nouvelles et principalement sur le carte que Monsieur N. Witsen à donnée au public. It was published by Iean Cóvens et Corneille Mortier Libraires in [1725]. Scale [ca. 1:450,000]. This layer is image 1 of 2 total images of the two sheet source map representing the western portion of the map. Text in French. The image inside the map neatline is georeferenced to the surface of the earth and fit to the 'World Mercator' projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, cities and other human settlements, territorial boundaries, shoreline features, and more. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map Showing Isodynamic Lines, 1849 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Darstellung der isodynamischen Linien : nach den Beobachtungen der magnetischen Intensität, die in den Jahren 1790 bis 1830 gemacht worden sind, Namen der Beobachter: De Rossel, A. v. Humboldt, Sabine, Hansteen, Duperrey, Keilhau u. Boeck, Keilhau, Litke, King, Due, Erman, Kupffer. Die vorlieg. Darstellung ist von Duperry, Kapitain der französ. Marine, entworfen. It was published by [Stablstich (diretion v. Kleinecht) aus der Schweinfurter Geographischen Graviranstalt de Bibliographischen Instituts] in [1849]. Scale [ca. 1:190,000,000]. The image inside the map neatline is georeferenced to the surface of the earth and fit to a non-standard 'Mercator' projection with the central meridian at 180 degrees west. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as geomagnetic isodynamic lines, selected cities and other human settlements, shoreline features, and more. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map, ca. 1774 (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: An accurate chart of the world with the new discoveries : also a view of the general &c coasting trade winds, monsoons or shifting trade winds & the variations of the compass ; from the latest and best authorities by T. Kitchin, Geographer for the Lond. Mag. It was published ca. 1774. Scale [ca. 1:90,000,000]. The image inside the map neatline is georeferenced to the surface of the earth and fit to the 'World Mercator' projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, cities and other human settlements, trade winds, magnetic variations, shoreline features, and more. Relief shown pictorially. Includes text and notes. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map Showing Routes of Exploration and Discovery, 1790 (Image 1 of 8) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Chart of the world on Mercators projection : exhibiting all the new discoveries to the present time, with the tracks of the most distinguished navigators since the year 1700 carefully collected from the best charts, maps, voyages, &c. extant and regulated from the accurate astronomical observations made in three voyages performed under the command of Captn. James Cook in the years 1768, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 & 80, compiled and published by A. Arrowsmith, geographer; by permission of Simon McTavish Esq[r] is correctly delineated the discoveries of Mr. McKenzie laid down from his original journal in the year 1789. It was published by A. Arrowsmith, April 1, 1790. Scale [ca. 1:20,000,000]. This layer is image 1 of 8 total images of the seven sheet source map. Covers portions of eastern Asia, Siberia, Russia, Pacific Islands, and western portions of Canada and the United States including Alaska. The image inside the map neatline is georeferenced to the surface of the earth and fit to a non-standard 'World Mercator' projection, with the central meridian at 180 degrees west. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. Note: The central meridian of this map is not the same as the Prime Meridian and may wrap the International Date Line or overlap itself when displayed in GIS software. This map shows features such as drainage, cities and other human settlements, territorial boundaries, shoreline features, and more. Relief shown by hachures. Depths shown by soundings. Includes routes, locations, and dates of James Cook's voyages. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map Showing Routes of Exploration and Discovery, 1790 (Image 2 of 8) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Chart of the world on Mercators projection : exhibiting all the new discoveries to the present time, with the tracks of the most distinguished navigators since the year 1700 carefully collected from the best charts, maps, voyages, &c. extant and regulated from the accurate astronomical observations made in three voyages performed under the command of Captn. James Cook in the years 1768, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 & 80, compiled and published by A. Arrowsmith, geographer; by permission of Simon McTavish Esq[r] is correctly delineated the discoveries of Mr. McKenzie laid down from his original journal in the year 1789. It was published by A. Arrowsmith, April 1, 1790. Scale [ca. 1:20,000,000]. This layer is image 2 of 8 total images of the seven sheet source map. Covers portions of Europe, Northern Africa, and Asia. The image inside the map neatline is georeferenced to the surface of the earth and fit to the 'World Mercator' projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, cities and other human settlements, territorial boundaries, shoreline features, and more. Relief shown by hachures. Depths shown by soundings. Includes routes, locations, and dates of James Cook's voyages. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map Showing Routes of Exploration and Discovery, 1790 (Image 3 of 8) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Chart of the world on Mercators projection : exhibiting all the new discoveries to the present time, with the tracks of the most distinguished navigators since the year 1700 carefully collected from the best charts, maps, voyages, &c. extant and regulated from the accurate astronomical observations made in three voyages performed under the command of Captn. James Cook in the years 1768, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 & 80, compiled and published by A. Arrowsmith, geographer; by permission of Simon McTavish Esq[r] is correctly delineated the discoveries of Mr. McKenzie laid down from his original journal in the year 1789. It was published by A. Arrowsmith, April 1, 1790. Scale [ca. 1:20,000,000]. This layer is image 3 of 8 total images of the seven sheet source map. Covers portions of South America, the South Pacific and the South Atlantic. The image inside the map neatline is georeferenced to the surface of the earth and fit to the 'World Mercator' projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, cities and other human settlements, territorial boundaries, shoreline features, and more. Relief shown by hachures. Depths shown by soundings. Includes routes, locations, and dates of James Cook's voyages. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map Showing Routes of Exploration and Discovery, 1790 (Image 5 of 8) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Chart of the world on Mercators projection : exhibiting all the new discoveries to the present time, with the tracks of the most distinguished navigators since the year 1700 carefully collected from the best charts, maps, voyages, &c. extant and regulated from the accurate astronomical observations made in three voyages performed under the command of Captn. James Cook in the years 1768, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 & 80, compiled and published by A. Arrowsmith, geographer; by permission of Simon McTavish Esq[r] is correctly delineated the discoveries of Mr. McKenzie laid down from his original journal in the year 1789. It was published by A. Arrowsmith, April 1, 1790. Scale [ca. 1:20,000,000]. This layer is image 5 of 8 total images of the seven sheet source map. Covers portions of North America, northern South America, and the western coasts of Europe and Africa. The image inside the map neatline is georeferenced to the surface of the earth and fit to the 'World Mercator' projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, cities and other human settlements, territorial boundaries, shoreline features, and more. Relief shown by hachures. Depths shown by soundings. Includes routes, locations, and dates of James Cook's voyages. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map Showing Routes of Exploration and Discovery, 1790 (Image 4 of 8) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Chart of the world on Mercators projection : exhibiting all the new discoveries to the present time, with the tracks of the most distinguished navigators since the year 1700 carefully collected from the best charts, maps, voyages, &c. extant and regulated from the accurate astronomical observations made in three voyages performed under the command of Captn. James Cook in the years 1768, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 & 80, compiled and published by A. Arrowsmith, geographer; by permission of Simon McTavish Esq[r] is correctly delineated the discoveries of Mr. McKenzie laid down from his original journal in the year 1789. It was published by A. Arrowsmith, April 1, 1790. Scale [ca. 1:20,000,000]. This layer is image 4 of 8 total images of the seven sheet source map. Covers portions of Southern Africa, Southeast Asia, Western Australia, and the Indian Ocean. The image inside the map neatline is georeferenced to the surface of the earth and fit to the 'World Mercator' projection. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. This map shows features such as drainage, cities and other human settlements, territorial boundaries, shoreline features, and more. Relief shown by hachures. Depths shown by soundings. Includes routes, locations, and dates of James Cook's voyages. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.

World Map Showing Routes of Exploration and Discovery, 1790 (Image 6 of 8) (Raster Image)

This layer is a georeferenced raster image of the historic paper map entitled: Chart of the world on Mercators projection : exhibiting all the new discoveries to the present time, with the tracks of the most distinguished navigators since the year 1700 carefully collected from the best charts, maps, voyages, &c. extant and regulated from the accurate astronomical observations made in three voyages performed under the command of Captn. James Cook in the years 1768, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79 & 80, compiled and published by A. Arrowsmith, geographer; by permission of Simon McTavish Esq[r] is correctly delineated the discoveries of Mr. McKenzie laid down from his original journal in the year 1789. It was published by A. Arrowsmith, April 1, 1790. Scale [ca. 1:20,000,000]. This layer is image 6 of 8 total images of the seven sheet source map. Covers portions of Australia, Southeast Asia, and the South Pacific Ocean. The image inside the map neatline is georeferenced to the surface of the earth and fit to a non-standard 'World Mercator' projection, with the central meridian at 180 degrees west. All map collar and inset information is also available as part of the raster image, including any inset maps, profiles, statistical tables, directories, text, illustrations, index maps, legends, or other information associated with the principal map. Note: The central meridian of this map is not the same as the Prime Meridian and may wrap the International Date Line or overlap itself when displayed in GIS software. This map shows features such as drainage, cities and other human settlements, territorial boundaries, shoreline features, and more. Relief shown by hachures. Depths shown by soundings. Includes routes, locations, and dates of James Cook's voyages. This layer is part of a selection of digitally scanned and georeferenced historic maps from the Harvard Map Collection and the Harvard University Library as part of the Open Collections Program at Harvard University project: Organizing Our World: Sponsored Exploration and Scientific Discovery in the Modern Age. Maps selected for the project correspond to various expeditions and represent a range of regions, originators, ground condition dates, scales, and purposes.