Photographing of terrain on the ground and objects in the air by cameras mounted in aircraft; utilized in satellites, multispectral scanning and intricate data handling systems.
Also referred to as aerial photo or air photo
A map showing certain fundamental information used as a base upon which additional data of specialized nature are compiled.
A non-reproducible blue image printed on paper from vellum or mylar sheet.
An elevation polyline, in which each vertex has its own X,Y,Z values.
Computer Aided Drafting/Design/Drawing.
CAD originated on larger, dedicated workstations and minicomputers and has now migrated to microcomputers. In its simplest sense, CAD is used for computerized drafting. Many CAD systems also provide more advanced features like solid modeling and simulation. CAD generally lacks topology of objects and direct links to an attribute database, which are essential features in GIS modeling and analysis operations.
A set of information depicting the pattern of land ownership rights in an area. The layer is typically based on legal descriptions tied to elements of the geodetic control network available in an area.
A map showing boundaries of subdivision of land for purposes of describing and recording ownership.
An imaginary line on a land surface connecting points of equal elevation.
A procedure involving a detailed review and cleansing of the data the purpose of which is to eliminate errors both visual and tabular prior to loading to the geospatial data repository.
A geodetic reference system that specifies the size and shape of the earth, and the base point from which the latitude and longitude of all other points on the earth’s surface are referenced.
A scale for which data source has been designed or selected to ensure product accuracy. In derived products, the design scale is the smallest scale of individual features.
Formerly known as PUCC, the Digital Map Owners Group (DMOG) is a nine-member sub-committee of the Toronto Public Utility Co-ordinating Committee (TPUCC), sharing in the cost of maintenance of the underground utilities of the former City of Toronto.
A Digital Terrain Model is a land surface represented in digital form by an elevation grid or lists of three-dimensional coordinates.
A geospatial process that is invaluable for those who wish to match their business information to a geographic element.
As an example, the issuance of a parking ticket (containing an address) can be spatially related to the City’s geography by the address on the ticket.
A database or file structure used primarily to store, query, and manipulate spatial data.
A system used to measure horizontal and vertical distances on a planimetric map. The City of Toronto’s operational co-ordinate system is currently the Modified Transverse Mercator (MTM) projection, North American Datum 1927 (NAD27), with a truncated northing or y value (-4,000,000).
A GIS operation automated and used to manipulate data stored in a GIS workspace, personal geodatabase,or shared geodatabase. A typical geoprocessing operation takes an input dataset, performs an operation, and returns the result as an output dataset, then a report tabular or graphic is produced showing the results.
Common geoprocessing operations are geographic feature overlay, feature selection and analysis, topology processing, and data conversion.
The fundamental purpose of geoprocessing is to allow you to automate your GIS tasks, analysis, and linking and displaying data geographically
A process of assigning map co-ordinates to image data to conform to map projection grid.
Loading of data or geospatial layers of information into the enterprise geospatial data repository so that it made available by the many users who access the city’s central repository of geographic data.
Also known as the enterprise data warehouse of geospatial information, SDE, or data warehouse, It is the central location of geospatial data for the city where staff can access different layers of information.
Please note that SDE is actually the software that accesses the geospatial repository and for a complete description please refer to the SDE definition.
An integrated collection of computer software and data used to view and manage information about geographic places, analyze spatial relationships, and model spatial processes. A GIS provides a framework for gathering and organizing spatial data and related information so that it can be displayed and analyzed.
A level of detail in data. For example, ground pixel distance in aerial photography.
The area represented by each pixel of a satellite image. The smaller the area represented by a pixel, the more accurate and detailed the image. For example, if a U.S. map and a world map are printed on identically sized sheets of paper, one square inch on the U.S. map will represent far less area and provide for more detail than one square inch on the world map. In this example the U.S. map has higher resolution. The imagery viewable with ToMaps has a resolution of 50 centimetres.
A description used to represent a map or data file having a large ratio between the area on the map and the area that is represented. If the map the size of this page shows only a small area such as your house, it would be described as large-scale mapping.
A mathematical model that transforms the locations of features on the Earth’s surface to locations on a two-dimensional surface such as a map.
There is a certain give and take as some projections preserve shape; others preserve accuracy of area, distance, or direction.
See also coordinate system
The ratio of a distance on a map to the true distance on the ground. For example, if the map scale is 1:1000, 1cm on the map represents 10 m on the ground.
See also Design Scale
An aerial photograph or satellite scene that has been transformed by the orthogonal projection, yielding a map that is free of most significant geometric distortions.
A form of rectification that corrects for terrain displacement.
See also Rectification
The art and science and technology of obtaining reliable information about physical objects and the environment through a process of recording, measuring, and interpreting images and patterns of electromagnetic radiant energy and other phenomena.
A map that represents only the horizontal positions for the features represented.
Features include: roads, buildings, water, fences, vegetation, bridges, railroads,etc.
It has constant lengths, angles, and areas across the two dimensions and is always based on a geographic coordinate system.
The locations are identified by x,y coordinates on a grid, with the origin at the centre of the grid. Each position has two values that reference it to that central location. One specifies its horizontal position and the other its vertical position. The two values are called the x-coordinate and y-coordinate.
Public Utilities Coordinating Committee.
See DMOG.
A GCC service where clients’ data is reviewed and a report produced with our findings and recommendations.
For example, a business unit provides addresses with business information to GCC. GCC does a geocoding exercise and produces a report with kick-outs or unmatched addresses. The report includes explanation as to why address did not match.
A matrix of cells (or pixels) organized into rows and columns (or a grid) where each cell contains a value representing information, such as temperature. Rasters are digital aerial photographs, imagery from satellites, digital pictures, or even scanned maps.
A process of making image data conform to a map projection.
A type of database that stores data in a structure consisting of one or more tables of rows and columns, which may be interconnected with each other through common fields. A row corresponds to a record (tuple); columns correspond to attributes (fields) in the record. Typically use Structured Query Language (SQL) for data definition, data management, and data access and retrieval.
A level of detail in data. For example, ground pixel distance in aerial photography.
The area represented by each pixel of a satellite image. The smaller the area represented by a pixel, the more accurate and detailed the image. For example, if a U.S. map and a world map are printed on identically sized sheets of paper, one square inch on the U.S. map will represent far less area and provide for more detail than one square inch on the world map. In this example the U.S. map has higher resolution. The imagery viewable with ToMaps has a resolution of 50 centimetres.
Spatial analysis is the process of modelling, examining and interpreting results based on geographic phenomena with their spatial dimensions and their associated attributes. Spatial analysis is useful for evaluating suitability and capability, for estimating and predicting, and for interpreting and understanding.
SDE is a software product from Environmental Systems Research Institute that stores GIS data in a relational database, such as Oracle or Informix. SDE manages the data inside of tables in the database, and handles data input and retrieval. All vector data in HP Graphic Language (HGL) is stored using SDE in an Oracle database.
A point on a map whose height above a specified reference datum is noted, usually by a dot and elevation. Also called Spot height.
The science and art that deals with the use of binocular vision or observation of a pair of overlapping photographs.
A land surface model based on triangles. A specific representation of DTM in which elevation points can occur at irregular intervals.
Map that presents the horizontal and vertical positions of the features represented. It is distinguished from a planimetric map by the addition of relief in measurable form.
Topopgraphic features pertain to the accurate graphical description, usually on maps or charts, of the physical features (hills, shorelines, relief, etc) of an area on the Earth.
Universal Transverse Mercator (UTM) system is a specialized application of the Transverse Mercator projection. The globe is divided into 60 north and south zones, each spanning 6° of longitude. Each zone has its own central meridian. Zones 1N and 1S start at -180° W. The limits of each zone are 84° N and 80° S, with the division between north and south zones occurring at the equator. The polar regions use the Universal Polar Stereographic coordinate system.
The origin for each zone is its central meridian and the equator. To eliminate negative coordinates, the coordinate system alters the coordinate values at the origin. The value given to the central meridian is the false easting, and the value assigned to the equator is the false northing. A false easting of 500,000 meters is applied. A north zone has a false northing of zero, while a south zone has a false northing of 10,000,000 meters.
One method of storing, representing or displaying spatial data in digital form. It consists of using coordinate pairs (x,y) to represent locations on the earth. Features can take the form of single points, lines, arcs or closed lines (polygons)