Integration of Car tracking GPS with mapping program Assistance
GPS Visualizer is a slick, easy-to-use Web-based mapping program, written by Adam Schneider, that allows you to upload GPS waypoints and track files to a Web site and then overlay them on topographic and other types maps. GPS Visualizer relies on online sources that provide free topographic maps, aerial photos, satellite images, and street maps. Unlike many other sites that are limited to making maps of the United States, GPS Visualizer can create maps of Canada, Europe, and other places in the world. GPS Visualizer has a number of powerful options for creating customized maps. In this section, I describe how to make a map using some of the Web site’s basic features. After you master the general procedure, you can experiment on your own with some of the other advanced options.
Map aiding is most useful when map matching has determined that the vehicle has just turned a corner, in which case its position is in close proximity to the intersection of two streets of a known location in the map database. This reference position may be treated as a single position fix by the integration filter, which serves to correct or improve the accuracy of the absolute position determined by GPS tracker. Further, if map matching has determined, with high probability, that the vehicle is traveling on a specific road in the database and that road is straight, then a heading fix may be generated for the integration filter based on the bearing of that road segment according to the map database. Another way to utilize the heading information after a turn is to impose a constraint on the model to force the heading of the vehicle to match the bearing of the road. Map feedback can be used instead of DR sensors to improve the performance of GPS in low-cost navigation systems.
In addition to the horizontal position components of road vectors, ground elevation data may be used to augment the performance of GPS. A digital terrain model (DTM) is a representation of the Earth’s surface that can be used to extract elevation data. A digital elevation model (DEM) is a type of DTM with a regularly spaced grid of elevations corresponding to the elevation of the Earth’s terrain at that point. Modern DTMs are derived from airborne or satellite-based remote sensors, are georeferenced using tracking device coordinates, and have vertical accuracies better than 10m. Terrain elevation can be used to improve the accuracy associated with GPS fixes for land applications. As is well known, and addressed previously in the text, the vertical axis is the weakest part of the GPS solution. Terrain elevation data, if sufficiently accurate, can be added as a constraint to a least squares or WLS GPS fix or added as a measurement to a real-time Kalman filter.
To apply a height constraint an approximate or previous position can be used to extract the corresponding elevation from a DTM, DEM, or other source of elevation data. If the terrain elevation varies greatly in the vicinity of the position, iteration may be necessary. Using a DEM for this purpose may be easier from a computational perspective, since it would involve a simple value lookup and interpolation based on the coordinates; however, a large amount of storage would be required for the DEM. A DTM that has the elevation data organized into vectors would use less storage but would require more complicated computations to determine the elevation at a specific point. Elevation data can also be integrated into digital road maps as attribute data, which would simplify elevation lookup and keep the storage requirements lower. Terrain elevation data has not yet been used widely to augment GPS Tracking Device; this will likely change in navigation and driver safety systems once elevation information is integrated into digital road maps.
Map aiding is most useful when map matching has determined that the vehicle has just turned a corner, in which case its position is in close proximity to the intersection of two streets of a known location in the map database. This reference position may be treated as a single position fix by the integration filter, which serves to correct or improve the accuracy of the absolute position determined by GPS tracker. Further, if map matching has determined, with high probability, that the vehicle is traveling on a specific road in the database and that road is straight, then a heading fix may be generated for the integration filter based on the bearing of that road segment according to the map database. Another way to utilize the heading information after a turn is to impose a constraint on the model to force the heading of the vehicle to match the bearing of the road. Map feedback can be used instead of DR sensors to improve the performance of GPS in low-cost navigation systems.
In addition to the horizontal position components of road vectors, ground elevation data may be used to augment the performance of GPS. A digital terrain model (DTM) is a representation of the Earth’s surface that can be used to extract elevation data. A digital elevation model (DEM) is a type of DTM with a regularly spaced grid of elevations corresponding to the elevation of the Earth’s terrain at that point. Modern DTMs are derived from airborne or satellite-based remote sensors, are georeferenced using tracking device coordinates, and have vertical accuracies better than 10m. Terrain elevation can be used to improve the accuracy associated with GPS fixes for land applications. As is well known, and addressed previously in the text, the vertical axis is the weakest part of the GPS solution. Terrain elevation data, if sufficiently accurate, can be added as a constraint to a least squares or WLS GPS fix or added as a measurement to a real-time Kalman filter.
To apply a height constraint an approximate or previous position can be used to extract the corresponding elevation from a DTM, DEM, or other source of elevation data. If the terrain elevation varies greatly in the vicinity of the position, iteration may be necessary. Using a DEM for this purpose may be easier from a computational perspective, since it would involve a simple value lookup and interpolation based on the coordinates; however, a large amount of storage would be required for the DEM. A DTM that has the elevation data organized into vectors would use less storage but would require more complicated computations to determine the elevation at a specific point. Elevation data can also be integrated into digital road maps as attribute data, which would simplify elevation lookup and keep the storage requirements lower. Terrain elevation data has not yet been used widely to augment GPS Tracking Device; this will likely change in navigation and driver safety systems once elevation information is integrated into digital road maps.
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