At Vertical Mapping Resources, Inc., our softcopy (digital) mapping equipment is the most advanced in the industry. Some of the procedures performed on these workstations consist of:
Aerotriangulation is a digital photogrammetric method for establishing additional and supplemental ground control within a project area. This process, which is a standard procedure in the aerial mapping realm, is performed to achieve a densified control block without the need for full ground control (4-5 panels per stereomodel). This offers a huge savings in overall cost to our clients, while still maintaining the accuracy of the control network and the resulting photogrammetric products.
This routine begins when the GPS ground control is loaded into the AT software, next the fiducials on the digitally scanned photographs are measured and interior orientation is computed. The system, either automatically or operator assisted, then selects and measure all passpoints and tiepoints. The relative orientation is computed and will show all residuals on the points measured. The final output from the bundle adjustment will supply all of the parameters that are needed to set up the softcopy stereo equipment for the ensuing topographic mapping.
Softcopy Compilation / Digital Terrain Modeling
Stereo digitizing is performed on Z/I Imaging digital photogrammetric workstations. These workstations utilize CADmap/dgn mapping software, which provides a superior, easy to use, map feature digitizing system for use with stereo scanned imagery. These workstations allow for efficient, accurate data collection while allowing for the ability to easily customize the data to individual client needs (format, layering, symbology, etc.).
Feature Collection is the process of tracing non-surface, or cultural, terrain features (planimetrics) within the stereo-model, such as curb-lines, building footprints, transportation lines, vegetation and the like. All discernible planimetric features are collected and digitized in conformance with each client's CAD standards for data parameters such as layering, line-weight, line-type and entity color. VMR stereo compilers employ 3D digitizing techniques to trace, or pinpoint, features. Digitized features are joined visually as well as digitally with no edge match tolerance.
A digital terrain model (DTM) is the basis for all contouring, orthophotography, TIN calculations and other surface modeling. The DTMs collected on the Z/I workstations are comprised of mass points and breaklines; which delineate various terrain defining features, such as ravines, ridges, tops and toes of slopes, as well as mass elevation grid points used in flatter areas. Unless client specified, VMR always collects a full DTM on every project in order to provide the most accurate surface model possible in order to meet and exceed FGDC accuracies.
Digital Mapping Services include:
- Softcopy Analytical Aerotriangulation
- Digital Elevation Models (DEMs) (Mass Points)
- Digital Terrain Models (DTMs)
- Planimetric Mapping
- Topographic mapping
- Volume Calculations
- Contour Generation
- 3-D Feature Extraction/Elevations
- GIS Update Mapping
- Change Detection
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