Desktop Mapping System (DMS) - Digital Orthophotos from Start to Finish

The Original Desktop Mapping System 4.2 is a full featured softcopy photogrammetric software package for use on personal computers. DMS is designed to facilitate mapping from stereo and monoscopic image data in digital format, including scanned aerial photographs and satellite images.

A full complement of image processing routines perform enhancement and data management functions. Rigorous photogrammetric solutions are employed to extract accurate coordinate information from scanned aerial photographs for use in automated generation of digital elevation models (DEMs), relief corrected planimetry, contours and digital orthophotos. Functions facilitate point measurement and transfer for aerotriangulation and image-to-image registration tasks. Planimetric mapping capabilities provide functions for vector map compilation and revision using rectified and non-rectified images as a raster backdrop.

DMS Software Specifications

Softcopy Photogrammetry

The Desktop Mapping System provides a rigorous softcopy photogrammetric solution for use with scanned aerial photographs. Stereomodels are viewed in anaglyph 3D for topographic mapping, map compilation and map revision. The stereomodels may also be employed for DEM generation using automated stereocorrelation techniques. With the DEM generated by stereocorrelation or obtained from agencies such as the U.S. Geological Survey (USGS) or Defense Mapping Agency (DMA), air photos and satellite images can be quickly converted to orthoimages.

Image Display and Enhancement

Image, GIS, DEM or vector files may be displayed. Raster images can be zoomed and X, Y, and Z map coordinates, pixel and line coordinates and digital number values recovered by moving the cursor throughout the image. Image enhancements maximize image contrast and improve interpretability for mapping applications. A histogram equalization algorithm is applied to the image pixels and increases the contrast in the image by expanding the range of digital numbers (DN). The l-H-S Transformation permits the integration of two or more multispectral/ multiresolution /multitemporal data sets. A typical application of the IHS Transformation is to create a high resolution color image by integrating SPOT Panchromatic data with SPOT XS or Landsat Thematic Mapper multispectral image data. Filters are used to sharpen detail in an image or smooth a DEM.

Geocoding and Image Registration

Raster data files may be geocoded to create new geometrically correct (rectified) data files referenced to a standard coordinate system. The development of registered image data sets for use in GIS applications is automated and readily accomplished.

Points, lines and/or closed polygons traced with a digitizing tablet from maps, aerial photographs, or other hardcopy can be rectified using control points. The resulting coordinates are assigned feature codes/ attributes and stored in GCP or vector files. Ground control points can also be obtained from digital (scanned) map or rectified image data using on-screen digitizing procedures

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Softcopy Photo Interpretation

Geocoded raster images provide an excellent base for compiling or revising planimetric maps. Vector files can be established by tracing point, line and polygon features from an image on the display screen. In addition, existing map files in vector format can be overlaid on an image or GIS file for the purpose of map revision or accuracy checking.

Interactive Stereo Mapping

Spot heights, contours and planimetry can be compiled from stereo air photo and satellite image data in digital format. After a stereo model is formed, it can be viewed in 3D and a floating mark employed to measure planimetric map coordinates and elevations. Output is a vector data file of X, Y, Z coordinates corresponding to relief corrected planimetry, spot heights and contours.

Digital Elevation Models (DEM's)

DEMs are created using automated stereocorrelation techniques with a user-specifed grid spacing for a stereo image data set. The DEM can then be rectified, used to generate an orthophoto or overlaid with the original image data for terrain visualization. DEMs generated with stereocorrelation from stereo satellite images may be edited. The stereo image is viewed in 3D and the DEM overlaid on top of the image as a grid of floating dots. Erroneous points in the DEM will be apparent because they will appear to either be above or below the ground surface. Using the mouse, posts can be corrected and saved.

Orthoimage Production

Relief displacements may be removed from single satellite or scanned air photo image data sets to create orthoimages. A DEM must be provided either through the use of stereocorrelation techniques, photogrammetry or obtained from another source. The output image will have all of the effects of relief displacement removed.

Digital Image Mosaics

The DMS permits rectified scanned aerial photographs, orthoimages, satellite images and DEM files to be mosaicked together to create a larger file. Multiple vector files also can be merged to form a single file.

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Terrain Visualisation

A DEM can be displayed as a 3D perspective diagram. The 3D wireframe can be interactively tilted, rotated and scaled until the best view is obtained. An image or GIS file or color-coded elevations can then be draped. The wireframe may also be viewed in 3D using anaglyph methods. Screen images and viewing geometry may be saved for quick redisplay or hardcopy production.

Aerotriangulation

Point measurement and transfer functions are provided to facilitate GCP and pass point identification for use in aerotriangulation. DMS supports PC GIANT and AeroSys aerotriangulation packages operational under Windows. Additional translators may be provided upon request.

Thematic Classification

Supervised classification techniques are employed to identify pixels corresponding to specific themes such as land use/cover classes which are stored as a GIS file. Images also may be manually interpreted to delineate specific areas. The resulting thematic classes are then color-coded for display.

Vector to Raster Conversion

A vector file may be converted to a raster format for further analysis in a raster GIS modeling package. The output raster GIS file may have any pixel size and will be rectified according to the map coordinate system and the user-defined origin coordinates. This feature permits exact registration of existing image/GIS files to the same coordinate system. The rasterized vectors can be "burned" into an existing image or GIS file for display.

GIS Interface and Data Conversion

Image and vector files generated with DMS are compatible with industry-standard GIS packages such as ArcView. In addition, DMS reads ESRI Arc/lnfo Generate format vectors directly without conversion for vector-on-raster overlay. Other commercial GIS packages that DMS can interchange vector and raster data with include ERDAS, AutoCAD, GEO/SQL, Atlas*GIS, Idrisi and GRASS. DMS can also import TIGER, ETAK and USGS DLG-3 files.

Import/Export DEM Data

DMS will convert an ASCII 1:24,000 scale USGS DEM, as well as other ASCII formats, to DMS format. Defense Mapping Agency 1:250,000 scale DTED files also may be utilized in DMS for the purposes of terrain visualization and orthophoto production. DMS DEM files can be exported to both USGS DEM and DMA DTED formats, if desired.

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