Planimetric Features Research Articles

Airborne SAR stereo restitution in a mountainous area of Costa Rica: first results

This paper presents a fully digital method for the stereo extraction of planimetric and altimetric features from digital airborne SAR data in stereoscopic mode. The method uses a photogrammetric approach. Image analysis is done with a digital stereo workstation (DVP) using a low-cost hardware (PC). To test the limits of the DVP system with actual data, a challenging airborne SAR stereopair was used from a mountainous area (2,000 m) in the Cordillera Centrale (Costa Rica) from the SAREX-92 mission. Compared with a 1:50000 topographic map, the first results show a planimetric accuracy of 20-35 m for well identifiable features and an altimetric accuracy of 40-50 m. These results have to be confirmed with more precise digital topographic data.

Matching information in overlapping photogrammetric models

Processing data collected in overlapping areas of neighbouring models usually poses a problem of merging strings of points related to planimetric and topographic features. A solution of that problem based on automatic identification of pairs of corresponding strings of points located in the overlapping areas, and on weighting the data participating in the merging procedure is discussed. The procedure is independent of the order in which the models are being evaluated. It provides a unique description of the features and is highly automated. Only a small number of cases remain unresolved, thus requiring human assistance.

A base mapping program for Wyandotte County, Kansas (a multipurpose land records information system)

Wyandotte County, Kansas, has developed a parcel-level land records system over the past 10 years, accomplished primarily by the staff of the County Base Mapping Program. The graphic component of the system is a digital map of the boundaries of ownership parcels based on recorded deeds. The non-graphic component is a common data base with records on land parcels, designed to be easily accessible, easily maintained, flexible for new applications and expandable for new data elements. The positions of parcel boundaries in the digital map have been reconciled with the positions of all planimetric features shown on the large-scale topographic base maps. However, the mapping of boundaries is only gradually being reconciled with the legal descriptions of the properties, as the results of new surveys or other reviews of the legal records become available. This incremental approach to accuracy in mapping of cadastral boundaries has allowed the County to complete its digital map relatively quickly with sufficient accuracy for most users, while continuing to improve the precision of the map for eventual use for legal or engineering records which require higher standards. Topological relationships among parcels are recorded in the digitizing process, but the topology has been used to date only for editing of the digitized point data.

Acquisition et controle des donnees par photogrammetrie numerique a grande echelle

Digital data acquisition techniques through large-scale photogrammetry are reviewed, including not only data measuring and recording, but also checking and editing, since these phases have to be performed before inserting data into data banks, and automatic compiling and plotting as well. Various methods of acquisition and editing in use at the time fall into several categories, based upon different criteria: direct or indirect acquisition (direct from the stereomodel, indirect from an intermediate two-dimensional support), the degree of automation according to the nature of the desired informations, and the role of the computer (off-line or on-line) in correlation with new man-machine relationships. In conclusion, the author attempts to report significant trends such as: 1. (1) automation seems to develop particularly for altimetric data, directly digitized from the model, in connexion with automatic orthophotography, on-line or off-line print; 2. (2) planimetric features are also digitized directly from the model, with human interpretation and computer assistance, and in the most recent systems CRT displays and interactive data manipulation; 3. (3) however, many organizations use two-dimensional digitization from existing linemaps or orthophotographs, and display and editing procedures by batch processing; 4. (4) from a theoretical point of view stereoorthophotographs offer an intermediate solution with many advantages, since they are both planimetric and altimetric, can be digitized both in two or three dimensions and be entirely automatically produced; 5. (5) two series of problems still limit automation in large-scale photogrammetric digitizing and editing: automatic interpretation or pattern recognition, which is a general problem of image processing; and automatic revision, which is a general problem of data banks.

Applications of the random model of drainage basin composition

AbstractThe random model of drainage basin composition is founded on the assumptions that (a) natural channels are topologically random in the absence of geological controls and (b) for channel networks developed in similar environments, the exterior and interior link lengths are independent random variables with a common distribution for each type. The effectiveness of this model in estimating the values of geomorphic variables and in explaining and predicting geomorphic relationships is illustrated by several examples. The data required for these examples were obtained from map studies of 30 channel networks, comprising a total of about 8700 links, in eastern Kentucky. A common factor in the success of all three applications of the model is the way in which the planimetric features of drainage basins are determined by their underlying topologic structure.

MANUSCRIPT MAPS IN LATE IMPERIAL CHINA

This paper, based on collections of Oriental maps in the Library of Congress and in the British Museum, describes the cartographic characteristics of manuscript maps made in late Imperial China and evaluates their role in cartographic history in a world perspective. Chinese manuscript maps were constructed by local authorities in great numbers for various administrative, water control, military, and ideological purposes. While Chinese cartographers seemed quite content with much limited planimetric information, they devoted their efforts almost entirely to the perfection of symbolization and the visual effectiveness of map design for its own artistic value. Chinese maps were oriented in a few peculiar ways to serve functional and ideological needs. Pictorial map symbols which were so elaborately designed reflected a good deal of Chinese perception of physical and cultural features in various periods. The distortion and exaggeration of many planimetric features on these maps were associated with certain institutional and cosmological beliefs.