THE READABILITY OF THE MAP: THEORETICAL PRINCIPLES

An effort is made at developing a theory of map readability, defined as the process of the user's representation of the information of the map in his/her own mind. This can be estimated quantitatively by surrogate measures, which include the speed of map comprehension and accuracy of map interpretation. Levels of psychological representation of map information are incorporated to determine at what stage particular aspects of map knowledge are understood. Thus what readability entails, and the approaches used to measure it (what types of things are comprehended, how fast, and how accurately) will depend upon the level of representation. Translated from: Vestnik Leningradskogo Universiteta, seriya 7 [geologiya, geografiya], 1988, No. 1, pp. 32-37.     

EXPERIENCE IN COMPILING LARGE-SCALE MAPS OF EROSION-PRONE AREAS

Specific criteria used in the compilation of large-scale maps of erosion-prone areas are defined and evaluated for tracts of land representing a number of different agricultural cover types. Formulas are derived which facilitate the mapping of such areas based on such readily observable morphometric characteristics as slope length and steepness. Translated by Edward Torrey, Alexandria, VA 22308 from: Vestnik Moskovskogo Universiteta, geografiya, 1988, No. 5, pp. 25-31.     

THE PRESENT STATE OF ECOSYSTEMS IN MONGOLIA: PRINCIPLES OF EVALUATION AND MAPPING

This paper explores how such characteristics as the polarization of reflected radiation, the angular characteristics of its reflectance, and its thermal properties can be used to supplement conventional remote sensing studies of the condition of the vegetation cover. One possible application is clarified by means of an experiment testing the relationship between the degree of polarization of radiation reflected from cultivated cotton fields and the condition of the crop in those fields. Empirical data demonstrate that changes in the geometric structure of (and reflectance from) fields occurs when cultivated plants are subjected to stress (disease or moisture deprivation). Translated by Edward Torrey, Alexandria, VA 22308 from: L. N. Vasil'yev, ed., Kosmicheskiye metody izucheniya biosfery [Remote Sensing Methods in the Study of the Biosphere]. Moscow: Nauka, 1990, pp. 77–82.     

COMPUTATION AND MAPPING OF THE ELEMENTS OF THE WATER-ICE BUDGET OF GLACIERS

Two general approaches for compiling maps of components of the water-ice budget in regions of glacier nourishment are compared and the resulting maps are analyzed. The compilation of raw data is based on field measurements rather than remote sensing information. Translated by Edward Torrey, Alexandria, VA 22308 from: Materialy glyatsiologicheskikh issledovaniy, 1991, No. 72, pp. 94-102.     

ECOLOGICAL ASSESSMENT AND MAPPING FOR BALANCED REGIONAL DEVELOPMENT

A Russian geographer summarizes the results of a comprehensive study of modern landscapes and the mapping of diverse ecological situations. The procedure involves the development of a system of criteria and indices for the assessment of the properties of the environment, which provide a sound basis for comprehensive ecological mapping. The importance of an ecological assessment in the mapping of environmental problems and situations in support of the stable and balanced development of regions is demonstrated. Translated by Edward Torrey, Alexandria, VA from: Izvestiya Akademiya Nauk, seriya geograficheskaya, 1999, No. 1, pp. 81-87.     

Global geospatial data from Earth observation: status and issues

ABSTRACT

Data covering the whole of the surface of the Earth in a homogeneous and reliable manner has been accumulating over many years. This type of data became available from meteorological satellites from the 1960s and from Earth-observing satellites at a small scale from the early 1970s but has gradually accumulated at larger scales up to the present day when we now have data covering many environmental themes at large scales. These data have been used to generate information which is presented in the form of global data sets. This paper will give a brief introduction to the development of Earth observation and to the organisations and sensors which collect data and produce global geospatial data sets. Means of accessing global data sets will set out the types of data available that will be covered. Digital elevation models are discussed in a separate section because of their importance in georeferencing image data as well as their application to analysis of thematic data. The paper will also examine issues of availability, accuracy, validation and reliability and will look at future challenges.     

A data-driven approach to local gravity field modelling using spherical radial basis functions

We propose a methodology for local gravity field modelling from gravity data using spherical radial basis functions. The methodology comprises two steps: in step 1, gravity data (gravity anomalies and/or gravity disturbances) are used to estimate the disturbing potential using least-squares techniques. The latter is represented as a linear combination of spherical radial basis functions (SRBFs). A data-adaptive strategy is used to select the optimal number, location, and depths of the SRBFs using generalized cross validation. Variance component estimation is used to determine the optimal regularization parameter and to properly weight the different data sets. In the second step, the gravimetric height anomalies are combined with observed differences between global positioning system (GPS) ellipsoidal heights and normal heights. The data combination is written as the solution of a Cauchy boundary-value problem for the Laplace equation. This allows removal of the non-uniqueness of the problem of local gravity field modelling from terrestrial gravity data. At the same time, existing systematic distortions in the gravimetric and geometric height anomalies are also absorbed into the combination. The approach is used to compute a height reference surface for the Netherlands. The solution is compared with NLGEO2004, the official Dutch height reference surface, which has been computed using the same data but a Stokes-based approach with kernel modification and a geometric six-parameter “corrector surface” to fit the gravimetric solution to the GPS-levelling points. A direct comparison of both height reference surfaces shows an RMS difference of 0.6 cm; the maximum difference is 2.1 cm. A test at independent GPS-levelling control points, confirms that our solution is in no way inferior to NLGEO2004.     

High-Resolution Forecast Models of Water Vapor Over Mountains: Comparison With MERIS and Meteosat Data

Propagation delay due to variable tropospheric water vapor (WV) is one of the most intractable problems for radar interferometry, particularly over mountains. The WV field can be simulated by an atmospheric model, and the difference between the two fields is used to correct the radar interferogram. Here, we report our use of the U.K. Met Office Unified Model in a nested mode to produce high-resolution forecast fields for the 3-km-high Mount Etna volcano. The simulated precipitable-water field is validated against that retrieved from the Medium-Resolution Imaging Spectrometer (MERIS) radiometer on the Envisat satellite, which has a resolution of 300 m. Two case studies, one from winter (November 24, 2004) and one from summer (June 25, 2005), show that the mismatch between the model and the MERIS fields ( rms = 1.1 and 1.6 mm, respectively) is small. One of the main potential sources of error in the models is the timing of the WV field simulation. We show that long-wavelength upper tropospheric troughs of low WV could be identified in both the model output and Meteosat WV imagery for the November 24, 2004 case and used to choose the best time of model output.     

Hyperspectral anomaly detection within the signal subspace

This letter describes the extension of signal subspace processing (SSP) to the arena of anomaly detection. In particular, we develop an SSP-based, local anomaly detector that exploits the rich information available in the multiple bands of a hyperspectral (HS) image. This SSP approach is based on signal processing considerations, and its entire formulation reduces to a straightforward (and intuitively pleasing) geometric and algebraic development. We extend the basic SSP concepts to the HS anomaly detection problem, develop an SSP HS anomaly detector, and evaluate this algorithm using multiple HS data files.     

Generalization of total least-squares on example of unweighted and weighted 2D similarity transformation

In this contribution it is shown that the so-called “total least-squares estimate” (TLS) within an errors-in-variables (EIV) model can be identified as a special case of the method of least-squares within the nonlinear Gauss–Helmert model. In contrast to the EIV-model, the nonlinear GH-model does not impose any restrictions on the form of functional relationship between the quantities involved in the model. Even more complex EIV-models, which require specific approaches like “generalized total least-squares” (GTLS) or “structured total least-squares” (STLS), can be treated as nonlinear GH-models without any serious problems. The example of a similarity transformation of planar coordinates shows that the “total least-squares solution” can be obtained easily from a rigorous evaluation of the Gauss–Helmert model. In contrast to weighted TLS, weights can then be introduced without further limitations. Using two numerical examples taken from the literature, these solutions are compared with those obtained from certain specialized TLS approaches.