This report is devoted to the method of geophysical research results presentation as isoline maps based on compound digital models (matrixes, or grids), illustrated by the example of the Geomap-1000 sheet R-38-40, which covers the sea area of Timano-Pechorsky gas-and-oil basin.
To create these models the vast experience of non-uniformly scaled surveys carried out by different organizations has been summarized, which made possible acquiring the interconnected by the field level data and a number of their transformations (residual abnormalities, horizontal and vertical gradients).
Isoline mapping was based on field digital models. This method of geophysical research result presentation, developed by our group, consists of 3 phases: isoline calculation after a digital model (matrix), isoline adjustment and their type-out pretreatment. The second phase, when calculated isolines get adjusted to the map criterions, is fundamentally important (f.e. fine "pea" isolines get eliminated, sharp edges get smoothened). This procedure made impossible report maps generation with "Surfer" program.
The first phase - isoline calculation process is presently based on the standard plug-in module "Spatial Analyst" for "Arc View" computer program and specially designed modules use. Matrixes are imported to "Arc View" where all the necessary calculations are carried out. The resulted data are ready for processing. Isolines calculated in "Surfer 7" can be later exported to "Unimap" or "ArcView".
During the second phase "Unimap" program is mainly used. This program has usable interface and complete set of tools for work with geographical objects (creation, deleting, cutting, joining, lines smoothening, points adding, deleting, moving on line and separate objects). Essential feature of this program is line attributes support (including table form), which make it an ideal tool for such kind of work. It is necessary to mention that the program can vectorize any of existing fixed maps. Basing on the scanned image it can create topologically proper digital map copies, which can be recalculated for desired geographical projection in main geoinformational systems formats (ArcInfo, ArcView, Autocad, GIS PARC, etc.) E.G. Vasilyeva has designed a special object correction module for "ArcView" program.
Fig. 1. Gravimetric map for sheet R-38-40
The final phase. It is carried out with the specially designed "Arcview" scripts. During this phase topology is calculated (if it hasn't been performed in "Unimap"), then coloring takes place, the scale and grid are made, isolines and berg-strokes are marked, and finally the map is arranged according to the mapping standards.
The result of the work is proper digital model of geophysical field in GIS "Arcview" ready for printing (Fig. 1). The received maps serve geographical basis for the corresponding sheets.