Geolink GIS::

GeoLink is a powerful multi-purpose geographic information system. Users can solve hydrogeological, cartographical, referential, statistical, environmental monitoring and many other problems with it. The system has many tools for spatial and hydrogeological modeling. Users can create their own applications that work in GeoLink environment.

GeoLink is widely used for hydrosphere processes monitoring and modeling. It's accepted as official GIS for the State Ground Water Monitoring information system of the Russian Federation.

System requirements::

GeoLink geographic information system was designed for work in Windows 95/98 and Windows NT environments. It doesn't require much from computer; broadly speaking, it can work with a minimum configuration required by the operating system. The optimum amount of RAM is 32 - 64 megabytes. System kernel requires only 12 MB of hard disk space for minimum installation.

GeoLink can work with any models of printers supported by the operating system.

WINTAB API is supported when working with digitizers. It means that the program can work with any of contemporary digitizers. It should be noted that a digitizer is required only if user wants to trace a map and isn't needed otherwise.

Vectorization and Editing of Geographic Data::

Geographic data (geographic objects) are stored in GeoLink geographic database in absolute geographic or metric coordinates. User can enter data into the database either by import or by map vectorization. Objects can be created as a result of one of the specialized applications work. Topological links between objects are always supported. The quality (validity) of the geographic data is of a particular importance in hydrogeology, so objects are always checked while being saved into the database. Objects stored in the database can be edited with a powerful vector editor provided for this purpose. The editor is also used to manage object inscriptions - each object can have several of them.
 

Map vectorization::

GeoLink has a convenient and powerful editor of vector objects. Maps can be vectorized either by tablet-based digitizing or over a map background; automatic tracing is not supported. When necessary, one can use any automatic vectorization program available, then import the obtained data. Input data can be edited with the vector editor supporting topological links between objects, which is very important for hydrogeology and spatial modeling.

Topological links between objects::

The vector editor of GeoLink allows establishing topological links between objects within the entire geographic database, no matter the layers these objects belong to. User can establish the links manually or automatically: program searches for the objects possibly linked to a particular object, then establishes the links, and user has to confirm or reject the new topology.
 

Validity of geographic objects::

The quality of the used geographic data plays a key role when solving many hydrogeological (and not only hydrogeological!) problems. In many cases usual data errors like self-crossing, duplicated points, etc., are simply inadmissible. In GeoLink the validity of an object, i.e. the compliance of its characteristics with those of the appropriate geographic layer, is checked directly while storing the object into the database; the continuity of contours, correct cyclization, duplicated points and self-crossings, etc., are also checked. On errors, some of them are corrected automatically - when possible, otherwise the object is stored in the database with a special flag of invalidity, and user can edit such objects afterwards. The invalid objects are supplied with a specific legend and are not accessible for certain specialized applications.

 

Map Design::

Map Plotting::

Map design starts from definition of geographic area, selection of geographic projection and map scale. Then user selects base layers and defines their legend. GeoLink arbitrary manages number of maps from different geographic databases simultaneously. Geographic objects are stored in a database either in absolute geographic coordinates with accuracy of 0.1 angular sec. or in metric coordinates with accuracy of 1 cm. One can use any scale and various basic cartographic projections. Both arbitrary and standard Gauss-Kruger plans are supported. Advanced tools for map legend editing allow user to design maps meeting necessary requirements. All maps built can be subsequently printed or exported as graphics.

Printing::

Maps built can be printed to any printer and WYSIWYG print preview is available. The map is automatically cut into separate sheets depending on the paper size. It is also possible to print map legend separately. To continue processing the map as an image, it can be exported into Windows Metafile or bitmap format and then transferred to external graphical package.

Gauss-Kruger plans::

The GeoLink supports standard Gauss-Kruger plans of any reasonable scale and projection. In many cases it considerably facilitates managing the geographic information, as well as grid data. It should be noted that it is also possible to show Cartesian and degree coordinate grids, specify image margins, etc., both for standard and arbitrary plans.

Map Legend Editing::

Handling map legend::

The majority of special-purpose maps, in particular geological and hydrogeological ones, have a complex legend. So a special attention in GeoLink is focused on peculiarities of object visualization. System allows using conventional and custom fillings, strokes, lines and symbols, both raster and vectoring ones. Geolink includes vector and raster editors to handle the symbols and to create user's own filling and strike patterns. True Type fonts are used for inscriptions on maps. When necessary, fonts may vary for different layers, objects and scales of a map. In general, user assigns visualization attributes for all objects within a layer uniformly, meanwhile, particular objects can be supplied with different visualization attributes. Moreover, it can be done automatically, for instance, depending on object attribute values. (Thus, for example, one can visualize wells with symbols of different colors or dimensions, depending on the level of water pollution, etc.).

Fonts::

Any True Type fonts currently installed can be used in object inscriptions. Fonts of any size, shape, color and orientation are admissible. User can specify his own font for both the whole layer and/or for particular objects. Font can be changed with the map scale or, for example, according to attributive data values.

Lines, filling and strokes::

The program comes with its own set of predefined lines, fillings and strokes. User can design his own filling, stroke and line patterns using the built-in raster editor. User can import these patterns if needed. Strokes and line patterns can be used along with solid lines and fillings of any color. This approach allows creating maps with a very complex legend when, for example, strokes change conforming to one attributive data parameter and colors change conforming to the other.

Raster editor::

The built-in raster editor allows to edit line, filling, stroke and symbol patterns. It's a powerful BMP-format file editor. The editor supports both color and black-and-white patterns and symbols of arbitrary dimensions.

Vector editor::

In many cases it is more convenient to show point objects on the map using vector symbols instead of raster ones. It occurs, for instance, when user wants symbol size to be changed automatically in dependence on particular conditions, or if map exported to Windows Metafile format is to be edited with an external graphic package. A set of such symbols comes with Geolink; however, user can create his own symbols employing a built-in simple Windows Metafile editor.

Working with Attribute Data::

Object attributes can be imported along with the geographic data or entered manually or with any program later. Attribute data can be imported from some external data formats, for example from MDB (MS Access) format.

The attributes are stored in MS Access format files, however, their editing does not require a copy of this software to be installed on the computer: GeoLink allows data to be edited directly from the program, and also makes them accessible to any add-on application. Each geographic layer has its own attributive data table, and rows in this table correspond to geographic objects. It should be noted that the program allows object visualization attributes to change in dependence on their attributive data. User should simply click the object to get its attributive data.

Geographic Data Exchange Formats::

GeoLink important feature is its ability to exchange geographic data and attributes with other GIS. Users often obtain initial geographic data from different sources with no possibility to change their format.

Thus, support of basic vector and attribute information exchange formats is an absolute necessity for any GIS.

At present GeoLink maintains import/export geographic data and related attributes with MIF/MID, GEN, DXF/DBF, VEC, different MOSS versions, and some special formats. F1M format will be added to them in the nearest future. The import/export procedure can be used as a converter of geographic data.

We have to note that conversion of geographic data is a complex procedure that requires a special skill and experience. There is no standard format to exchange such data, existing formats are not compatible if we consider the type of exchange information - some support information about topological links or object legend, and other does not, etc. We did our best to make import/export operations easy without loosing their functionality.

User's Add-ons::

The GeoLink designed maps are used, first of all, as an environment for object attribute access (i.e. for implementation of info functions) and for data preparation (selection of certain territories or objects, layers, etc., user is interested in), that will be used by the special-purpose applications for solving the user's tasks. The results of data by processing these applications can, in their turn, be presented on the map, recorded, if necessary, in the geographic object database or in the object attribute database. For example, the results of hydrogeological modeling of a certain, user-selected territory can be immediately shown over the geographic situation background, and isolines built by modeling can be stored into the geographic object database.

It is worth to note the simplicity of attachment of such modules to GeoLink: they are made as Windows dynamically loaded libraries (DLL) and can be written by user since Geolink company provides all specifications necessary for that. Upon installation they become accessible immediately via separate menu items, and user can handle them as a part of the large integrated system.

Among these user's add-ons the software for editing grid data should be specially mentioned - this program presents the results of hydrogeological modeling on the map and builds isolines and equal-level zones. Another example is automatic design of a geological cross-section, which is under development at now. Most programs of the State Geological Monitoring System are among these applications.

Working with Grids::

Many of hydrogeological modeling tasks deal with spatially distributed data. As a rule, such data are represented as a matrix or finite difference model grid with a specific property value assigned to an individual cell. The model grid can have regular or variable spacing and can be geographically anchored. GeoLink GIS defines two basic terms in this context:

1. individual properties defined in the model domain, such as hydraulic conductivity or porosity, are called cartograms
2. databases that contain set of cartograms and additional information for model building are called GDB (General DataBase)

It is noteworthy that cartograms can serve both as input data for hydrogeological modeling and simulation results. GeoLink GIS integrated environment allows the user to build, maintain and display GDB-bases in easy-to-use and flexible way. You can assign arbitrary property distributions, perform routine data input in a timesaving manner, display grid data in different views including model visualization over real site map which is of a special interest for researcher. Modeling environment combines software modules for model design and data editing, powerful groundwater flow simulation tools and visualization module. Typically, the entire modeling process includes the following steps:

1. Model design using GDB-Creator that allows to:
   • create new GDB-base that can be anchored to the existing geographical database. By building GDB pattern the user defines regular or variable grid spacing. You can perform model referencing both manually by reference point and azimuth definition and graphically by moving a cartogram over the site map
   • generate new GDB on basis of the existing GDB-base pattern
   • superimpose geographic objects and their attributes on the model grid

   
    

2. Data input using data import or with specialized GDB-Editor.
    
   Data can be imported:
   • from GDB-base to GDB-base without geographical referencing
   • from GDB-base to GDB-base with geographical referencing
   • from GDB-base to GDB-base in a batch mode
   • from geographical database to GDB-base with approximation
   • from GDIR file to GDB-base with approximation
   • from Visual Modflowæ to GDB-base

   
   GDB-Editor module allows you to:

   • fill cartograms with model properties needed for groundwater flow simulation
   • view and modify several cartograms simultaneously
   • copy data from one cartogram to another
   • apply positive and/or negative masks to cartograms and perform union and intersection mask operations
   • view cartograms using "zoom-in/zoom-out" feature
   • define data array for a set of cartograms and save it for further GDB-base operations
   • build and modify cartogram legend
   • create custom-tailored scripts to automate typical cartogram calculations

   
    

3. Groundwater flow modeling with input data and simulation results stored in GDB-base. Modeling module allows to:
   • run simulation for various steady-state and transient hydrodynamic models
   • run modeling "from scratch" or on basis of previous simulation results
   • calculate total model budget
   • calculate budget for individual river basin

   
    

4. Data visualization and result interpretation features include:
   • isolines and equal-level zones plotting
   • powerful tools for cartogram legend modification
   • color-shaded cartograms printout
   • print preview, page design and other output options
   • printing to any printer or plotter supported by Windows 95/98/NT

Scope of Application::

GeoLink was created as a GIS for hydrogeologists. It means that hydrogeology (and geology, ecology etc.) requirements dominated when the system was under development.

For example, a GIS for hydrogeologists must have a powerful tool for creating map legends and must allow working with grids. On the other hand, most of applications that work in GeoLink environment are hydrogeological applications (e.g. ground water monitoring system or hydrogeology modeling software). However, the functionality of GeoLink allows this GIS to resolve problems in many areas of human activity. We can say that it's really a multipurpose GIS.

Though there are some restrictions. The first one - GeoLink isn't an urban GIS. User can solve some typical urban problems with it, but it is easier to handle the most complex (and most typical) of them using any of existing specialized urban GIS. The second one - there are only a few raster functions in GeoLink. User can work with rasters; for example, the vectorization of raster layers is possible, but if user works chiefly with rasters he should better look for a specialized package. The third - there is no possibility of automatic vectorization in GeoLink GIS (however there is a powerful vector editor).