The Gravity Information System
First steps
Overview (Key Map)
The key map serves as a survey of the map navigation.
A red square or a small cross shows the particular position of
the main map on the world map.
By a mouse click into the key map you can select a continent that
will be loaded in the main map.
Continent selection
Instead of clicking into the key map you can also select a continent
from this selective list. It is recommended to start the map navigation
with a continent since it gives a better survey and it saves some loading time.
Map extent
The four input fields (North, West, East, South) indicate the particular
extent of the main map in geographical coordinates [º].The 'North' and the 'South'
give the minimum and maximum latitude, the 'West' and the 'East' specify the
extreme values for the longitude.
The fields will be refreshed automatically after selecting a new map area.
To select a certain map area by coordinates change the values manually and click the OK-button.
Map size
The rectangle of the main map is set to a medium size of 600*420 pixel by default.
With this map size the full view of this web page is optimized to a monitor resolution
of 1024*768 or 1152*864.
If you use a different monitor resolution and the main map appears to be too small or too large
then you can fit the map size by selecting a value from the drop down list.
It is recommended to zoom in to a smaller area at first to lessen the loading time.
Map legend
The map legend appears in an extra box below the main information box on the left hand side.
It includes the main information about the thematic background layer with a coloured scale
and the optional contour lines.
Further information to the map can be found in the upper right corner
of this page with the map coordinates to the mouse pointer and with an approximated scale factor.
Below the main map a scalebar in metric units may used to estimate distances.
The appearance of the map can be changed under the topic 'Map layer'.
Selection of a thematic layer
The basic illustration of the main map can be configured by the selection of a thematic layer.
In order to select a thematic background click on a symbol 
from the layer's list and mark the white box 
.
This setting clears the previous background selection since only one background can be set.
If the present background marker is cleared the Base map layer is selected automatically.
Activate the new settings by pressing the REFRESH button below.
The selection of a contour line layer is optional but it can only be one of these layers set per map view.
Selection of topo layers
The box Topo layer contains a list of map features that illustrate the local topographical or political chararcteristics.
By default the single features are activated or deactivated automatically depending on the map scale.
Location
City search
Result
Selection of the type of instrument
Optional inputs
Legend
Measuring a distance
Otaining an area
Zoom in
Zoom out
Recenter the map
Full extent
Thematic map layer
Gravity point selection
Approx. gravity for a city
Gravity zones for weighing instruments
Calculation of distances
Calculation of areas
Gravity data
Height data
Map data
Math procedures
Development