Frequently Asked Questions (FAQ)

General navigation

The FAQ, the Contact details, or the Impressum of the page can be accessed through buttons in the footer or buttons above the map search on the left side.


The user menu could be founded in the top right corner of the application. By clicking the respective flag you can choose the language of the Virtual Map Forum 2.0. If logged in (could be done through clicking on the login button) you can also access your personal georeference history and an overview over unreferenced maps. Further you can change here to full-screen-mode by clicking the arrow-button.

Map detection

Using the navigation directly on the map or through the input of a place name in the search field of the spatiotemporal search module (left part / main page) you can choose the relevant spatial area. The spatiotemporal search module also displays the relevant search results for your spatiotemporally selected criteria. Through using the time slider you can also adjust the relevant time period for your search results.

Search for place


If you type in the input box a place name the application offers you a select list of possible place names. By choosing a place name from this list with your mouse or the keyboard the map jumps right to this place.

Adjust the time


With the help of the time bar you can adjust the period of your search time. The max-/min-years represent therefor the maximum range of time. The adjusting of the search period affects the listed results in the search list.

The search list


The search list displays all available maps for the appropriate search criteria (time, space, facets). The header of the search list shows the number of search hits. Beneath, you can sort the results by pressing the buttons Title or Time. If you click on a search result, the appropriate historical map will be displayed on the main map and automatically be transferred to the "My Maps" map container.

Every single search result will be displayed with its name, time (dating) and its scale. Furthermore there will be given a thumbnail image of the relevant map. If you move your mouse over a search result, the spatial expansion of the map will be represented in a polygon on the main map.

Map navigation


The picture left hand side shows the different navigation tools which can be used on the maps.

By pressing the + or the - you can zoom into or out of the map (you can also use the mouse wheel)

The Magnifier button activates a map magnifier. If you move it over a historical map it will show the recent OpenStreetMap for this part. Press y and the area for the magnifier gets bigger. Press x and the area gets smaller.

Press and hold the Shift key and press and move the mouse at the same time you rotate the map. Press the Needle button the map will be "northed" again.

The button with the cross allows you to create a sharing link of the current map view as well as to activate the illustration of the actual lat / lon position of the map.

The last button gives the opportunity to toggle between 2D and 3D view. The 3D views allows the projection of historic maps on top of a 3D terrain model ( STK World Terrain. Through holding CTRL and the left mouse button the user can navigate throught the 3D view and adjust the camera perspective.

Manage chosen maps


If you choose a map in the spatiotemporal search module it will be added automatically to the main map and to the map management container. In this map management container you can change the transparency of maps, activate and deactivate maps, you can add related maps, delete any map from your own selection and it is possible to change the order of the presentation of the maps on the main map.

Change transparency


If you click with your mouse on the bar and slide it up- or downwards you can change the transparency of the chosen map. This will help you to see the changing in the landscapes and to check the georeferencing of your map.

Activate / deactivate maps


By clicking with your mouse on the green square you can either activate or deactivate the corresponding map sheet.

Reorder maps


To reorder maps use your mouse cursor. Click on the thumbnail version of one map sheets in your "My Maps" map container and press and hold it. Then you can easily move it up- or downwards in the container to change the order of the map sheets.

If you want to have a map at the very top you can either use the drag- and-drop method or you can just click on the symbol above the activate / deactivate switch. So the map you just clicked on will automatically be moved to the top of the list.

Original maps

If you selected one map from the plane survey sheet search list by clicking on it and then click on the corresponding square in the main map you will get further information about the map sheet. You will also be given a picture of the original map sheet.

Georeferencing of Maps

The Virtual Map Forum 2.0 gives access to a wide range of historic maps, which are waiting for georeferencing. As a user you can thereby help us in this process.

Basically you have to set ground control points, which are a prerequisite for the usage of different transformation algorithms. Further you can draw a clip polygon, which is used to clip away the unnecessary edge of the georeferenced maps. The following video gives a short overview over the georeferencing process.

To participate in the georeferencing process of the historic maps you have to sign up in the Virtual Map Forum 2.0.

Map selection


In the user menu you can open an list of unreferenced maps by clicking on point "Show unreferenced maps". The displayed lists give you than also an option for performing an subselection of the unreferenced maps by title in the input field. By clicking on the "Georeference" button of a given map record you will be forwarded to the georeference view. Further you can open your personal georeference history by clicking on the "Georeference History" point.



For apply transformation algorithms to the historic map image, ground control points (gcp) are needed. A ground control is composed of a point on the unreferenced image (left side) and the corresponding point on the georeferenced map (right side). Depending on the used transformation algorithm more or less ground control points are used (e.g. affine > 4 gcp). Based on a validation result also a clip polygon can be drawn. The clip polygon can than be used for clipping away the unnecessary edge content.

The toolbox on the unreferenced image viewer (left side) holds different tools for drawing, moving and deleting ground control points.

For setting a ground control point choose the tool Set ground control point and then click on the unreference image (left side) and the corresponding place on the georeferenced image (rigth side). If a point was set wrong, you can adjust the position by using the tool Move ground control point and move the corresponding point by drag&drop. If you wanna remove a ground control point use the tool Delete ground control point.

By using the tool Move map you can move the map to the wanted view.


If enough ground control points have been set, a validation image can be produced by the clicking on the Update Preview button. It is also possible to switch the used transformation algorithm. Generally it is recommended to use an "Affine" transformation for geological maps or plane survey sheets and a minimum number of 4 ground control points. In case of older historic maps types a "TPS" transformation is recommended. There you can always increase the georeferencing quality by adding more ground control points.


On the basis of a georeferenced validation results a clip polygon can be drawn. Therefor use the tool Draw Clip Polygon on the georeferenced map view.

The captured georeference paramater could be saved permanently by using the button "Confirm Georeferencing". This will navigate the user back to the main page and save the georeference result permantly. After a view minutes the new georeference results are also accessible through the web client by all users.

For more information please refer to the Video link further above or contact us.