GAP Help

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The Groundwater Assessment Platform (GAP; hosts information on geogenic contamination of groundwater by arsenic and fluoride. It provides the possibility to share data, case studies and field experiences as well as to interact with other users and create probabilistic maps for any area on the globe. The site has two main sections (Figure 1). In GAP Maps, you can display and print existing data and models as well as manipulate and model your own data and create hazard maps. The GAP Wiki contains diverse information on geogenic contamination.

The Help section provides instructions for using the GAP Maps section.

Figure 1: Entry page

Viewing geospatial data (without registration)

All of the publicly available maps and data can be viewed and printed without registering on the site.

Click on New data public.png to open a list of all available layers. Click on New print.png to print the currently viewed map as a PDF.

In case you have questions or require help while using the site, you can click on Help in the top bar to open the help page, which explains all of the features of GAP Maps. Alternatively, click the question mark New question.png in the upper-right corner of any window to open the help page relevant to that window.

In order to access the full functionality of GAP, you must first register as a user.

Main Page

Viewing geospatial data and developing models (with registration)

To be able to upload your own data and create models, you must register or log in in the upper-right of the screen. This makes the full functionality of the site available.

The main functions of GAP Maps contained in the toolbar (1) on the left side of the screen. These functions are explained in detail in the sections: Layer list, My Layers, Statistical Analysis, Community and Print.

Additional map tools are located in the upper-right of the screen (2): Base Layers, Get point information and Zoom in/out

Main Page


Click Register in the upper-right of the screen to create a new account using your e-mail address. You must confirm that you are in full agreement with the 'Terms of Use' in order to complete the registration.


New data public.png Layer list

Layer list

The Layer list tab lists the Active Layers as well as all available layers, which are grouped into the categories GAP layers, Publicly shared layers and Shared layers.

Active Layers lists the layers that have been added to the map. The layers can be turned on or off by clicking the layer name. Hovering the mouse over the layer name opens a popup window containing the layer legend and a slider bar to adjust the layer's opacity as well as buttons to move the position of a layer up or down, zoom to its extent or remove it

GAP layers contains GAP prediction maps and data points as well as environmental datasets, such as geology, climate and soil, made publicly available from other sources.

Publicly shared layers lists those layers that GAP users have shared publicly.

Shared layers lists those layers that have been shared personally with you, either directly from another user or as part of a community.

There are three data types: Coverage, Polygon and Point. To add a layer to the map, click the layer name. Click New info.png next to a layer to display its source and a description of the data.

Data Types
Data type Icon
Coverage Raster.png
Polygon Polygon.png
Point Bullet blue.png

My layers icon.png My Layers

The My Layers window lists all layers uploaded by the user. It also includes functions to add, remove, share, display, download and manipulate the symbology of layers.

A tutorial on this part of the site is available in the video below.

My Layers


Functionality for uploading geospatial data layers to the map. Click here for detailed instructions.


To remove a layer, select it in the table and click Remove.


Functionality to share/unshare a layer with an individual user, a community or all users (Public). Click here for a detailed information.


To display a layer (add layer to map), either double-click the layer name in the table, or select layer in the table and click Display.


Functionality for changing a layer's symbology. Click here for detailed instructions.


Click Download to save a copy of a layer as a GIS-compatible shapefile or tif.


Click Rename to change the name of one of your layers.

Statistical analysis icon.png Statistical Analysis

The Statistical Analysis section provides functionality for developing statistical models and probability maps. Click here for detailed information.

Community icon.png Community

Community (left) and <b>Community Layers (right)

The Communities window lists the communities to which a user belongs.

The Create button opens a window to create a new community. You must enter a name for the community and optionally a topic or description.

The Remove button removes the selected community, which is possible only if you have administrative rights.

The Layers button opens a window that lists all community layers according to community. Double-click a layer to add it to the map.

The Members button allows you to add and remove members by e-mail address and change their administrative rights.

The Messages button allows you to send and view messages for the community.

With the Edit button, you can change the name, topic and description of a community to which you have administrative rights.

Manage account icon.png Manage Account

Manage Account Manage account icon.png lets you change your password / login preference or delete your account.

New print.png Print

Click New print.png to print the displayed map as a PDF. Assign a map title and select the page layout (portrait or landscape) and resolution (DPI). Note that if the background map is displayed, the resolution of the printed map will be limited to 90 DPI. Click Submit when finished.


Base Layers

Base Layers are accessed by clicking the Base layers icon 60.png icon in the upper right. Five different base maps are offered: Bing Roads, Bing Aerial, Google Maps, Open Street Maps and a Country borders.

Base layers

Get point information

Click on Get point info icon.png to access the Get point information tool, which allows you to find the values of all active layers at a point.

Get point information

Zoom in/out

Click Zoom in icon.png to zoom in or Zoom out icon.png to zoom out. Alternatively, you can zoom the map in or out with the scroll wheel of your mouse.

New question.png Help

Click New question.png for content-specific help.