The InSAR Norway map service is an interactive website for navigating, visualising and using ground movement data collected using satellite-based radar images and the InSAR (Interferometric Synthetic Aperture Radar) mapping technique. The following sections explain the structure and main functions of the map service.
What are the functions of the map service?
Users can easily navigate to an area of interest in this map service. The points show the annual average movement (mm/year), measured along the satellite's line of sight (LoS). Negative mean velocity values are away from the satellite, while positive mean velocity values are towards the satellite.
The map service has five main elements, as seen figure below: the map viewer, the north arrow, the coordinates, the map layers and the toolbar:
• Map viewer: The map can be viewed in either 2D or 3D by selecting the custom element of the toolbar. 3D view mode is especially useful for analysing mountainous areas.
• North arrow: In 2D, the north arrow always points upwards, but in 3D mode, the north arrow automatically adjusts as the user navigates the terrain.
• Coordinates: Once zoomed in, select an area of the map viewer, and you will find coordinate and elevation values at the bottom of the web page. The default coordinate system is WGS84. If you click on coordinates, the projection changes to UTM. (Note: If a point is selected, the time series window will be displayed).
• Datasets and map layers: From the top left, users can select InSAR data, background maps, and additional map layers they want to visualise in the map viewer.
• Toolbar: The bar at the top right includes tools useful for navigating, visualising and analyzing data.
In the toolbar on the top right (as shown in figure A), the user will find the following options: A. Search for place names, street names, or coordinates. B. Information. C. Add external WMS layers to the map service. D. View dataset legend. D. Set the light direction according to the viewing angle and viewing direction. E. Show your position on the map. F. Create a URL link with the current map view G. Switch between 2D/3D view. H. Draw a polygon for averaging InSAR time series. I. Show/hide toolbar.
How to navigate the map?
You can zoom, pan, tilt, rotate the InSAR map. 3D viewing is the default. In 2D view, you can zoom in/out and pan left/right and up/down. All possible actions are summarised in the table below.
The toolbar includes a geographic search function that quickly zooms to a specific area of interest based on place names, street names, or latitude/longitude coordinates.
| Action | Mouse | Type | Gestures (using the touchpad) |
| Zoom in/out (2/3D view | Scroll the mouse wheel or scroll with the trackpad. | W, S | Stretch/pinch with two fingers |
| Pan left/right (2/3D view) | Click-and-drag | A, D | Drag with one finger |
| Pan up/down (2/3D view) | Click-and-drag | Q, E | Drag with one finger |
| Tilt (3D view) | Click-and-drag with the right mouse button while holding down the shift button. | - | Move two fingers up or down |
| Rotate (3D view) | Click-and-drag with the right mouse button while holding down the shift button | Move two fingers in a circle | |
| Start/end free flight mode | - | Alt + G | - |
What map layers are found in the map service?
Select the menu icon on the top left to view datasets/map layers available in the map service. You will find the layers are organized into folders. The three datasets for InSAR ground motion measurements (ascending and descending satellite) are outlined in red in the figure below. They are labeled Radarsat-2 Deformation, Sentinel-1 Deformation and Sentinel-1 Deformation (old). A detailed explanation and comparison of ascending and descending data can be found here.
Other basemaps and geological maps are available (outlined in blue in the figure below) that can be selected in the map service and viewed together with the InSAR ground motion datasets. The base maps are retrieved with WMS from various agencies. More information on the content of these layers can be found on Geonorge.
A complete list of available datasets and descriptions can be found here.
How can InSAR maps be visualised?
When you select an InSAR dataset from the menu to the left (see item A in the figure below), ground motion information is displayed. The colour of the point represents its average velocity, which is defined in the legend (B in the figure below). The «settings window» (C in the figure below) can be used to adjust the appearance of ground motion points just for the layer selected. Click on an InSAR point to open the time series view (plotter) and find the entire data series and information about the measurement properties (E in the figure below). The location of the active point is indicated by a white circle in the map viewer (D in the figure below).
The data selection window shows all viewable layers. To select an InSAR layer, click the icon that is left of dataset name (A in the figure below). A cross indicates that the layer is not selected (B). When you click datasets or triangles on the right (C in the figure below), a settings window opens where you can change visualization parameters only for this layer.
It is possible to change the transparency of the layer, the size of the points, the colour table and limit values used to visualize the average speed of InSAR points (D-G in the figure below).
How to visualize InSAR time series?
The time series viewer opens when you click on a selected point or after you draw a polygon. (Find polygon icon far right on the toolbar, draw and double click to finish).
The time-series viewer consists of various elements to reveal measurement properties, a detailed view of data series and to plot ground motion (y-axis) against time (x-axis). In the figure of the below you can see:
- A: The top left of the time series viewer provides basic information: the dataset name, point ID, coordinates, average speed, coherence (InSAR quality measure - between 0 and 1 where higher values are better). Read more details.
- B: The measurement geometry is found on the upper right: LoS incidence angle, track angle and the azimuth angle. Read more details. To visualize these values two figures are shown with arrows illustrating the radar's LoS in the vertical east-west plane (U/D = Up and Down) and the horizontal plane (north-south/east-west). (more info about it here).
- C: By default, the window shows the entire time series in the documented period (x-axis) with the full range of motion values (y-axis). The pointer is interactive which makes it possible to zoom in/out on the graph by scrolling with the mouse wheel or trackpad. To scale only the y-axis, zoom in/out while pressing the "Shift" key. Limit values can also be changed at the bottom of the pointer and the "Fit" button makes it possible to return to standard visualization (the entire series).
- D: It is possible to compare time series from different places by clicking on two or more points on the map while pressing the «Shift» key. The time series window is updated with information from the last point (green points in the figure) while retaining the first series on the same graph (red points in the figure).
The time series can be visualized with simple points for each date of data acquisition (A in the figure below). It is also possible to link each acquisition date with a line (B in the figure below).
When you click on “View data” at the bottom right of the time series window (A in the figure below), an additional window opens showing all data related to the selected point (B in the figure below).
The list includes information about the point's coordinates, measurement geometry, measurement quality/reliability, as well as the entire series of motion values (mm) for each time of satellite recording. The description of the parameters can be found here.
Several best-fit features can be used to analyze the main movement trend throughout the documented period. The best-fit line is plotted when selecting the "Linear" function at the bottom of the time series viewer. When movements show a nonlinear pattern, other functions can be used, e.g. "Polynomial".
In the map viewer, you can also draw polygons. Within this range (the polygon), an average of the InSAR measurements is calculated and the result is plotted in the time series window.
The data information at the top left of the time series viewer indicates the number of measurements used to plot the average series.
How to share or download data?
It is possible to create a sharable URL link with the current map view by clicking on the square icon in the toolbar (the top right of the map service, A in the figure below). The link can be saved/shared to return to the same place and with the same visible layers later.
Detailed information about a single point or the average of several points is obtained by clicking on «View Data» in the plot window and can be downloaded at the end of the series (CSV button, B in figure below). To download data for multiple points selected in a drawn polygon, use the green button marked "CSV" at the bottom of the plot window. The dataset for the selected point or multiple selected points will then be downloaded as a .csv file. To save the figure (time series plot), press «Generate SVG» at the bottom of the plot window (D in the figure below). The entire time series window is saved as a .svg file.
Data from InSAR Norway is also available through an "Application Programming Interface" (API). For access to this data and more information contact John Dehls or Marie Bredal.
