Satellite missions such as SPOT-VEGETATION and PROBA-V have been capturing the earth on a daily basis for more than 15 years. This has accumulated into a treasure trove of information on how regions in the world have evolved over this period. However, it has not always been easy to quickly extract useful information out of this archive, until now!
One of the applications offered in the PROBA-V Mission Exploitation Platform, is the 'Time Series Viewer'. This application unlocks the information in remote sensing archives, by enabling interactive querying on precomputed time series datasets. We have selected the following levels of aggregation to be available:
- All CCI landcovers for GAUL level 1 administrative regions, for instance: grassland in provinces or states of a country.
- GAUL level 1 administrative regions
- All CCI landcovers for all countries of the world (GAUL level 0)
- All countries of the world.
Next to the information on the precomputed levels it is possible to request the information at the level of individual pixels. The information will be calculated on-the-fly and shown in the charts.
Regions on the map are colored according to the average value for a given date, other charts also depend on the selected date. Hence it is important to know how to select a date. This can be done by dragging the scrollbar of the chart in the bottom right corner, which is shown by default. This process is shown in the following video.
Observe how the date in the upper left corner of the map changes, while the scrollbar at the bottom right is dragged. The red line on this graph also indicates the currently selected date.
Note that the panel at the left also has a 'Time' tab, which allows you to jump directly to a given year. You can also use the buttons on the overview chart to select a time range. The center of the selected time range is used to determine the current date on the map.
You can select a point on the map for requesting the information at the level of an individual pixel.
Click once on the icon in the left upper corner of the map. Move the cursor and a blue spot will follow your cursor. Click a second time with the cursor placed on the requested point. A marker is placed on the map and the geographical information about the selected point is shown in the list (left under).You can update the name for the point in the list. This approach can be repeated for placing multiple points.
The process of selecting a point is shown in the following video:
The requested information on the selected point(s) will be calculated on-the-fly and shown in the charts.
Note that this feature is only availble for the PROBA-V S10 TOC NDVI and rainfall data.
Comparing multiple regions/landcovers
To compare the profile for e.g. the NDVI parameter for the currently selected year amongst the regions of a country, you can use the 'Charts per region' tab. This tab will show a chart per region in a country. It also supports drilling down to the level of landcover, hence allowing you to compare the profile of different landcovers of the selected region, to do this, simply click on the chart of a given region. Use the 'Up' button at the top to go back to all regions for that country.
Finally, the 'Filter' menu can be used if you want to select the regions to compare in a country. All of this is shown in the following video:
Control panel of the Application
From the left part of the application, you can indicate which data you want to be shown on the map and the graphs.
For products with a long date-range, it is possible to show the difference with the LongTerm Average instead of the actual value on the map.
Indicate whether the yearly chart should show data from January till December, or from July till June.
Indicate whether the chart should show the streets overlay. This combines the chart with the OpenStreetMap layer to show the geographic information which can be really helpful when selecting a point.
Select the information to be shown on the map (by using ) or the graphs (by using ). On the graph different layers can be shown concurrently, but the map can only display one layer. With the 'MaxY' parameter, your can set the maximum value on the vertical axis of the chart.
As rainfall layer, the data from the CHIRP (Climate Hazard Group InfraRed Precipitation) service is used. More information can be found on http://chg.geog.ucsb.edu/data/.
Select a year. Remark that this can be done more easily using the slider on the right graph.
Select a country. Remark that this can be done more easily by clicking in a country on the map.
Select a region within a country. Remark that this can be done more easily by zooming on the map until the regions become visible and then clicking in a region on the map.
The Admin level 1 refer to the GAUL Level 1 regions. More information on GAUL (Global Administratieve Unit Layers) can be found here: http://www.fao.org/geonetwork/srv/en/metadata.show?id=12691.
When a country is selected, this list will show all land cover types which are present in that country. when hoovering your mouse pointer over the land cover value in the list, you'll see on the map where this land cover occurs.
Select here a LandCover to update the chart, containing only data for that specific landcover in the country/region.
The Land Cover values as defined by the ESA Climate Change Initiative (CCI) are used here. More information can be found on http://www.esa-landcover-cci.org/.
This video show how the landcover is visualized on the map when hovering over the list:
This area shows a list with all the points selected and all the polygons drawn on the map, together with the coordinates and a name.
You can update the name, make the point/polygon invisible on the map and the charts or delete it when it is no longer needed.
The data shown in the graphs can also be exported for further analysis. The timeseries graph has a menu button in the top right corner which supports this: