Visual comparison of EO data and Products
Compare pre and post event images
The ESA Charter Mapper offers multiple visualization tools. As an example, to enhance the visualization of multiple layers, the geobrowser also provides a Vertical Slider Bar to combine two images (e.g. pre- and post-event). This is possible by selecting from the Results panel two features (e.g. two Calibrated Datasets) having active tiled layers.
A product with tiled layer active (e.g. when for a Dataset an overview is visible in the map) has the world icon . For more information please refer to the section of the user manual about the Geobrowser Layout.
To visually compare two images from the Results panel select a pair of features and click on Compare Layers. More information about how to activate image comparison slider bar for a pair of Datasets can be found here.
Figure 1 - Compare Layers function and visual comparison of a pair of PlanetScope data products with the vertical slider bar in the ESA Charter Mapper (Image credit: Planet).
Compare EO data and Products via the Feature Basket
In the ESA Charter Mapper it is also possible to visually compare the results obtained from a processing service (e.g. the NDVI from the OPT-Index processor) with a single-band asset or an overviw product (e.g. Color Infrared Vegetation RGB composite) from the calibrated EO data employed as input of the same processing service (e.g. Color Infrared Vegetation (CIV) overview from TOA reflectance).
In order to compare the Spectral Index with the original image, it is useful to have the product displayed over the satellite imagery. This can be done using the Feature Basket function available in the ESA Charter Mapper. More information about the Feature Basket function can be found here.
First step is the identification of a suitable EO data to be processed over an AOI, e.g. a Kompsat-3 multispectral Calibrated Dataset.
Figure 2 - Color Infrared Vegetation (CIV) overview from Kompsat-3 data over the Russian Federation (Image credit: KARI).
Once the image of interest is identified, it is worth to drag and drop from the Results tab the Dataset direclty into the Feature Basket. This preliminary step will facilitate the retrieval of the EO data in the following steps and will be a reference location for future use of the same Dataset.
Figure 3 - The drag and drop of a Kompsat-3 Calibrated Dataset from the Results panel into the Feature basket (Image credit: KARI).
Later the OPT-Index processor can be executed by setting as input reference the same dataset include in the Feature Basket. More information about the Optical Spectral Index service function can be found by looking at the OPT-Index tutorial as well as the OPT-Index service specifications. Once the job is succeded the Result will be accessible under the Result panel in the left by clicking on the My Results bottton in the Data Context Menu or by clicking on Show results under the Processing Result tab in the right panel of the interface.
Figure 4 - Red-Cyan RGB composite from NDVI (Red) and NDWI (Cyan) indexes derived from Kompsat-3 data over the Russian Federation (Image credit: KARI).
The Result of the OPT-Index can be also included into the Feature Basket where the source calibrated Dataset is stored. To do so simply drag and drop the layer under Products from the Results tab into the Feature Basket.
Figure 5 - The drag and drop of a Spectral Index Product derived from a Kompsat-3 Calibrated Dataset from the Results panel into the Feature basket (Image credit: KARI).
After that by opening the Feature Basket only the two Products (Calibrated Dataset and Spectral Index Product) cointaned in the basket will appear in the map as shown in Figure 6.
Figure 6 - An example of Spectral Index Product and source Calibrated Dataset stored into the Feature Basket (Image credit: KARI).
Once in the Feature Basket the user can also visually compare NDVI with the TOA reflectance by selecting the two layers and clicking on the Compare Layers funtion. A vertical slider bar will appear as shown in Figure 7.
Figure 7 - Visual comparison of Red-Cyan composite of NDVI and NDWI with the CIV overview using the slider bar in the ESA Charter Mapper (Image credit: KARI).
In a similar manner to better assess vegetated areas, a binary mask in green obtained from the Advanced Multi Sensor Composite (COMBI-Plus) service can be also visually compared with the Color Infrared Vegetation RGB composite obtained from the same Kompsat-3 data. More information about the Advanced Multi Sensor Composite service function can be found by looking at the COMBI-Plus tutorial as well as the COMBI-Plus service specifications.
These products can also be saved into a Data Package to be shared among authorized users (e.g. from PM to a VA). The procedure for the creation of a Data Package in the ESA Charter Mapper from the two selected features of the Calibrated Dataset and the Spectral Index product from Kompsat-3 data is shown in the below Figures 9 and 10.
Figure 9 - The procedure for the creation of a Data Package in the ESA Charter Mapper from selected features in the Feature Basket (Image credit: KARI).
Figure 10 - The Data Package tab showing the Data Package just created from Kompsat-3 data in the ESA Charter Mapper (Image credit: KARI).